Source code for

#!/usr/bin/env python
# Copyright 2007 Google Inc.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# See the License for the specific language governing permissions and
# limitations under the License.
"""Utilities to support geo fields on the Python dev server."""

import math

[docs]class LatLng(object): """A class representing a Latitude/Longitude pair.""" _EARTH_RADIUS_METERS = 6371010 def __init__(self, latitude, longitude): """Initializer. Args: latitude: The latitude in degrees. longitude: The longitude in degrees. Raises: TypeError: If a non-numeric latitude or longitude is passed. """ self._lat = