Geography functions

GoogleSQL for BigQuery supports geography functions. Geography functions operate on or generate GoogleSQL GEOGRAPHY values. The signature of most geography functions starts with ST_. GoogleSQL for BigQuery supports the following functions that can be used to analyze geographical data, determine spatial relationships between geographical features, and construct or manipulate GEOGRAPHYs.

All GoogleSQL geography functions return NULL if any input argument is NULL.

Categories

The geography functions are grouped into the following categories based on their behavior:

Category	Functions	Description
Constructors	ST_GEOGPOINT ST_MAKELINE ST_MAKEPOLYGON ST_MAKEPOLYGONORIENTED	Functions that build new geography values from coordinates or existing geographies.
Parsers	ST_GEOGFROM ST_GEOGFROMGEOJSON ST_GEOGFROMTEXT ST_GEOGFROMWKB ST_GEOGPOINTFROMGEOHASH	Functions that create geographies from an external format such as WKT and GeoJSON.
Formatters	ST_ASBINARY ST_ASGEOJSON ST_ASTEXT ST_GEOHASH	Functions that export geographies to an external format such as WKT.
Transformations	ST_BOUNDARY ST_BUFFER ST_BUFFERWITHTOLERANCE ST_CENTROID ST_CENTROID_AGG (Aggregate) ST_CLOSESTPOINT ST_CONVEXHULL ST_DIFFERENCE ST_EXTERIORRING ST_INTERIORRINGS ST_INTERSECTION ST_LINEINTERPOLATEPOINT ST_LINESUBSTRING ST_SIMPLIFY ST_SNAPTOGRID ST_UNION ST_UNION_AGG (Aggregate)	Functions that generate a new geography based on input.
Accessors	ST_DIMENSION ST_DUMP ST_ENDPOINT ST_GEOMETRYTYPE ST_ISCLOSED ST_ISCOLLECTION ST_ISEMPTY ST_ISRING ST_NPOINTS ST_NUMGEOMETRIES ST_NUMPOINTS ST_POINTN ST_STARTPOINT ST_X ST_Y	Functions that provide access to properties of a geography without side-effects.
Predicates	ST_CONTAINS ST_COVEREDBY ST_COVERS ST_DISJOINT ST_DWITHIN ST_EQUALS ST_INTERSECTS ST_INTERSECTSBOX ST_TOUCHES ST_WITHIN	Functions that return TRUE or FALSE for some spatial relationship between two geographies or some property of a geography. These functions are commonly used in filter clauses.
Measures	ST_ANGLE ST_AREA ST_AZIMUTH ST_BOUNDINGBOX ST_DISTANCE ST_EXTENT (Aggregate) ST_HAUSDORFFDISTANCE ST_LINELOCATEPOINT ST_LENGTH ST_MAXDISTANCE ST_PERIMETER	Functions that compute measurements of one or more geographies.
Clustering	ST_CLUSTERDBSCAN	Functions that perform clustering on geographies.
S2 functions	S2_CELLIDFROMPOINT S2_COVERINGCELLIDS	Functions for working with S2 cell coverings of GEOGRAPHY.

Function list

Name	Summary
S2_CELLIDFROMPOINT	Gets the S2 cell ID covering a point GEOGRAPHY value.
S2_COVERINGCELLIDS	Gets an array of S2 cell IDs that cover a GEOGRAPHY value.
ST_ANGLE	Takes three point GEOGRAPHY values, which represent two intersecting lines, and returns the angle between these lines.
ST_AREA	Gets the area covered by the polygons in a GEOGRAPHY value.
ST_ASBINARY	Converts a GEOGRAPHY value to a BYTES WKB geography value.
ST_ASGEOJSON	Converts a GEOGRAPHY value to a STRING GeoJSON geography value.
ST_ASTEXT	Converts a GEOGRAPHY value to a STRING WKT geography value.
ST_AZIMUTH	Gets the azimuth of a line segment formed by two point GEOGRAPHY values.
ST_BOUNDARY	Gets the union of component boundaries in a GEOGRAPHY value.
ST_BOUNDINGBOX	Gets the bounding box for a GEOGRAPHY value.
ST_BUFFER	Gets the buffer around a GEOGRAPHY value, using a specific number of segments.
ST_BUFFERWITHTOLERANCE	Gets the buffer around a GEOGRAPHY value, using tolerance.
ST_CENTROID	Gets the centroid of a GEOGRAPHY value.
ST_CENTROID_AGG	Gets the centroid of a set of GEOGRAPHY values.
ST_CLOSESTPOINT	Gets the point on a GEOGRAPHY value which is closest to any point in a second GEOGRAPHY value.
ST_CLUSTERDBSCAN	Performs DBSCAN clustering on a group of GEOGRAPHY values and produces a 0-based cluster number for this row.
ST_CONTAINS	Checks if one GEOGRAPHY value contains another GEOGRAPHY value.
ST_CONVEXHULL	Returns the convex hull for a GEOGRAPHY value.
ST_COVEREDBY	Checks if all points of a GEOGRAPHY value are on the boundary or interior of another GEOGRAPHY value.
ST_COVERS	Checks if all points of a GEOGRAPHY value are on the boundary or interior of another GEOGRAPHY value.
ST_DIFFERENCE	Gets the point set difference between two GEOGRAPHY values.
ST_DIMENSION	Gets the dimension of the highest-dimensional element in a GEOGRAPHY value.
ST_DISJOINT	Checks if two GEOGRAPHY values are disjoint (do not intersect).
ST_DISTANCE	Gets the shortest distance in meters between two GEOGRAPHY values.
ST_DUMP	Returns an array of simple GEOGRAPHY components in a GEOGRAPHY value.
ST_DWITHIN	Checks if any points in two GEOGRAPHY values are within a given distance.
ST_ENDPOINT	Gets the last point of a linestring GEOGRAPHY value.
ST_EQUALS	Checks if two GEOGRAPHY values represent the same GEOGRAPHY value.
ST_EXTENT	Gets the bounding box for a group of GEOGRAPHY values.
ST_EXTERIORRING	Returns a linestring GEOGRAPHY value that corresponds to the outermost ring of a polygon GEOGRAPHY value.
ST_GEOGFROM	Converts a STRING or BYTES value into a GEOGRAPHY value.
ST_GEOGFROMGEOJSON	Converts a STRING GeoJSON geometry value into a GEOGRAPHY value.
ST_GEOGFROMTEXT	Converts a STRING WKT geometry value into a GEOGRAPHY value.
ST_GEOGFROMWKB	Converts a BYTES or hexadecimal-text STRING WKT geometry value into a GEOGRAPHY value.
ST_GEOGPOINT	Creates a point GEOGRAPHY value for a given longitude and latitude.
ST_GEOGPOINTFROMGEOHASH	Gets a point GEOGRAPHY value that is in the middle of a bounding box defined in a STRING GeoHash value.
ST_GEOHASH	Converts a point GEOGRAPHY value to a STRING GeoHash value.
ST_GEOMETRYTYPE	Gets the Open Geospatial Consortium (OGC) geometry type for a GEOGRAPHY value.
ST_HAUSDORFFDISTANCE	Gets the discrete Hausdorff distance between two geometries.
ST_INTERIORRINGS	Gets the interior rings of a polygon GEOGRAPHY value.
ST_INTERSECTION	Gets the point set intersection of two GEOGRAPHY values.
ST_INTERSECTS	Checks if at least one point appears in two GEOGRAPHY values.
ST_INTERSECTSBOX	Checks if a GEOGRAPHY value intersects a rectangle.
ST_ISCLOSED	Checks if all components in a GEOGRAPHY value are closed.
ST_ISCOLLECTION	Checks if the total number of points, linestrings, and polygons is greater than one in a GEOGRAPHY value.
ST_ISEMPTY	Checks if a GEOGRAPHY value is empty.
ST_ISRING	Checks if a GEOGRAPHY value is a closed, simple linestring.
ST_LENGTH	Gets the total length of lines in a GEOGRAPHY value.
ST_LINEINTERPOLATEPOINT	Gets a point at a specific fraction in a linestring GEOGRAPHY value.
ST_LINELOCATEPOINT	Gets a section of a linestring GEOGRAPHY value between the start point and a point GEOGRAPHY value.
ST_LINESUBSTRING	Gets a segment of a single linestring at a specific starting and ending fraction.
ST_MAKELINE	Creates a linestring GEOGRAPHY value by concatenating the point and linestring vertices of GEOGRAPHY values.
ST_MAKEPOLYGON	Constructs a polygon GEOGRAPHY value by combining a polygon shell with polygon holes.
ST_MAKEPOLYGONORIENTED	Constructs a polygon GEOGRAPHY value, using an array of linestring GEOGRAPHY values. The vertex ordering of each linestring determines the orientation of each polygon ring.
ST_MAXDISTANCE	Gets the longest distance between two non-empty GEOGRAPHY values.
ST_NPOINTS	An alias of ST_NUMPOINTS.
ST_NUMGEOMETRIES	Gets the number of geometries in a GEOGRAPHY value.
ST_NUMPOINTS	Gets the number of vertices in the a GEOGRAPHY value.
ST_PERIMETER	Gets the length of the boundary of the polygons in a GEOGRAPHY value.
ST_POINTN	Gets the point at a specific index of a linestring GEOGRAPHY value.
ST_SIMPLIFY	Converts a GEOGRAPHY value into a simplified GEOGRAPHY value, using tolerance.
ST_SNAPTOGRID	Produces a GEOGRAPHY value, where each vertex has been snapped to a longitude/latitude grid.
ST_STARTPOINT	Gets the first point of a linestring GEOGRAPHY value.
ST_TOUCHES	Checks if two GEOGRAPHY values intersect and their interiors have no elements in common.
ST_UNION	Gets the point set union of multiple GEOGRAPHY values.
ST_UNION_AGG	Aggregates over GEOGRAPHY values and gets their point set union.
ST_WITHIN	Checks if one GEOGRAPHY value contains another GEOGRAPHY value.
ST_X	Gets the longitude from a point GEOGRAPHY value.
ST_Y	Gets the latitude from a point GEOGRAPHY value.

S2_CELLIDFROMPOINT

S2_CELLIDFROMPOINT(point_geography[, level => cell_level])

Description

Returns the S2 cell ID covering a point GEOGRAPHY.

• The optional INT64 parameter level specifies the S2 cell level for the returned cell. Naming this argument is optional.

This is advanced functionality for interoperability with systems utilizing the S2 Geometry Library.

Constraints

• Returns the cell ID as a signed INT64 bit-equivalent to unsigned 64-bit integer representation.
• Can return negative cell IDs.
• Valid S2 cell levels are 0 to 30.
• level defaults to 30 if not explicitly specified.
• The function only supports a single point GEOGRAPHY. Use the SAFE prefix if the input can be multipoint, linestring, polygon, or an empty GEOGRAPHY.
• To compute the covering of a complex GEOGRAPHY, use S2_COVERINGCELLIDS.

Return type

INT64

Example

WITH data AS (
  SELECT 1 AS id, ST_GEOGPOINT(-122, 47) AS geo
  UNION ALL
  -- empty geography is not supported
  SELECT 2 AS id, ST_GEOGFROMTEXT('POINT EMPTY') AS geo
  UNION ALL
  -- only points are supported
  SELECT 3 AS id, ST_GEOGFROMTEXT('LINESTRING(1 2, 3 4)') AS geo
)
SELECT id,
       SAFE.S2_CELLIDFROMPOINT(geo) cell30,
       SAFE.S2_CELLIDFROMPOINT(geo, level => 10) cell10
FROM data;

/*----+---------------------+---------------------*
 | id | cell30              | cell10              |
 +----+---------------------+---------------------+
 | 1  | 6093613931972369317 | 6093613287902019584 |
 | 2  | NULL                | NULL                |
 | 3  | NULL                | NULL                |
 *----+---------------------+---------------------*/

S2_COVERINGCELLIDS

S2_COVERINGCELLIDS(
    geography
    [, min_level => cell_level]
    [, max_level => cell_level]
    [, max_cells => max_cells]
    [, buffer => buffer])

Description

Returns an array of S2 cell IDs that cover the input GEOGRAPHY. The function returns at most max_cells cells. The optional arguments min_level and max_level specify minimum and maximum levels for returned S2 cells. The array size is limited by the optional max_cells argument. The optional buffer argument specifies a buffering factor in meters; the region being covered is expanded from the extent of the input geography by this amount.

This is advanced functionality for interoperability with systems utilizing the S2 Geometry Library.

Constraints

• Returns the cell ID as a signed INT64 bit-equivalent to unsigned 64-bit integer representation.
• Can return negative cell IDs.
• Valid S2 cell levels are 0 to 30.
• max_cells defaults to 8 if not explicitly specified.
• buffer should be nonnegative. It defaults to 0.0 meters if not explicitly specified.

Return type

ARRAY<INT64>

Example

WITH data AS (
  SELECT 1 AS id, ST_GEOGPOINT(-122, 47) AS geo
  UNION ALL
  SELECT 2 AS id, ST_GEOGFROMTEXT('POINT EMPTY') AS geo
  UNION ALL
  SELECT 3 AS id, ST_GEOGFROMTEXT('LINESTRING(-122.12 47.67, -122.19 47.69)') AS geo
)
SELECT id, S2_COVERINGCELLIDS(geo, min_level => 12) cells
FROM data;

/*----+--------------------------------------------------------------------------------------*
 | id | cells                                                                                |
 +----+--------------------------------------------------------------------------------------+
 | 1  | [6093613931972369317]                                                                |
 | 2  | []                                                                                   |
 | 3  | [6093384954555662336, 6093390709811838976, 6093390735581642752, 6093390740145045504, |
 |    |  6093390791416217600, 6093390812891054080, 6093390817187069952, 6093496378892222464] |
 *----+--------------------------------------------------------------------------------------*/

ST_ANGLE

ST_ANGLE(point_geography_1, point_geography_2, point_geography_3)

Description

Takes three point GEOGRAPHY values, which represent two intersecting lines. Returns the angle between these lines. Point 2 and point 1 represent the first line and point 2 and point 3 represent the second line. The angle between these lines is in radians, in the range [0, 2pi). The angle is measured clockwise from the first line to the second line.

ST_ANGLE has the following edge cases:

• If points 2 and 3 are the same, returns NULL.
• If points 2 and 1 are the same, returns NULL.
• If points 2 and 3 are exactly antipodal, returns NULL.
• If points 2 and 1 are exactly antipodal, returns NULL.
• If any of the input geographies are not single points or are the empty geography, then throws an error.

Return type

FLOAT64

Example

WITH geos AS (
  SELECT 1 id, ST_GEOGPOINT(1, 0) geo1, ST_GEOGPOINT(0, 0) geo2, ST_GEOGPOINT(0, 1) geo3 UNION ALL
  SELECT 2 id, ST_GEOGPOINT(0, 0), ST_GEOGPOINT(1, 0), ST_GEOGPOINT(0, 1) UNION ALL
  SELECT 3 id, ST_GEOGPOINT(1, 0), ST_GEOGPOINT(0, 0), ST_GEOGPOINT(1, 0) UNION ALL
  SELECT 4 id, ST_GEOGPOINT(1, 0) geo1, ST_GEOGPOINT(0, 0) geo2, ST_GEOGPOINT(0, 0) geo3 UNION ALL
  SELECT 5 id, ST_GEOGPOINT(0, 0), ST_GEOGPOINT(-30, 0), ST_GEOGPOINT(150, 0) UNION ALL
  SELECT 6 id, ST_GEOGPOINT(0, 0), NULL, NULL UNION ALL
  SELECT 7 id, NULL, ST_GEOGPOINT(0, 0), NULL UNION ALL
  SELECT 8 id, NULL, NULL, ST_GEOGPOINT(0, 0))
SELECT ST_ANGLE(geo1,geo2,geo3) AS angle FROM geos ORDER BY id;

/*---------------------*
 | angle               |
 +---------------------+
 | 4.71238898038469    |
 | 0.78547432161873854 |
 | 0                   |
 | NULL                |
 | NULL                |
 | NULL                |
 | NULL                |
 | NULL                |
 *---------------------*/

ST_AREA

ST_AREA(geography_expression[, use_spheroid])

Description

Returns the area in square meters covered by the polygons in the input GEOGRAPHY.

If geography_expression is a point or a line, returns zero. If geography_expression is a collection, returns the area of the polygons in the collection; if the collection does not contain polygons, returns zero.

The optional use_spheroid parameter determines how this function measures distance. If use_spheroid is FALSE, the function measures distance on the surface of a perfect sphere.

The use_spheroid parameter currently only supports the value FALSE. The default value of use_spheroid is FALSE.

Return type

FLOAT64

ST_ASBINARY

ST_ASBINARY(geography_expression)

Description

Returns the WKB representation of an input GEOGRAPHY.

See ST_GEOGFROMWKB to construct a GEOGRAPHY from WKB.

Return type

BYTES

ST_ASGEOJSON

ST_ASGEOJSON(geography_expression)

Description

Returns the RFC 7946 compliant GeoJSON representation of the input GEOGRAPHY.

A GoogleSQL GEOGRAPHY has spherical geodesic edges, whereas a GeoJSON Geometry object explicitly has planar edges. To convert between these two types of edges, GoogleSQL adds additional points to the line where necessary so that the resulting sequence of edges remains within 10 meters of the original edge.

See ST_GEOGFROMGEOJSON to construct a GEOGRAPHY from GeoJSON.

Return type

STRING

ST_ASTEXT

ST_ASTEXT(geography_expression)

Description

Returns the WKT representation of an input GEOGRAPHY.

See ST_GEOGFROMTEXT to construct a GEOGRAPHY from WKT.

Return type

STRING

ST_AZIMUTH

ST_AZIMUTH(point_geography_1, point_geography_2)

Description

Takes two point GEOGRAPHY values, and returns the azimuth of the line segment formed by points 1 and 2. The azimuth is the angle in radians measured between the line from point 1 facing true North to the line segment from point 1 to point 2.

The positive angle is measured clockwise on the surface of a sphere. For example, the azimuth for a line segment:

• Pointing North is 0
• Pointing East is PI/2
• Pointing South is PI
• Pointing West is 3PI/2

ST_AZIMUTH has the following edge cases:

• If the two input points are the same, returns NULL.
• If the two input points are exactly antipodal, returns NULL.
• If either of the input geographies are not single points or are the empty geography, throws an error.

Return type

FLOAT64

Example

WITH geos AS (
  SELECT 1 id, ST_GEOGPOINT(1, 0) AS geo1, ST_GEOGPOINT(0, 0) AS geo2 UNION ALL
  SELECT 2, ST_GEOGPOINT(0, 0), ST_GEOGPOINT(1, 0) UNION ALL
  SELECT 3, ST_GEOGPOINT(0, 0), ST_GEOGPOINT(0, 1) UNION ALL
  -- identical
  SELECT 4, ST_GEOGPOINT(0, 0), ST_GEOGPOINT(0, 0) UNION ALL
  -- antipode
  SELECT 5, ST_GEOGPOINT(-30, 0), ST_GEOGPOINT(150, 0) UNION ALL
  -- nulls
  SELECT 6, ST_GEOGPOINT(0, 0), NULL UNION ALL
  SELECT 7, NULL, ST_GEOGPOINT(0, 0))
SELECT ST_AZIMUTH(geo1, geo2) AS azimuth FROM geos ORDER BY id;

/*--------------------*
 | azimuth            |
 +--------------------+
 | 4.71238898038469   |
 | 1.5707963267948966 |
 | 0                  |
 | NULL               |
 | NULL               |
 | NULL               |
 | NULL               |
 *--------------------*/

ST_BOUNDARY

ST_BOUNDARY(geography_expression)

Description

Returns a single GEOGRAPHY that contains the union of the boundaries of each component in the given input GEOGRAPHY.

The boundary of each component of a GEOGRAPHY is defined as follows:

• The boundary of a point is empty.
• The boundary of a linestring consists of the endpoints of the linestring.
• The boundary of a polygon consists of the linestrings that form the polygon shell and each of the polygon's holes.

Return type

GEOGRAPHY

ST_BOUNDINGBOX

ST_BOUNDINGBOX(geography_expression)

Description

Returns a STRUCT that represents the bounding box for the specified geography. The bounding box is the minimal rectangle that encloses the geography. The edges of the rectangle follow constant lines of longitude and latitude.

Caveats:

• Returns NULL if the input is NULL or an empty geography.
• The bounding box might cross the antimeridian if this allows for a smaller rectangle. In this case, the bounding box has one of its longitudinal bounds outside of the [-180, 180] range, so that xmin is smaller than the eastmost value xmax.

Return type

STRUCT<xmin FLOAT64, ymin FLOAT64, xmax FLOAT64, ymax FLOAT64>.

Bounding box parts:

• xmin: The westmost constant longitude line that bounds the rectangle.
• xmax: The eastmost constant longitude line that bounds the rectangle.
• ymin: The minimum constant latitude line that bounds the rectangle.
• ymax: The maximum constant latitude line that bounds the rectangle.

Example

WITH data AS (
  SELECT 1 id, ST_GEOGFROMTEXT('POLYGON((-125 48, -124 46, -117 46, -117 49, -125 48))') g
  UNION ALL
  SELECT 2 id, ST_GEOGFROMTEXT('POLYGON((172 53, -130 55, -141 70, 172 53))') g
  UNION ALL
  SELECT 3 id, ST_GEOGFROMTEXT('POINT EMPTY') g
  UNION ALL
  SELECT 4 id, ST_GEOGFROMTEXT('POLYGON((172 53, -141 70, -130 55, 172 53))', oriented => TRUE)
)
SELECT id, ST_BOUNDINGBOX(g) AS box
FROM data

/*----+------------------------------------------*
 | id | box                                      |
 +----+------------------------------------------+
 | 1  | {xmin:-125, ymin:46, xmax:-117, ymax:49} |
 | 2  | {xmin:172, ymin:53, xmax:230, ymax:70}   |
 | 3  | NULL                                     |
 | 4  | {xmin:-180, ymin:-90, xmax:180, ymax:90} |
 *----+------------------------------------------*/

See ST_EXTENT for the aggregate version of ST_BOUNDINGBOX.

ST_BUFFER

ST_BUFFER(
    geography,
    buffer_radius
    [, num_seg_quarter_circle => num_segments]
    [, use_spheroid => boolean_expression]
    [, endcap => endcap_style]
    [, side => line_side])

Description

Returns a GEOGRAPHY that represents the buffer around the input GEOGRAPHY. This function is similar to ST_BUFFERWITHTOLERANCE, but you specify the number of segments instead of providing tolerance to determine how much the resulting geography can deviate from the ideal buffer radius.

• geography: The input GEOGRAPHY to encircle with the buffer radius.
• buffer_radius: FLOAT64 that represents the radius of the buffer around the input geography. The radius is in meters. Note that polygons contract when buffered with a negative buffer_radius. Polygon shells and holes that are contracted to a point are discarded.
• num_seg_quarter_circle: (Optional) FLOAT64 specifies the number of segments that are used to approximate a quarter circle. The default value is 8.0. Naming this argument is optional.
• endcap: (Optional) STRING allows you to specify one of two endcap styles: ROUND and FLAT. The default value is ROUND. This option only affects the endcaps of buffered linestrings.
• side: (Optional) STRING allows you to specify one of three possibilities for lines: BOTH, LEFT, and RIGHT. The default is BOTH. This option only affects how linestrings are buffered.
• use_spheroid: (Optional) BOOL determines how this function measures distance. If use_spheroid is FALSE, the function measures distance on the surface of a perfect sphere. The use_spheroid parameter currently only supports the value FALSE. The default value of use_spheroid is FALSE.

Return type

Polygon GEOGRAPHY

Example

The following example shows the result of ST_BUFFER on a point. A buffered point is an approximated circle. When num_seg_quarter_circle = 2, there are two line segments in a quarter circle, and therefore the buffered circle has eight sides and ST_NUMPOINTS returns nine vertices. When num_seg_quarter_circle = 8, there are eight line segments in a quarter circle, and therefore the buffered circle has thirty-two sides and ST_NUMPOINTS returns thirty-three vertices.

SELECT
  -- num_seg_quarter_circle=2
  ST_NUMPOINTS(ST_BUFFER(ST_GEOGFROMTEXT('POINT(1 2)'), 50, 2)) AS eight_sides,
  -- num_seg_quarter_circle=8, since 8 is the default
  ST_NUMPOINTS(ST_BUFFER(ST_GEOGFROMTEXT('POINT(100 2)'), 50)) AS thirty_two_sides;

/*-------------+------------------*
 | eight_sides | thirty_two_sides |
 +-------------+------------------+
 | 9           | 33               |
 *-------------+------------------*/

ST_BUFFERWITHTOLERANCE

ST_BUFFERWITHTOLERANCE(
    geography,
    buffer_radius,
    tolerance_meters => tolerance
    [, use_spheroid => boolean_expression]
    [, endcap => endcap_style]
    [, side => line_side])

Returns a GEOGRAPHY that represents the buffer around the input GEOGRAPHY. This function is similar to ST_BUFFER, but you provide tolerance instead of segments to determine how much the resulting geography can deviate from the ideal buffer radius.

• geography: The input GEOGRAPHY to encircle with the buffer radius.
• buffer_radius: FLOAT64 that represents the radius of the buffer around the input geography. The radius is in meters. Note that polygons contract when buffered with a negative buffer_radius. Polygon shells and holes that are contracted to a point are discarded.
• tolerance_meters: FLOAT64 specifies a tolerance in meters with which the shape is approximated. Tolerance determines how much a polygon can deviate from the ideal radius. Naming this argument is optional.
• endcap: (Optional) STRING allows you to specify one of two endcap styles: ROUND and FLAT. The default value is ROUND. This option only affects the endcaps of buffered linestrings.
• side: (Optional) STRING allows you to specify one of three possible line styles: BOTH, LEFT, and RIGHT. The default is BOTH. This option only affects the endcaps of buffered linestrings.
• use_spheroid: (Optional) BOOL determines how this function measures distance. If use_spheroid is FALSE, the function measures distance on the surface of a perfect sphere. The use_spheroid parameter currently only supports the value FALSE. The default value of use_spheroid is FALSE.

Return type

Polygon GEOGRAPHY

Example

The following example shows the results of ST_BUFFERWITHTOLERANCE on a point, given two different values for tolerance but with the same buffer radius of 100. A buffered point is an approximated circle. When tolerance_meters=25, the tolerance is a large percentage of the buffer radius, and therefore only five segments are used to approximate a circle around the input point. When tolerance_meters=1, the tolerance is a much smaller percentage of the buffer radius, and therefore twenty-four edges are used to approximate a circle around the input point.

SELECT
  -- tolerance_meters=25, or 25% of the buffer radius.
  ST_NumPoints(ST_BUFFERWITHTOLERANCE(ST_GEOGFROMTEXT('POINT(1 2)'), 100, 25)) AS five_sides,
  -- tolerance_meters=1, or 1% of the buffer radius.
  st_NumPoints(ST_BUFFERWITHTOLERANCE(ST_GEOGFROMTEXT('POINT(100 2)'), 100, 1)) AS twenty_four_sides;

/*------------+-------------------*
 | five_sides | twenty_four_sides |
 +------------+-------------------+
 | 6          | 24                |
 *------------+-------------------*/

ST_CENTROID

ST_CENTROID(geography_expression)

Description

Returns the centroid of the input GEOGRAPHY as a single point GEOGRAPHY.

The centroid of a GEOGRAPHY is the weighted average of the centroids of the highest-dimensional components in the GEOGRAPHY. The centroid for components in each dimension is defined as follows:

• The centroid of points is the arithmetic mean of the input coordinates.
• The centroid of linestrings is the centroid of all the edges weighted by length. The centroid of each edge is the geodesic midpoint of the edge.
• The centroid of a polygon is its center of mass.

If the input GEOGRAPHY is empty, an empty GEOGRAPHY is returned.

Constraints

In the unlikely event that the centroid of a GEOGRAPHY cannot be defined by a single point on the surface of the Earth, a deterministic but otherwise arbitrary point is returned. This can only happen if the centroid is exactly at the center of the Earth, such as the centroid for a pair of antipodal points, and the likelihood of this happening is vanishingly small.

Return type

Point GEOGRAPHY

ST_CENTROID_AGG

ST_CENTROID_AGG(geography)

Description

Computes the centroid of the set of input GEOGRAPHYs as a single point GEOGRAPHY.

The centroid over the set of input GEOGRAPHYs is the weighted average of the centroid of each individual GEOGRAPHY. Only the GEOGRAPHYs with the highest dimension present in the input contribute to the centroid of the entire set. For example, if the input contains both GEOGRAPHYs with lines and GEOGRAPHYs with only points, ST_CENTROID_AGG returns the weighted average of the GEOGRAPHYs with lines, since a line has more dimensions than a point. In this example, ST_CENTROID_AGG ignores GEOGRAPHYs with only points when calculating the aggregate centroid.

ST_CENTROID_AGG ignores NULL input GEOGRAPHY values.

See ST_CENTROID for the non-aggregate version of ST_CENTROID_AGG and the definition of centroid for an individual GEOGRAPHY value.

Return type

Point GEOGRAPHY

Example

The following queries compute the aggregate centroid over a set of GEOGRAPHY values. The input to the first query contains only points, and therefore each value contribute to the aggregate centroid. Also notice that ST_CENTROID_AGG is not equivalent to calling ST_CENTROID on the result of ST_UNION_AGG; duplicates are removed by the union, unlike ST_CENTROID_AGG. The input to the second query has mixed dimensions, and only values with the highest dimension in the set, the lines, affect the aggregate centroid.

SELECT ST_CENTROID_AGG(points) AS st_centroid_agg,
ST_CENTROID(ST_UNION_AGG(points)) AS centroid_of_union
FROM UNNEST([ST_GEOGPOINT(1, 5),
             ST_GEOGPOINT(1, 2),
             ST_GEOGPOINT(1, -1),
             ST_GEOGPOINT(1, -1)]) points;

/*---------------------------+-------------------*
 | st_centroid_agg           | centroid_of_union |
 +---------------------------+-------------------+
 | POINT(1 1.24961422620969) | POINT(1 2)        |
 *---------------------------+-------------------*/

SELECT ST_CENTROID_AGG(points) AS st_centroid_agg
FROM UNNEST([ST_GEOGPOINT(50, 26),
             ST_GEOGPOINT(34, 33.3),
             ST_GEOGFROMTEXT('LINESTRING(0 -1, 0 1)'),
             ST_GEOGFROMTEXT('LINESTRING(0 1, 0 3)')]) points;

/*-----------------*
 | st_centroid_agg |
 +-----------------+
 | POINT(0 1)      |
 *-----------------*/

ST_CLOSESTPOINT

ST_CLOSESTPOINT(geography_1, geography_2[, use_spheroid])

Description

Returns a GEOGRAPHY containing a point on geography_1 with the smallest possible distance to geography_2. This implies that the distance between the point returned by ST_CLOSESTPOINT and geography_2 is less than or equal to the distance between any other point on geography_1 and geography_2.

If either of the input GEOGRAPHYs is empty, ST_CLOSESTPOINT returns NULL.

The optional use_spheroid parameter determines how this function measures distance. If use_spheroid is FALSE, the function measures distance on the surface of a perfect sphere.

The use_spheroid parameter currently only supports the value FALSE. The default value of use_spheroid is FALSE.

Return type

Point GEOGRAPHY

ST_CLUSTERDBSCAN

ST_CLUSTERDBSCAN(geography_column, epsilon, minimum_geographies)
OVER over_clause

over_clause:
  { named_window | ( [ window_specification ] ) }

window_specification:
  [ named_window ]
  [ PARTITION BY partition_expression [, ...] ]
  [ ORDER BY expression [ { ASC | DESC }  ] [, ...] ]

Performs DBSCAN clustering on a column of geographies. Returns a 0-based cluster number.

To learn more about the OVER clause and how to use it, see Window function calls.

Input parameters

• geography_column: A column of GEOGRAPHYs that is clustered.
• epsilon: The epsilon that specifies the radius, measured in meters, around a core value. Non-negative FLOAT64 value.
• minimum_geographies: Specifies the minimum number of geographies in a single cluster. Only dense input forms a cluster, otherwise it is classified as noise. Non-negative INT64 value.

Geography types and the DBSCAN algorithm

The DBSCAN algorithm identifies high-density clusters of data and marks outliers in low-density areas of noise. Geographies passed in through geography_column are classified in one of three ways by the DBSCAN algorithm:

• Core value: A geography is a core value if it is within epsilon distance of minimum_geographies geographies, including itself. The core value starts a new cluster, or is added to the same cluster as a core value within epsilon distance. Core values are grouped in a cluster together with all other core and border values that are within epsilon distance.
• Border value: A geography is a border value if it is within epsilon distance of a core value. It is added to the same cluster as a core value within epsilon distance. A border value may be within epsilon distance of more than one cluster. In this case, it may be arbitrarily assigned to either cluster and the function will produce the same result in subsequent calls.
• Noise: A geography is noise if it is neither a core nor a border value. Noise values are assigned to a NULL cluster. An empty GEOGRAPHY is always classified as noise.

Constraints

• The argument minimum_geographies is a non-negative INT64and epsilon is a non-negative FLOAT64.
• An empty geography cannot join any cluster.
• Multiple clustering assignments could be possible for a border value. If a geography is a border value, ST_CLUSTERDBSCAN will assign it to an arbitrary valid cluster.

Return type

INT64 for each geography in the geography column.

Examples

This example performs DBSCAN clustering with a radius of 100,000 meters with a minimum_geographies argument of 1. The geographies being analyzed are a mixture of points, lines, and polygons.

WITH Geos as
  (SELECT 1 as row_id, ST_GEOGFROMTEXT('POINT EMPTY') as geo UNION ALL
    SELECT 2, ST_GEOGFROMTEXT('MULTIPOINT(1 1, 2 2, 4 4, 5 2)') UNION ALL
    SELECT 3, ST_GEOGFROMTEXT('POINT(14 15)') UNION ALL
    SELECT 4, ST_GEOGFROMTEXT('LINESTRING(40 1, 42 34, 44 39)') UNION ALL
    SELECT 5, ST_GEOGFROMTEXT('POLYGON((40 2, 40 1, 41 2, 40 2))'))
SELECT row_id, geo, ST_CLUSTERDBSCAN(geo, 1e5, 1) OVER () AS cluster_num FROM
Geos ORDER BY row_id

/*--------+-----------------------------------+-------------*
 | row_id |                geo                | cluster_num |
 +--------+-----------------------------------+-------------+
 | 1      | GEOMETRYCOLLECTION EMPTY          | NULL        |
 | 2      | MULTIPOINT(1 1, 2 2, 5 2, 4 4)    | 0           |
 | 3      | POINT(14 15)                      | 1           |
 | 4      | LINESTRING(40 1, 42 34, 44 39)    | 2           |
 | 5      | POLYGON((40 2, 40 1, 41 2, 40 2)) | 2           |
 *--------+-----------------------------------+-------------*/

ST_CONTAINS

ST_CONTAINS(geography_1, geography_2)

Description

Returns TRUE if no point of geography_2 is outside geography_1, and the interiors intersect; returns FALSE otherwise.

NOTE: A GEOGRAPHY does not contain its own boundary. Compare with ST_COVERS.

Return type

BOOL

Example

The following query tests whether the polygon POLYGON((1 1, 20 1, 10 20, 1 1)) contains each of the three points (0, 0), (1, 1), and (10, 10), which lie on the exterior, the boundary, and the interior of the polygon respectively.

SELECT
  ST_GEOGPOINT(i, i) AS p,
  ST_CONTAINS(ST_GEOGFROMTEXT('POLYGON((1 1, 20 1, 10 20, 1 1))'),
              ST_GEOGPOINT(i, i)) AS `contains`
FROM UNNEST([0, 1, 10]) AS i;

/*--------------+----------*
 | p            | contains |
 +--------------+----------+
 | POINT(0 0)   | FALSE    |
 | POINT(1 1)   | FALSE    |
 | POINT(10 10) | TRUE     |
 *--------------+----------*/

ST_CONVEXHULL

ST_CONVEXHULL(geography_expression)

Description

Returns the convex hull for the input GEOGRAPHY. The convex hull is the smallest convex GEOGRAPHY that covers the input. A GEOGRAPHY is convex if for every pair of points in the GEOGRAPHY, the geodesic edge connecting the points are also contained in the same GEOGRAPHY.

In most cases, the convex hull consists of a single polygon. Notable edge cases include the following:

• The convex hull of a single point is also a point.
• The convex hull of two or more collinear points is a linestring as long as that linestring is convex.
• If the input GEOGRAPHY spans more than a hemisphere, the convex hull is the full globe. This includes any input that contains a pair of antipodal points.
• ST_CONVEXHULL returns NULL if the input is either NULL or the empty GEOGRAPHY.

Return type

GEOGRAPHY

Examples

The convex hull returned by ST_CONVEXHULL can be a point, linestring, or a polygon, depending on the input.

WITH Geographies AS
 (SELECT ST_GEOGFROMTEXT('POINT(1 1)') AS g UNION ALL
  SELECT ST_GEOGFROMTEXT('LINESTRING(1 1, 2 2)') AS g UNION ALL
  SELECT ST_GEOGFROMTEXT('MULTIPOINT(2 11, 4 12, 0 15, 1 9, 1 12)') AS g)
SELECT
  g AS input_geography,
  ST_CONVEXHULL(g) AS convex_hull
FROM Geographies;

/*-----------------------------------------+--------------------------------------------------------*
 |             input_geography             |                      convex_hull                       |
 +-----------------------------------------+--------------------------------------------------------+
 | POINT(1 1)                              | POINT(0.999999999999943 1)                             |
 | LINESTRING(1 1, 2 2)                    | LINESTRING(2 2, 1.49988573656168 1.5000570914792, 1 1) |
 | MULTIPOINT(1 9, 4 12, 2 11, 1 12, 0 15) | POLYGON((1 9, 4 12, 0 15, 1 9))                        |
 *-----------------------------------------+--------------------------------------------------------*/

ST_COVEREDBY

ST_COVEREDBY(geography_1, geography_2)

Description

Returns FALSE if geography_1 or geography_2 is empty. Returns TRUE if no points of geography_1 lie in the exterior of geography_2.

Given two GEOGRAPHYs a and b, ST_COVEREDBY(a, b) returns the same result as ST_COVERS(b, a). Note the opposite order of arguments.

Return type

BOOL

ST_COVERS

ST_COVERS(geography_1, geography_2)

Description

Returns FALSE if geography_1 or geography_2 is empty. Returns TRUE if no points of geography_2 lie in the exterior of geography_1.

Return type

BOOL

Example

The following query tests whether the polygon POLYGON((1 1, 20 1, 10 20, 1 1)) covers each of the three points (0, 0), (1, 1), and (10, 10), which lie on the exterior, the boundary, and the interior of the polygon respectively.

SELECT
  ST_GEOGPOINT(i, i) AS p,
  ST_COVERS(ST_GEOGFROMTEXT('POLYGON((1 1, 20 1, 10 20, 1 1))'),
            ST_GEOGPOINT(i, i)) AS `covers`
FROM UNNEST([0, 1, 10]) AS i;

/*--------------+--------*
 | p            | covers |
 +--------------+--------+
 | POINT(0 0)   | FALSE  |
 | POINT(1 1)   | TRUE   |
 | POINT(10 10) | TRUE   |
 *--------------+--------*/

ST_DIFFERENCE

ST_DIFFERENCE(geography_1, geography_2)

Description

Returns a GEOGRAPHY that represents the point set difference of geography_1 and geography_2. Therefore, the result consists of the part of geography_1 that does not intersect with geography_2.

If geometry_1 is completely contained in geometry_2, then ST_DIFFERENCE returns an empty GEOGRAPHY.

Constraints

The underlying geometric objects that a GoogleSQL GEOGRAPHY represents correspond to a closed point set. Therefore, ST_DIFFERENCE is the closure of the point set difference of geography_1 and geography_2. This implies that if geography_1 and geography_2 intersect, then a portion of the boundary of geography_2 could be in the difference.

Return type

GEOGRAPHY

Example

The following query illustrates the difference between geog1, a larger polygon POLYGON((0 0, 10 0, 10 10, 0 0)) and geog2, a smaller polygon POLYGON((4 2, 6 2, 8 6, 4 2)) that intersects with geog1. The result is geog1 with a hole where geog2 intersects with it.

SELECT
  ST_DIFFERENCE(
      ST_GEOGFROMTEXT('POLYGON((0 0, 10 0, 10 10, 0 0))'),
      ST_GEOGFROMTEXT('POLYGON((4 2, 6 2, 8 6, 4 2))')
  );

/*--------------------------------------------------------*
 | difference_of_geog1_and_geog2                          |
 +--------------------------------------------------------+
 | POLYGON((0 0, 10 0, 10 10, 0 0), (8 6, 6 2, 4 2, 8 6)) |
 *--------------------------------------------------------*/

ST_DIMENSION

ST_DIMENSION(geography_expression)

Description

Returns the dimension of the highest-dimensional element in the input GEOGRAPHY.

The dimension of each possible element is as follows:

• The dimension of a point is 0.
• The dimension of a linestring is 1.
• The dimension of a polygon is 2.

If the input GEOGRAPHY is empty, ST_DIMENSION returns -1.

Return type

INT64

ST_DISJOINT

ST_DISJOINT(geography_1, geography_2)

Description

Returns TRUE if the intersection of geography_1 and geography_2 is empty, that is, no point in geography_1 also appears in geography_2.

ST_DISJOINT is the logical negation of ST_INTERSECTS.

Return type

BOOL

ST_DISTANCE

ST_DISTANCE(geography_1, geography_2[, use_spheroid])

Description

Returns the shortest distance in meters between two non-empty GEOGRAPHYs.

If either of the input GEOGRAPHYs is empty, ST_DISTANCE returns NULL.

The optional use_spheroid parameter determines how this function measures distance. If use_spheroid is FALSE, the function measures distance on the surface of a perfect sphere. If use_spheroid is TRUE, the function measures distance on the surface of the WGS84 spheroid. The default value of use_spheroid is FALSE.

Return type

FLOAT64

ST_DUMP

ST_DUMP(geography[, dimension])

Description

Returns an ARRAY of simple GEOGRAPHYs where each element is a component of the input GEOGRAPHY. A simple GEOGRAPHY consists of a single point, linestring, or polygon. If the input GEOGRAPHY is simple, the result is a single element. When the input GEOGRAPHY is a collection, ST_DUMP returns an ARRAY with one simple GEOGRAPHY for each component in the collection.

If dimension is provided, the function only returns GEOGRAPHYs of the corresponding dimension. A dimension of -1 is equivalent to omitting dimension.

Return Type

ARRAY<GEOGRAPHY>

Examples

The following example shows how ST_DUMP returns the simple geographies within a complex geography.

WITH example AS (
  SELECT ST_GEOGFROMTEXT('POINT(0 0)') AS geography
  UNION ALL
  SELECT ST_GEOGFROMTEXT('MULTIPOINT(0 0, 1 1)') AS geography
  UNION ALL
  SELECT ST_GEOGFROMTEXT('GEOMETRYCOLLECTION(POINT(0 0), LINESTRING(1 2, 2 1))'))
SELECT
  geography AS original_geography,
  ST_DUMP(geography) AS dumped_geographies
FROM example

/*-------------------------------------+------------------------------------*
 |         original_geographies        |      dumped_geographies            |
 +-------------------------------------+------------------------------------+
 | POINT(0 0)                          | [POINT(0 0)]                       |
 | MULTIPOINT(0 0, 1 1)                | [POINT(0 0), POINT(1 1)]           |
 | GEOMETRYCOLLECTION(POINT(0 0),      | [POINT(0 0), LINESTRING(1 2, 2 1)] |
 |   LINESTRING(1 2, 2 1))             |                                    |
 *-------------------------------------+------------------------------------*/

The following example shows how ST_DUMP with the dimension argument only returns simple geographies of the given dimension.

WITH example AS (
  SELECT ST_GEOGFROMTEXT('GEOMETRYCOLLECTION(POINT(0 0), LINESTRING(1 2, 2 1))') AS geography)
SELECT
  geography AS original_geography,
  ST_DUMP(geography, 1) AS dumped_geographies
FROM example

/*-------------------------------------+------------------------------*
 |         original_geographies        |      dumped_geographies      |
 +-------------------------------------+------------------------------+
 | GEOMETRYCOLLECTION(POINT(0 0),      | [LINESTRING(1 2, 2 1)]       |
 |   LINESTRING(1 2, 2 1))             |                              |
 *-------------------------------------+------------------------------*/

ST_DWITHIN

ST_DWITHIN(geography_1, geography_2, distance[, use_spheroid])

Description

Returns TRUE if the distance between at least one point in geography_1 and one point in geography_2 is less than or equal to the distance given by the distance argument; otherwise, returns FALSE. If either input GEOGRAPHY is empty, ST_DWithin returns FALSE. The given distance is in meters on the surface of the Earth.

The optional use_spheroid parameter determines how this function measures distance. If use_spheroid is FALSE, the function measures distance on the surface of a perfect sphere.

The use_spheroid parameter currently only supports the value FALSE. The default value of use_spheroid is FALSE.

Return type

BOOL

ST_ENDPOINT

ST_ENDPOINT(linestring_geography)

Description

Returns the last point of a linestring geography as a point geography. Returns an error if the input is not a linestring or if the input is empty. Use the SAFE prefix to obtain NULL for invalid input instead of an error.

Return Type

Point GEOGRAPHY

Example

SELECT ST_ENDPOINT(ST_GEOGFROMTEXT('LINESTRING(1 1, 2 1, 3 2, 3 3)')) last

/*--------------*
 | last         |
 +--------------+
 | POINT(3 3)   |
 *--------------*/

ST_EQUALS

ST_EQUALS(geography_1, geography_2)

Description

Checks if two GEOGRAPHY values represent the same GEOGRAPHY value. Returns TRUE if the values are the same, otherwise returns FALSE.

Definitions

• geography_1: The first GEOGRAPHY value to compare.
• geography_2: The second GEOGRAPHY value to compare.

Details

As long as they still represent the same geometric structure, two GEOGRAPHY values can be equal even if the ordering of points or vertices differ. This means that one of the following conditions must be true for this function to return TRUE:

• Both ST_COVERS(geography_1, geography_2) and ST_COVERS(geography_2, geography_1) are TRUE.
• Both geography_1 and geography_2 are empty.

ST_EQUALS is not guaranteed to be a transitive function.

Return type

BOOL

ST_EXTENT

ST_EXTENT(geography_expression)

Description

Returns a STRUCT that represents the bounding box for the set of input GEOGRAPHY values. The bounding box is the minimal rectangle that encloses the geography. The edges of the rectangle follow constant lines of longitude and latitude.

Caveats:

• Returns NULL if all the inputs are NULL or empty geographies.
• The bounding box might cross the antimeridian if this allows for a smaller rectangle. In this case, the bounding box has one of its longitudinal bounds outside of the [-180, 180] range, so that xmin is smaller than the eastmost value xmax.
• If the longitude span of the bounding box is larger than or equal to 180 degrees, the function returns the bounding box with the longitude range of [-180, 180].

Return type

STRUCT<xmin FLOAT64, ymin FLOAT64, xmax FLOAT64, ymax FLOAT64>.

Bounding box parts:

• xmin: The westmost constant longitude line that bounds the rectangle.
• xmax: The eastmost constant longitude line that bounds the rectangle.
• ymin: The minimum constant latitude line that bounds the rectangle.
• ymax: The maximum constant latitude line that bounds the rectangle.

Example

WITH data AS (
  SELECT 1 id, ST_GEOGFROMTEXT('POLYGON((-125 48, -124 46, -117 46, -117 49, -125 48))') g
  UNION ALL
  SELECT 2 id, ST_GEOGFROMTEXT('POLYGON((172 53, -130 55, -141 70, 172 53))') g
  UNION ALL
  SELECT 3 id, ST_GEOGFROMTEXT('POINT EMPTY') g
)
SELECT ST_EXTENT(g) AS box
FROM data

/*----------------------------------------------*
 | box                                          |
 +----------------------------------------------+
 | {xmin:172, ymin:46, xmax:243, ymax:70}       |
 *----------------------------------------------*/

ST_BOUNDINGBOX for the non-aggregate version of ST_EXTENT.

ST_EXTERIORRING

ST_EXTERIORRING(polygon_geography)

Description

Returns a linestring geography that corresponds to the outermost ring of a polygon geography.

• If the input geography is a polygon, gets the outermost ring of the polygon geography and returns the corresponding linestring.
• If the input is the full GEOGRAPHY, returns an empty geography.
• Returns an error if the input is not a single polygon.

Use the SAFE prefix to return NULL for invalid input instead of an error.

Return type

• Linestring GEOGRAPHY
• Empty GEOGRAPHY

Examples

WITH geo as
 (SELECT ST_GEOGFROMTEXT('POLYGON((0 0, 1 4, 2 2, 0 0))') AS g UNION ALL
  SELECT ST_GEOGFROMTEXT('''POLYGON((1 1, 1 10, 5 10, 5 1, 1 1),
                                  (2 2, 3 4, 2 4, 2 2))''') as g)
SELECT ST_EXTERIORRING(g) AS ring FROM geo;

/*---------------------------------------*
 | ring                                  |
 +---------------------------------------+
 | LINESTRING(2 2, 1 4, 0 0, 2 2)        |
 | LINESTRING(5 1, 5 10, 1 10, 1 1, 5 1) |
 *---------------------------------------*/

ST_GEOGFROM

ST_GEOGFROM(expression)

Description

Converts an expression for a STRING or BYTES value into a GEOGRAPHY value.

If expression represents a STRING value, it must be a valid GEOGRAPHY representation in one of the following formats:

• WKT format. To learn more about this format and the requirements to use it, see ST_GEOGFROMTEXT.
• WKB in hexadecimal text format. To learn more about this format and the requirements to use it, see ST_GEOGFROMWKB.
• GeoJSON format. To learn more about this format and the requirements to use it, see ST_GEOGFROMGEOJSON.

If expression represents a BYTES value, it must be a valid GEOGRAPHY binary expression in WKB format. To learn more about this format and the requirements to use it, see ST_GEOGFROMWKB.

If expression is NULL, the output is NULL.

Return type

GEOGRAPHY

Examples

This takes a WKT-formatted string and returns a GEOGRAPHY polygon:

SELECT ST_GEOGFROM('POLYGON((0 0, 0 2, 2 2, 2 0, 0 0))') AS WKT_format;

/*------------------------------------*
 | WKT_format                         |
 +------------------------------------+
 | POLYGON((2 0, 2 2, 0 2, 0 0, 2 0)) |
 *------------------------------------*/

This takes a WKB-formatted hexadecimal-encoded string and returns a GEOGRAPHY point:

SELECT ST_GEOGFROM(FROM_HEX('010100000000000000000000400000000000001040')) AS WKB_format;

/*----------------*
 | WKB_format     |
 +----------------+
 | POINT(2 4)     |
 *----------------*/

This takes WKB-formatted bytes and returns a GEOGRAPHY point:

SELECT ST_GEOGFROM('010100000000000000000000400000000000001040') AS WKB_format;

/*----------------*
 | WKB_format     |
 +----------------+
 | POINT(2 4)     |
 *----------------*/

This takes a GeoJSON-formatted string and returns a GEOGRAPHY polygon:

SELECT ST_GEOGFROM(
  '{ "type": "Polygon", "coordinates": [ [ [2, 0], [2, 2], [1, 2], [0, 2], [0, 0], [2, 0] ] ] }'
) AS GEOJSON_format;

/*-----------------------------------------*
 | GEOJSON_format                          |
 +-----------------------------------------+
 | POLYGON((2 0, 2 2, 1 2, 0 2, 0 0, 2 0)) |
 *-----------------------------------------*/

ST_GEOGFROMGEOJSON

ST_GEOGFROMGEOJSON(
  geojson_string
  [, make_valid => constant_expression ]
)

Description

Returns a GEOGRAPHY value that corresponds to the input GeoJSON representation.

ST_GEOGFROMGEOJSON accepts input that is RFC 7946 compliant.

If the named argument make_valid is set to TRUE, the function attempts to repair polygons that don't conform to Open Geospatial Consortium semantics.

A GoogleSQL GEOGRAPHY has spherical geodesic edges, whereas a GeoJSON Geometry object explicitly has planar edges. To convert between these two types of edges, GoogleSQL adds additional points to the line where necessary so that the resulting sequence of edges remains within 10 meters of the original edge.

See ST_ASGEOJSON to format a GEOGRAPHY as GeoJSON.

Constraints

The JSON input is subject to the following constraints:

• ST_GEOGFROMGEOJSON only accepts JSON geometry fragments and cannot be used to ingest a whole JSON document.
• The input JSON fragment must consist of a GeoJSON geometry type, which includes Point, MultiPoint, LineString, MultiLineString, Polygon, MultiPolygon, and GeometryCollection. Any other GeoJSON type such as Feature or FeatureCollection will result in an error.
• A position in the coordinates member of a GeoJSON geometry type must consist of exactly two elements. The first is the longitude and the second is the latitude. Therefore, ST_GEOGFROMGEOJSON does not support the optional third element for a position in the coordinates member.

Return type

GEOGRAPHY

ST_GEOGFROMTEXT

ST_GEOGFROMTEXT(
  wkt_string
  [ , oriented => value ]
  [ , planar => value ]
  [ , make_valid => value ]
)

Description

Converts a STRING WKT geometry value into a GEOGRAPHY value.

To format GEOGRAPHY value as WKT, use ST_ASTEXT.

Definitions

• wkt_string: A STRING value that contains the WKT format.

• oriented: A named argument with a BOOL literal.

  • If the value is TRUE, any polygons in the input are assumed to be oriented as follows: when traveling along the boundary of the polygon in the order of the input vertices, the interior of the polygon is on the left. This allows WKT to represent polygons larger than a hemisphere. See also ST_MAKEPOLYGONORIENTED, which is similar to ST_GEOGFROMTEXT with oriented=TRUE.

  • If the value is FALSE or omitted, this function returns the polygon with the smaller area.

• planar: A named argument with a BOOL literal. If the value is TRUE, the edges of the linestrings and polygons are assumed to use planar map semantics, rather than GoogleSQL default spherical geodesics semantics. For more information about the differences between spherical geodesics and planar lines, see Coordinate systems and edges.

• make_valid: A named argument with a BOOL literal. If the value is TRUE, the function attempts to repair polygons that don't conform to Open Geospatial Consortium semantics.

Details

• The function does not support three-dimensional geometries that have a Z suffix, nor does it support linear referencing system geometries with an M suffix.
• oriented and planar can't be TRUE at the same time.
• oriented and make_valid can't be TRUE at the same time.

Example

The following query reads the WKT string POLYGON((0 0, 0 2, 2 2, 0 2, 0 0)) both as a non-oriented polygon and as an oriented polygon, and checks whether each result contains the point (1, 1).

WITH polygon AS (SELECT 'POLYGON((0 0, 0 2, 2 2, 2 0, 0 0))' AS p)
SELECT
  ST_CONTAINS(ST_GEOGFROMTEXT(p), ST_GEOGPOINT(1, 1)) AS fromtext_default,
  ST_CONTAINS(ST_GEOGFROMTEXT(p, oriented => FALSE), ST_GEOGPOINT(1, 1)) AS non_oriented,
  ST_CONTAINS(ST_GEOGFROMTEXT(p, oriented => TRUE),  ST_GEOGPOINT(1, 1)) AS oriented
FROM polygon;

/*-------------------+---------------+-----------*
 | fromtext_default  | non_oriented  | oriented  |
 +-------------------+---------------+-----------+
 | TRUE              | TRUE          | FALSE     |
 *-------------------+---------------+-----------*/

The following query converts a WKT string with an invalid polygon to GEOGRAPHY. The WKT string violates two properties of a valid polygon - the loop describing the polygon is not closed, and it contains self-intersection. With the make_valid option, ST_GEOGFROMTEXT successfully converts it to a multipolygon shape.

WITH data AS (
  SELECT 'POLYGON((0 -1, 2 1, 2 -1, 0 1))' wkt)
SELECT
  SAFE.ST_GEOGFROMTEXT(wkt) as geom,
  SAFE.ST_GEOGFROMTEXT(wkt, make_valid => TRUE) as valid_geom
FROM data

/*------+-----------------------------------------------------------------*
 | geom | valid_geom                                                      |
 +------+-----------------------------------------------------------------+
 | NULL | MULTIPOLYGON(((0 -1, 1 0, 0 1, 0 -1)), ((1 0, 2 -1, 2 1, 1 0))) |
 *------+-----------------------------------------------------------------*/

ST_GEOGFROMWKB

ST_GEOGFROMWKB(
  wkb_bytes_expression
  [ , oriented => value ]
  [ , planar => value ]
  [ , make_valid => value ]
)

ST_GEOGFROMWKB(
  wkb_hex_string_expression
  [, oriented => value ]
  [, planar => value ]
  [, make_valid => value ]
)

Description

Converts an expression from a hexadecimal-text STRING or BYTES value into a GEOGRAPHY value. The expression must be in WKB format.

To format GEOGRAPHY as WKB, use ST_ASBINARY.

Definitions

• wkb_bytes_expression: A BYTES value that contains the WKB format.
• wkb_hex_string_expression: A STRING value that contains the hexadecimal-encoded WKB format.

• oriented: A named argument with a BOOL literal.

  • If the value is TRUE, any polygons in the input are assumed to be oriented as follows: when traveling along the boundary of the polygon in the order of the input vertices, the interior of the polygon is on the left. This allows WKB to represent polygons larger than a hemisphere. See also ST_MAKEPOLYGONORIENTED, which is similar to ST_GEOGFROMWKB with oriented=TRUE.

  • If the value is FALSE or omitted, this function returns the polygon with the smaller area.

• planar: A named argument with a BOOL literal. If the value is TRUE, the edges of the linestrings and polygons are assumed to use planar map semantics, rather than GoogleSQL default spherical geodesics semantics. For more information about the differences between spherical geodesics and planar lines, see Coordinate systems and edges.

• make_valid: A named argument with a BOOL literal. If the value is TRUE, the function attempts to repair polygons that don't conform to Open Geospatial Consortium semantics.

Details

• The function does not support three-dimensional geometries that have a Z suffix, nor does it support linear referencing system geometries with an M suffix.
• oriented and planar can't be TRUE at the same time.
• oriented and make_valid can't be TRUE at the same time.

Return type

GEOGRAPHY

Example

The following query reads the hex-encoded WKB data containing LINESTRING(1 1, 3 2) and uses it with planar and geodesic semantics. When planar is used, the function approximates the planar input line using line that contains a chain of geodesic segments.

WITH wkb_data AS (
  SELECT '010200000002000000feffffffffffef3f000000000000f03f01000000000008400000000000000040' geo
)
SELECT
  ST_GeogFromWkb(geo, planar=>TRUE) AS from_planar,
  ST_GeogFromWkb(geo, planar=>FALSE) AS from_geodesic,
FROM wkb_data

/*---------------------------------------+----------------------*
 | from_planar                           | from_geodesic        |
 +---------------------------------------+----------------------+
 | LINESTRING(1 1, 2 1.5, 2.5 1.75, 3 2) | LINESTRING(1 1, 3 2) |
 *---------------------------------------+----------------------*/

ST_GEOGPOINT

ST_GEOGPOINT(longitude, latitude)

Description

Creates a GEOGRAPHY with a single point. ST_GEOGPOINT creates a point from the specified FLOAT64 longitude (in degrees, negative west of the Prime Meridian, positive east) and latitude (in degrees, positive north of the Equator, negative south) parameters and returns that point in a GEOGRAPHY value.

NOTE: Some systems present latitude first; take care with argument order.

Constraints

• Longitudes outside the range [-180, 180] are allowed; ST_GEOGPOINT uses the input longitude modulo 360 to obtain a longitude within [-180, 180].
• Latitudes must be in the range [-90, 90]. Latitudes outside this range will result in an error.

Return type

Point GEOGRAPHY

ST_GEOGPOINTFROMGEOHASH

ST_GEOGPOINTFROMGEOHASH(geohash)

Description

Returns a GEOGRAPHY value that corresponds to a point in the middle of a bounding box defined in the GeoHash.

Return type

Point GEOGRAPHY

ST_GEOHASH

ST_GEOHASH(geography_expression[, maxchars])

Description

Takes a single-point GEOGRAPHY and returns a GeoHash representation of that GEOGRAPHY object.

• geography_expression: Represents a GEOGRAPHY object. Only a GEOGRAPHY object that represents a single point is supported. If ST_GEOHASH is used over an empty GEOGRAPHY object, returns NULL.
• maxchars: This optional INT64 parameter specifies the maximum number of characters the hash will contain. Fewer characters corresponds to lower precision (or, described differently, to a bigger bounding box). maxchars defaults to 20 if not explicitly specified. A valid maxchars value is 1 to 20. Any value below or above is considered unspecified and the default of 20 is used.

Return type

STRING

Example

Returns a GeoHash of the Seattle Center with 10 characters of precision.

SELECT ST_GEOHASH(ST_GEOGPOINT(-122.35, 47.62), 10) geohash

/*--------------*
 | geohash      |
 +--------------+
 | c22yzugqw7   |
 *--------------*/

ST_GEOMETRYTYPE

ST_GEOMETRYTYPE(geography_expression)

Description

Returns the Open Geospatial Consortium (OGC) geometry type that describes the input GEOGRAPHY. The OGC geometry type matches the types that are used in WKT and GeoJSON formats and printed for ST_ASTEXT and ST_ASGEOJSON. ST_GEOMETRYTYPE returns the OGC geometry type with the "ST_" prefix.

ST_GEOMETRYTYPE returns the following given the type on the input:

• Single point geography: Returns ST_Point.
• Collection of only points: Returns ST_MultiPoint.
• Single linestring geography: Returns ST_LineString.
• Collection of only linestrings: Returns ST_MultiLineString.
• Single polygon geography: Returns ST_Polygon.
• Collection of only polygons: Returns ST_MultiPolygon.
• Collection with elements of different dimensions, or the input is the empty geography: Returns ST_GeometryCollection.

Return type

STRING

Example

The following example shows how ST_GEOMETRYTYPE takes geographies and returns the names of their OGC geometry types.

WITH example AS(
  SELECT ST_GEOGFROMTEXT('POINT(0 1)') AS geography
  UNION ALL
  SELECT ST_GEOGFROMTEXT('MULTILINESTRING((2 2, 3 4), (5 6, 7 7))')
  UNION ALL
  SELECT ST_GEOGFROMTEXT('GEOMETRYCOLLECTION(MULTIPOINT(-1 2, 0 12), LINESTRING(-2 4, 0 6))')
  UNION ALL
  SELECT ST_GEOGFROMTEXT('GEOMETRYCOLLECTION EMPTY'))
SELECT
  geography AS WKT,
  ST_GEOMETRYTYPE(geography) AS geometry_type_name
FROM example;

/*-------------------------------------------------------------------+-----------------------*
 | WKT                                                               | geometry_type_name    |
 +-------------------------------------------------------------------+-----------------------+
 | POINT(0 1)                                                        | ST_Point              |
 | MULTILINESTRING((2 2, 3 4), (5 6, 7 7))                           | ST_MultiLineString    |
 | GEOMETRYCOLLECTION(MULTIPOINT(-1 2, 0 12), LINESTRING(-2 4, 0 6)) | ST_GeometryCollection |
 | GEOMETRYCOLLECTION EMPTY                                          | ST_GeometryCollection |
 *-------------------------------------------------------------------+-----------------------*/

ST_HAUSDORFFDISTANCE

ST_HAUSDORFFDISTANCE(
  geography_1,
  geography_2
  [, directed => { TRUE | FALSE } ]
)

Description

Gets the discrete Hausdorff distance, which is the greatest of all the distances from a discrete point in one geography to the closest discrete point in another geography.

Definitions

• geography_1: A GEOGRAPHY value that represents the first geography.
• geography_2: A GEOGRAPHY value that represents the second geography.

• directed: A named argument with a BOOL value. Represents the type of computation to use on the input geographies. If this argument isn't specified, directed => FALSE is used by default.

  • FALSE: The largest Hausdorff distance found in (geography_1, geography_2) and (geography_2, geography_1).

  • TRUE (default): The Hausdorff distance for (geography_1, geography_2).

Details

If an input geography is NULL, the function returns NULL.

Return type

FLOAT64

Example

The following query gets the Hausdorff distance between geo1 and geo2:

WITH data AS (
  SELECT
    ST_GEOGFROMTEXT('LINESTRING(20 70, 70 60, 10 70, 70 70)') AS geo1,
    ST_GEOGFROMTEXT('LINESTRING(20 90, 30 90, 60 10, 90 10)') AS geo2
)
SELECT ST_HAUSDORFFDISTANCE(geo1, geo2, directed=>TRUE) AS distance
FROM data;

/*--------------------+
 | distance           |
 +--------------------+
 | 1688933.9832041925 |
 +--------------------*/

The following query gets the Hausdorff distance between geo2 and geo1:

WITH data AS (
  SELECT
    ST_GEOGFROMTEXT('LINESTRING(20 70, 70 60, 10 70, 70 70)') AS geo1,
    ST_GEOGFROMTEXT('LINESTRING(20 90, 30 90, 60 10, 90 10)') AS geo2
)
SELECT ST_HAUSDORFFDISTANCE(geo2, geo1, directed=>TRUE) AS distance
FROM data;

/*--------------------+
 | distance           |
 +--------------------+
 | 5802892.745488612  |
 +--------------------*/

The following query gets the largest Hausdorff distance between (geo1 and geo2) and (geo2 and geo1):

WITH data AS (
  SELECT
    ST_GEOGFROMTEXT('LINESTRING(20 70, 70 60, 10 70, 70 70)') AS geo1,
    ST_GEOGFROMTEXT('LINESTRING(20 90, 30 90, 60 10, 90 10)') AS geo2
)
SELECT ST_HAUSDORFFDISTANCE(geo1, geo2, directed=>FALSE) AS distance
FROM data;

/*--------------------+
 | distance           |
 +--------------------+
 | 5802892.745488612  |
 +--------------------*/

The following query produces the same results as the previous query because ST_HAUSDORFFDISTANCE uses directed=>FALSE by default.

WITH data AS (
  SELECT
    ST_GEOGFROMTEXT('LINESTRING(20 70, 70 60, 10 70, 70 70)') AS geo1,
    ST_GEOGFROMTEXT('LINESTRING(20 90, 30 90, 60 10, 90 10)') AS geo2
)
SELECT ST_HAUSDORFFDISTANCE(geo1, geo2) AS distance
FROM data;

ST_INTERIORRINGS

ST_INTERIORRINGS(polygon_geography)

Description

Returns an array of linestring geographies that corresponds to the interior rings of a polygon geography. Each interior ring is the border of a hole within the input polygon.

• If the input geography is a polygon, excludes the outermost ring of the polygon geography and returns the linestrings corresponding to the interior rings.
• If the input is the full GEOGRAPHY, returns an empty array.
• If the input polygon has no holes, returns an empty array.
• Returns an error if the input is not a single polygon.

Use the SAFE prefix to return NULL for invalid input instead of an error.

Return type

ARRAY<LineString GEOGRAPHY>

Examples

WITH geo AS (
  SELECT ST_GEOGFROMTEXT('POLYGON((0 0, 1 1, 1 2, 0 0))') AS g UNION ALL
  SELECT ST_GEOGFROMTEXT('POLYGON((1 1, 1 10, 5 10, 5 1, 1 1), (2 2, 3 4, 2 4, 2 2))') UNION ALL
  SELECT ST_GEOGFROMTEXT('POLYGON((1 1, 1 10, 5 10, 5 1, 1 1), (2 2.5, 3.5 3, 2.5 2, 2 2.5), (3.5 7, 4 6, 3 3, 3.5 7))') UNION ALL
  SELECT ST_GEOGFROMTEXT('fullglobe') UNION ALL
  SELECT NULL)
SELECT ST_INTERIORRINGS(g) AS rings FROM geo;

/*----------------------------------------------------------------------------*
 | rings                                                                      |
 +----------------------------------------------------------------------------+
 | []                                                                         |
 | [LINESTRING(2 2, 3 4, 2 4, 2 2)]                                           |
 | [LINESTRING(2.5 2, 3.5 3, 2 2.5, 2.5 2), LINESTRING(3 3, 4 6, 3.5 7, 3 3)] |
 | []                                                                         |
 | NULL                                                                       |
 *----------------------------------------------------------------------------*/

ST_INTERSECTION

ST_INTERSECTION(geography_1, geography_2)

Description

Returns a GEOGRAPHY that represents the point set intersection of the two input GEOGRAPHYs. Thus, every point in the intersection appears in both geography_1 and geography_2.

If the two input GEOGRAPHYs are disjoint, that is, there are no points that appear in both input geometry_1 and geometry_2, then an empty GEOGRAPHY is returned.

See ST_INTERSECTS, ST_DISJOINT for related predicate functions.

Return type

GEOGRAPHY

ST_INTERSECTS

ST_INTERSECTS(geography_1, geography_2)

Description

Returns TRUE if the point set intersection of geography_1 and geography_2 is non-empty. Thus, this function returns TRUE if there is at least one point that appears in both input GEOGRAPHYs.

If ST_INTERSECTS returns TRUE, it implies that ST_DISJOINT returns FALSE.

Return type

BOOL

ST_INTERSECTSBOX

ST_INTERSECTSBOX(geography, lng1, lat1, lng2, lat2)

Description

Returns TRUE if geography intersects the rectangle between [lng1, lng2] and [lat1, lat2]. The edges of the rectangle follow constant lines of longitude and latitude. lng1 and lng2 specify the westmost and eastmost constant longitude lines that bound the rectangle, and lat1 and lat2 specify the minimum and maximum constant latitude lines that bound the rectangle.

Specify all longitude and latitude arguments in degrees.

Constraints

The input arguments are subject to the following constraints:

• Latitudes should be in the [-90, 90] degree range.
• Longitudes should follow either of the following rules:
  • Both longitudes are in the [-180, 180] degree range.
  • One of the longitudes is in the [-180, 180] degree range, and lng2 - lng1 is in the [0, 360] interval.

Return type

BOOL

Example

SELECT p, ST_INTERSECTSBOX(p, -90, 0, 90, 20) AS box1,
       ST_INTERSECTSBOX(p, 90, 0, -90, 20) AS box2
FROM UNNEST([ST_GEOGPOINT(10, 10), ST_GEOGPOINT(170, 10),
             ST_GEOGPOINT(30, 30)]) p

/*----------------+--------------+--------------*
 | p              | box1         | box2         |
 +----------------+--------------+--------------+
 | POINT(10 10)   | TRUE         | FALSE        |
 | POINT(170 10)  | FALSE        | TRUE         |
 | POINT(30 30)   | FALSE        | FALSE        |
 *----------------+--------------+--------------*/

ST_ISCLOSED

ST_ISCLOSED(geography_expression)

Description

Returns TRUE for a non-empty Geography, where each element in the Geography has an empty boundary. The boundary for each element can be defined with ST_BOUNDARY.

• A point is closed.
• A linestring is closed if the start and end points of the linestring are the same.
• A polygon is closed only if it is a full polygon.
• A collection is closed if and only if every element in the collection is closed.

An empty GEOGRAPHY is not closed.

Return type

BOOL

Example

WITH example AS(
  SELECT ST_GEOGFROMTEXT('POINT(5 0)') AS geography
  UNION ALL
  SELECT ST_GEOGFROMTEXT('LINESTRING(0 1, 4 3, 2 6, 0 1)') AS geography
  UNION ALL
  SELECT ST_GEOGFROMTEXT('LINESTRING(2 6, 1 3, 3 9)') AS geography
  UNION ALL
  SELECT ST_GEOGFROMTEXT('GEOMETRYCOLLECTION(POINT(0 0), LINESTRING(1 2, 2 1))') AS geography
  UNION ALL
  SELECT ST_GEOGFROMTEXT('GEOMETRYCOLLECTION EMPTY'))
SELECT
  geography,
  ST_ISCLOSED(geography) AS is_closed,
FROM example;

/*------------------------------------------------------+-----------*
 | geography                                            | is_closed |
 +------------------------------------------------------+-----------+
 | POINT(5 0)                                           | TRUE      |
 | LINESTRING(0 1, 4 3, 2 6, 0 1)                       | TRUE      |
 | LINESTRING(2 6, 1 3, 3 9)                            | FALSE     |
 | GEOMETRYCOLLECTION(POINT(0 0), LINESTRING(1 2, 2 1)) | FALSE     |
 | GEOMETRYCOLLECTION EMPTY                             | FALSE     |
 *------------------------------------------------------+-----------*/

ST_ISCOLLECTION

ST_ISCOLLECTION(geography_expression)

Description

Returns TRUE if the total number of points, linestrings, and polygons is greater than one.

An empty GEOGRAPHY is not a collection.

Return type

BOOL

ST_ISEMPTY

ST_ISEMPTY(geography_expression)

Description

Returns TRUE if the given GEOGRAPHY is empty; that is, the GEOGRAPHY does not contain any points, lines, or polygons.

NOTE: An empty GEOGRAPHY is not associated with a particular geometry shape. For example, the results of expressions ST_GEOGFROMTEXT('POINT EMPTY') and ST_GEOGFROMTEXT('GEOMETRYCOLLECTION EMPTY') are identical.

Return type

BOOL

ST_ISRING

ST_ISRING(geography_expression)

Description

Returns TRUE if the input GEOGRAPHY is a linestring and if the linestring is both ST_ISCLOSED and simple. A linestring is considered simple if it does not pass through the same point twice (with the exception of the start and endpoint, which may overlap to form a ring).

An empty GEOGRAPHY is not a ring.

Return type

BOOL

ST_LENGTH

ST_LENGTH(geography_expression[, use_spheroid])

Description

Returns the total length in meters of the lines in the input GEOGRAPHY.

If geography_expression is a point or a polygon, returns zero. If geography_expression is a collection, returns the length of the lines in the collection; if the collection does not contain lines, returns zero.

The optional use_spheroid parameter determines how this function measures distance. If use_spheroid is FALSE, the function measures distance on the surface of a perfect sphere.

The use_spheroid parameter currently only supports the value FALSE. The default value of use_spheroid is FALSE.

Return type

FLOAT64

ST_LINEINTERPOLATEPOINT

ST_LINEINTERPOLATEPOINT(linestring_geography, fraction)

Description

Gets a point at a specific fraction in a linestring GEOGRAPHY value.

Definitions

• linestring_geography: A linestring GEOGRAPHY on which the target point is located.
• fraction: A FLOAT64 value that represents a fraction along the linestring GEOGRAPHY where the target point is located. This should be an inclusive value between 0 (start of the linestring) and 1 (end of the linestring).

Details

• Returns NULL if any input argument is NULL.
• Returns an empty geography if linestring_geography is an empty geography.
• Returns an error if linestring_geography is not a linestring or an empty geography, or if fraction is outside the [0, 1] range.

Return Type

GEOGRAPHY

Example

The following query returns a few points on a linestring. Notice that the midpoint of the linestring LINESTRING(1 1, 5 5) is slightly different from POINT(3 3) because the GEOGRAPHY type uses geodesic line segments.

WITH fractions AS (
    SELECT 0 AS fraction UNION ALL
    SELECT 0.5 UNION ALL
    SELECT 1 UNION ALL
    SELECT NULL
  )
SELECT
  fraction,
  ST_LINEINTERPOLATEPOINT(ST_GEOGFROMTEXT('LINESTRING(1 1, 5 5)'), fraction)
    AS point
FROM fractions

/*-------------+-------------------------------------------*
 | fraction    | point                                     |
 +-------------+-------------------------------------------+
 | 0           | POINT(1 1)                                |
 | 0.5         | POINT(2.99633827268976 3.00182528336078)  |
 | 1           | POINT(5 5)                                |
 | NULL        | NULL                                      |
 *-------------+-------------------------------------------*/

ST_LINELOCATEPOINT

ST_LINELOCATEPOINT(linestring_geography, point_geography)

Description

Gets a section of a linestring between the start point and a selected point (a point on the linestring closest to the point_geography argument). Returns the percentage that this section represents in the linestring.

Details:

• To select a point on the linestring GEOGRAPHY (linestring_geography), this function takes a point GEOGRAPHY (point_geography) and finds the closest point to it on the linestring.
• If two points on linestring_geography are an equal distance away from point_geography, it is not guaranteed which one will be selected.
• The return value is an inclusive value between 0 and 1 (0-100%).
• If the selected point is the start point on the linestring, function returns 0 (0%).
• If the selected point is the end point on the linestring, function returns 1 (100%).

NULL and error handling:

• Returns NULL if any input argument is NULL.
• Returns an error if linestring_geography is not a linestring or if point_geography is not a point. Use the SAFE prefix to obtain NULL for invalid input instead of an error.

Return Type

FLOAT64

Examples

WITH geos AS (
    SELECT ST_GEOGPOINT(0, 0) AS point UNION ALL
    SELECT ST_GEOGPOINT(1, 0) UNION ALL
    SELECT ST_GEOGPOINT(1, 1) UNION ALL
    SELECT ST_GEOGPOINT(2, 2) UNION ALL
    SELECT ST_GEOGPOINT(3, 3) UNION ALL
    SELECT ST_GEOGPOINT(4, 4) UNION ALL
    SELECT ST_GEOGPOINT(5, 5) UNION ALL
    SELECT ST_GEOGPOINT(6, 5) UNION ALL
    SELECT NULL
  )
SELECT
  point AS input_point,
  ST_LINELOCATEPOINT(ST_GEOGFROMTEXT('LINESTRING(1 1, 5 5)'), point)
    AS percentage_from_beginning
FROM geos

/*-------------+---------------------------*
 | input_point | percentage_from_beginning |
 +-------------+---------------------------+
 | POINT(0 0)  | 0                         |
 | POINT(1 0)  | 0                         |
 | POINT(1 1)  | 0                         |
 | POINT(2 2)  | 0.25015214685147907       |
 | POINT(3 3)  | 0.5002284283637185        |
 | POINT(4 4)  | 0.7501905913884388        |
 | POINT(5 5)  | 1                         |
 | POINT(6 5)  | 1                         |
 | NULL        | NULL                      |
 *-------------+---------------------------*/

ST_LINESUBSTRING

ST_LINESUBSTRING(linestring_geography, start_fraction, end_fraction);

Description

Gets a segment of a linestring at a specific starting and ending fraction.

Definitions

• linestring_geography: The LineString GEOGRAPHY value that represents the linestring from which to extract a segment.
• start_fraction: FLOAT64 value that represents the starting fraction of the total length of linestring_geography. This must be an inclusive value between 0 and 1 (0-100%).
• end_fraction: FLOAT64 value that represents the ending fraction of the total length of linestring_geography. This must be an inclusive value between 0 and 1 (0-100%).

Details

end_fraction must be greater than or equal to start_fraction.

If start_fraction and end_fraction are equal, a linestring with only one point is produced.

Return type

• LineString GEOGRAPHY if the resulting geography has more than one point.
• Point GEOGRAPHY if the resulting geography has only one point.

Example

The following query returns the second half of the linestring:

WITH data AS (
  SELECT ST_GEOGFROMTEXT('LINESTRING(20 70, 70 60, 10 70, 70 70)') AS geo1
)
SELECT ST_LINESUBSTRING(geo1, 0.5, 1) AS segment
FROM data;

/*-------------------------------------------------------------+
 | segment                                                     |
 +-------------------------------------------------------------+
 | LINESTRING(49.4760661523471 67.2419539103851, 10 70, 70 70) |
 +-------------------------------------------------------------*/

The following query returns a linestring that only contains one point:

WITH data AS (
  SELECT ST_GEOGFROMTEXT('LINESTRING(20 70, 70 60, 10 70, 70 70)') AS geo1
)
SELECT ST_LINESUBSTRING(geo1, 0.5, 0.5) AS segment
FROM data;

/*------------------------------------------+
 | segment                                  |
 +------------------------------------------+
 | POINT(49.4760661523471 67.2419539103851) |
 +------------------------------------------*/

ST_MAKELINE

ST_MAKELINE(geography_1, geography_2)

ST_MAKELINE(array_of_geography)

Description

Creates a GEOGRAPHY with a single linestring by concatenating the point or line vertices of each of the input GEOGRAPHYs in the order they are given.

ST_MAKELINE comes in two variants. For the first variant, input must be two GEOGRAPHYs. For the second, input must be an ARRAY of type GEOGRAPHY. In either variant, each input GEOGRAPHY must consist of one of the following values:

• Exactly one point.
• Exactly one linestring.

For the first variant of ST_MAKELINE, if either input GEOGRAPHY is NULL, ST_MAKELINE returns NULL. For the second variant, if input ARRAY or any element in the input ARRAY is NULL, ST_MAKELINE returns NULL.

Constraints

Every edge must span strictly less than 180 degrees.

NOTE: The GoogleSQL snapping process may discard sufficiently short edges and snap the two endpoints together. For instance, if two input GEOGRAPHYs each contain a point and the two points are separated by a distance less than the snap radius, the points will be snapped together. In such a case the result will be a GEOGRAPHY with exactly one point.

Return type

LineString GEOGRAPHY

ST_MAKEPOLYGON

ST_MAKEPOLYGON(polygon_shell[, array_of_polygon_holes])

Description

Creates a GEOGRAPHY containing a single polygon from linestring inputs, where each input linestring is used to construct a polygon ring.

ST_MAKEPOLYGON comes in two variants. For the first variant, the input linestring is provided by a single GEOGRAPHY containing exactly one linestring. For the second variant, the input consists of a single GEOGRAPHY and an array of GEOGRAPHYs, each containing exactly one linestring.

The first GEOGRAPHY in either variant is used to construct the polygon shell. Additional GEOGRAPHYs provided in the input ARRAY specify a polygon hole. For every input GEOGRAPHY containing exactly one linestring, the following must be true:

• The linestring must consist of at least three distinct vertices.
• The linestring must be closed: that is, the first and last vertex have to be the same. If the first and last vertex differ, the function constructs a final edge from the first vertex to the last.

For the first variant of ST_MAKEPOLYGON, if either input GEOGRAPHY is NULL, ST_MAKEPOLYGON returns NULL. For the second variant, if input ARRAY or any element in the ARRAY is NULL, ST_MAKEPOLYGON returns NULL.

NOTE: ST_MAKEPOLYGON accepts an empty GEOGRAPHY as input. ST_MAKEPOLYGON interprets an empty GEOGRAPHY as having an empty linestring, which will create a full loop: that is, a polygon that covers the entire Earth.

Constraints

Together, the input rings must form a valid polygon:

• The polygon shell must cover each of the polygon holes.
• There can be only one polygon shell (which has to be the first input ring). This implies that polygon holes cannot be nested.
• Polygon rings may only intersect in a vertex on the boundary of both rings.

Every edge must span strictly less than 180 degrees.

Each polygon ring divides the sphere into two regions. The first input linesting to ST_MAKEPOLYGON forms the polygon shell, and the interior is chosen to be the smaller of the two regions. Each subsequent input linestring specifies a polygon hole, so the interior of the polygon is already well-defined. In order to define a polygon shell such that the interior of the polygon is the larger of the two regions, see ST_MAKEPOLYGONORIENTED.

NOTE: The GoogleSQL snapping process may discard sufficiently short edges and snap the two endpoints together. Hence, when vertices are snapped together, it is possible that a polygon hole that is sufficiently small may disappear, or the output GEOGRAPHY may contain only a line or a point.

Return type

GEOGRAPHY

ST_MAKEPOLYGONORIENTED

ST_MAKEPOLYGONORIENTED(array_of_geography)

Description

Like ST_MAKEPOLYGON, but the vertex ordering of each input linestring determines the orientation of each polygon ring. The orientation of a polygon ring defines the interior of the polygon as follows: if someone walks along the boundary of the polygon in the order of the input vertices, the interior of the polygon is on the left. This applies for each polygon ring provided.

This variant of the polygon constructor is more flexible since ST_MAKEPOLYGONORIENTED can construct a polygon such that the interior is on either side of the polygon ring. However, proper orientation of polygon rings is critical in order to construct the desired polygon.

If the input ARRAY or any element in the ARRAY is NULL, ST_MAKEPOLYGONORIENTED returns NULL.

NOTE: The input argument for ST_MAKEPOLYGONORIENTED may contain an empty GEOGRAPHY. ST_MAKEPOLYGONORIENTED interprets an empty GEOGRAPHY as having an empty linestring, which will create a full loop: that is, a polygon that covers the entire Earth.

Constraints

Together, the input rings must form a valid polygon:

• The polygon shell must cover each of the polygon holes.
• There must be only one polygon shell, which must to be the first input ring. This implies that polygon holes cannot be nested.
• Polygon rings may only intersect in a vertex on the boundary of both rings.

Every edge must span strictly less than 180 degrees.

ST_MAKEPOLYGONORIENTED relies on the ordering of the input vertices of each linestring to determine the orientation of the polygon. This applies to the polygon shell and any polygon holes. ST_MAKEPOLYGONORIENTED expects all polygon holes to have the opposite orientation of the shell. See ST_MAKEPOLYGON for an alternate polygon constructor, and other constraints on building a valid polygon.

NOTE: Due to the GoogleSQL snapping process, edges with a sufficiently short length will be discarded and the two endpoints will be snapped to a single point. Therefore, it is possible that vertices in a linestring may be snapped together such that one or more edge disappears. Hence, it is possible that a polygon hole that is sufficiently small may disappear, or the resulting GEOGRAPHY may contain only a line or a point.

Return type

GEOGRAPHY

ST_MAXDISTANCE

ST_MAXDISTANCE(geography_1, geography_2[, use_spheroid])

Returns the longest distance in meters between two non-empty GEOGRAPHYs; that is, the distance between two vertices where the first vertex is in the first GEOGRAPHY, and the second vertex is in the second GEOGRAPHY. If geography_1 and geography_2 are the same GEOGRAPHY, the function returns the distance between the two most distant vertices in that GEOGRAPHY.

If either of the input GEOGRAPHYs is empty, ST_MAXDISTANCE returns NULL.

The optional use_spheroid parameter determines how this function measures distance. If use_spheroid is FALSE, the function measures distance on the surface of a perfect sphere.

The use_spheroid parameter currently only supports the value FALSE. The default value of use_spheroid is FALSE.

Return type

FLOAT64

ST_NPOINTS

ST_NPOINTS(geography_expression)

Description

An alias of ST_NUMPOINTS.

ST_NUMGEOMETRIES

ST_NUMGEOMETRIES(geography_expression)

Description

Returns the number of geometries in the input GEOGRAPHY. For a single point, linestring, or polygon, ST_NUMGEOMETRIES returns 1. For any collection of geometries, ST_NUMGEOMETRIES returns the number of geometries making up the collection. ST_NUMGEOMETRIES returns 0 if the input is the empty GEOGRAPHY.

Return type

INT64

Example

The following example computes ST_NUMGEOMETRIES for a single point geography, two collections, and an empty geography.

WITH example AS(
  SELECT ST_GEOGFROMTEXT('POINT(5 0)') AS geography
  UNION ALL
  SELECT ST_GEOGFROMTEXT('MULTIPOINT(0 1, 4 3, 2 6)') AS geography
  UNION ALL
  SELECT ST_GEOGFROMTEXT('GEOMETRYCOLLECTION(POINT(0 0), LINESTRING(1 2, 2 1))') AS geography
  UNION ALL
  SELECT ST_GEOGFROMTEXT('GEOMETRYCOLLECTION EMPTY'))
SELECT
  geography,
  ST_NUMGEOMETRIES(geography) AS num_geometries,
FROM example;

/*------------------------------------------------------+----------------*
 | geography                                            | num_geometries |
 +------------------------------------------------------+----------------+
 | POINT(5 0)                                           | 1              |
 | MULTIPOINT(0 1, 4 3, 2 6)                            | 3              |
 | GEOMETRYCOLLECTION(POINT(0 0), LINESTRING(1 2, 2 1)) | 2              |
 | GEOMETRYCOLLECTION EMPTY                             | 0              |
 *------------------------------------------------------+----------------*/

ST_NUMPOINTS

ST_NUMPOINTS(geography_expression)

Description

Returns the number of vertices in the input GEOGRAPHY. This includes the number of points, the number of linestring vertices, and the number of polygon vertices.

NOTE: The first and last vertex of a polygon ring are counted as distinct vertices.

Return type

INT64

ST_PERIMETER

ST_PERIMETER(geography_expression[, use_spheroid])

Description

Returns the length in meters of the boundary of the polygons in the input GEOGRAPHY.

If geography_expression is a point or a line, returns zero. If geography_expression is a collection, returns the perimeter of the polygons in the collection; if the collection does not contain polygons, returns zero.

The optional use_spheroid parameter determines how this function measures distance. If use_spheroid is FALSE, the function measures distance on the surface of a perfect sphere.

The use_spheroid parameter currently only supports the value FALSE. The default value of use_spheroid is FALSE.

Return type

FLOAT64

ST_POINTN

ST_POINTN(linestring_geography, index)

Description

Returns the Nth point of a linestring geography as a point geography, where N is the index. The index is 1-based. Negative values are counted backwards from the end of the linestring, so that -1 is the last point. Returns an error if the input is not a linestring, if the input is empty, or if there is no vertex at the given index. Use the SAFE prefix to obtain NULL for invalid input instead of an error.

Return Type

Point GEOGRAPHY

Example

The following example uses ST_POINTN, ST_STARTPOINT and ST_ENDPOINT to extract points from a linestring.

WITH linestring AS (
    SELECT ST_GEOGFROMTEXT('LINESTRING(1 1, 2 1, 3 2, 3 3)') g
)
SELECT ST_POINTN(g, 1) AS first, ST_POINTN(g, -1) AS last,
    ST_POINTN(g, 2) AS second, ST_POINTN(g, -2) AS second_to_last
FROM linestring;

/*--------------+--------------+--------------+----------------*
 | first        | last         | second       | second_to_last |
 +--------------+--------------+--------------+----------------+
 | POINT(1 1)   | POINT(3 3)   | POINT(2 1)   | POINT(3 2)     |
 *--------------+--------------+--------------+----------------*/

ST_SIMPLIFY

ST_SIMPLIFY(geography, tolerance_meters)

Description

Returns a simplified version of geography, the given input GEOGRAPHY. The input GEOGRAPHY is simplified by replacing nearly straight chains of short edges with a single long edge. The input geography will not change by more than the tolerance specified by tolerance_meters. Thus, simplified edges are guaranteed to pass within tolerance_meters of the original positions of all vertices that were removed from that edge. The given tolerance_meters is in meters on the surface of the Earth.

Note that ST_SIMPLIFY preserves topological relationships, which means that no new crossing edges will be created and the output will be valid. For a large enough tolerance, adjacent shapes may collapse into a single object, or a shape could be simplified to a shape with a smaller dimension.

Constraints

For ST_SIMPLIFY to have any effect, tolerance_meters must be non-zero.

ST_SIMPLIFY returns an error if the tolerance specified by tolerance_meters is one of the following:

• A negative tolerance.
• Greater than ~7800 kilometers.

Return type

GEOGRAPHY

Examples

The following example shows how ST_SIMPLIFY simplifies the input line GEOGRAPHY by removing intermediate vertices.

WITH example AS
 (SELECT ST_GEOGFROMTEXT('LINESTRING(0 0, 0.05 0, 0.1 0, 0.15 0, 2 0)') AS line)
SELECT
   line AS original_line,
   ST_SIMPLIFY(line, 1) AS simplified_line
FROM example;

/*---------------------------------------------+----------------------*
 |                original_line                |   simplified_line    |
 +---------------------------------------------+----------------------+
 | LINESTRING(0 0, 0.05 0, 0.1 0, 0.15 0, 2 0) | LINESTRING(0 0, 2 0) |
 *---------------------------------------------+----------------------*/

The following example illustrates how the result of ST_SIMPLIFY can have a lower dimension than the original shape.

WITH example AS
 (SELECT
    ST_GEOGFROMTEXT('POLYGON((0 0, 0.1 0, 0.1 0.1, 0 0))') AS polygon,
    t AS tolerance
  FROM UNNEST([1000, 10000, 100000]) AS t)
SELECT
  polygon AS original_triangle,
  tolerance AS tolerance_meters,
  ST_SIMPLIFY(polygon, tolerance) AS simplified_result
FROM example

/*-------------------------------------+------------------+-------------------------------------*
 |          original_triangle          | tolerance_meters |          simplified_result          |
 +-------------------------------------+------------------+-------------------------------------+
 | POLYGON((0 0, 0.1 0, 0.1 0.1, 0 0)) |             1000 | POLYGON((0 0, 0.1 0, 0.1 0.1, 0 0)) |
 | POLYGON((0 0, 0.1 0, 0.1 0.1, 0 0)) |            10000 |            LINESTRING(0 0, 0.1 0.1) |
 | POLYGON((0 0, 0.1 0, 0.1 0.1, 0 0)) |           100000 |                          POINT(0 0) |
 *-------------------------------------+------------------+-------------------------------------*/

ST_SNAPTOGRID

ST_SNAPTOGRID(geography_expression, grid_size)

Description

Returns the input GEOGRAPHY, where each vertex has been snapped to a longitude/latitude grid. The grid size is determined by the grid_size parameter which is given in degrees.

Constraints

Arbitrary grid sizes are not supported. The grid_size parameter is rounded so that it is of the form 10^n, where -10 < n < 0.

Return type

GEOGRAPHY

ST_STARTPOINT

ST_STARTPOINT(linestring_geography)

Description

Returns the first point of a linestring geography as a point geography. Returns an error if the input is not a linestring or if the input is empty. Use the SAFE prefix to obtain NULL for invalid input instead of an error.

Return Type

Point GEOGRAPHY

Example

SELECT ST_STARTPOINT(ST_GEOGFROMTEXT('LINESTRING(1 1, 2 1, 3 2, 3 3)')) first

/*--------------*
 | first        |
 +--------------+
 | POINT(1 1)   |
 *--------------*/

ST_TOUCHES

ST_TOUCHES(geography_1, geography_2)

Description

Returns TRUE provided the following two conditions are satisfied:

1. geography_1 intersects geography_2.
2. The interior of geography_1 and the interior of geography_2 are disjoint.

Return type

BOOL

ST_UNION

ST_UNION(geography_1, geography_2)

ST_UNION(array_of_geography)

Description

Returns a GEOGRAPHY that represents the point set union of all input GEOGRAPHYs.

ST_UNION comes in two variants. For the first variant, input must be two GEOGRAPHYs. For the second, the input is an ARRAY of type GEOGRAPHY.

For the first variant of ST_UNION, if an input GEOGRAPHY is NULL, ST_UNION returns NULL. For the second variant, if the input ARRAY value is NULL, ST_UNION returns NULL. For a non-NULL input ARRAY, the union is computed and NULL elements are ignored so that they do not affect the output.

See ST_UNION_AGG for the aggregate version of ST_UNION.

Return type

GEOGRAPHY

Example

SELECT ST_UNION(
  ST_GEOGFROMTEXT('LINESTRING(-122.12 47.67, -122.19 47.69)'),
  ST_GEOGFROMTEXT('LINESTRING(-122.12 47.67, -100.19 47.69)')
) AS results

/*---------------------------------------------------------*
 | results                                                 |
 +---------------------------------------------------------+
 | LINESTRING(-100.19 47.69, -122.12 47.67, -122.19 47.69) |
 *---------------------------------------------------------*/

ST_UNION_AGG

ST_UNION_AGG(geography)

Description

Returns a GEOGRAPHY that represents the point set union of all input GEOGRAPHYs.

ST_UNION_AGG ignores NULL input GEOGRAPHY values.

See ST_UNION for the non-aggregate version of ST_UNION_AGG.

Return type

GEOGRAPHY

Example

SELECT ST_UNION_AGG(items) AS results
FROM UNNEST([
  ST_GEOGFROMTEXT('LINESTRING(-122.12 47.67, -122.19 47.69)'),
  ST_GEOGFROMTEXT('LINESTRING(-122.12 47.67, -100.19 47.69)'),
  ST_GEOGFROMTEXT('LINESTRING(-122.12 47.67, -122.19 47.69)')]) as items;

/*---------------------------------------------------------*
 | results                                                 |
 +---------------------------------------------------------+
 | LINESTRING(-100.19 47.69, -122.12 47.67, -122.19 47.69) |
 *---------------------------------------------------------*/

ST_WITHIN

ST_WITHIN(geography_1, geography_2)

Description

Returns TRUE if no point of geography_1 is outside of geography_2 and the interiors of geography_1 and geography_2 intersect.

Given two geographies a and b, ST_WITHIN(a, b) returns the same result as ST_CONTAINS(b, a). Note the opposite order of arguments.

Return type

BOOL

ST_X

ST_X(point_geography_expression)

Description

Returns the longitude in degrees of the single-point input GEOGRAPHY.

For any input GEOGRAPHY that is not a single point, including an empty GEOGRAPHY, ST_X returns an error. Use the SAFE. prefix to obtain NULL.

Return type

FLOAT64

Example

The following example uses ST_X and ST_Y to extract coordinates from single-point geographies.

WITH points AS
   (SELECT ST_GEOGPOINT(i, i + 1) AS p FROM UNNEST([0, 5, 12]) AS i)
 SELECT
   p,
   ST_X(p) as longitude,
   ST_Y(p) as latitude
FROM points;

/*--------------+-----------+----------*
 | p            | longitude | latitude |
 +--------------+-----------+----------+
 | POINT(0 1)   | 0.0       | 1.0      |
 | POINT(5 6)   | 5.0       | 6.0      |
 | POINT(12 13) | 12.0      | 13.0     |
 *--------------+-----------+----------*/

ST_Y

ST_Y(point_geography_expression)

Description

Returns the latitude in degrees of the single-point input GEOGRAPHY.

For any input GEOGRAPHY that is not a single point, including an empty GEOGRAPHY, ST_Y returns an error. Use the SAFE. prefix to return NULL instead.

Return type

FLOAT64

Example

See ST_X for example usage.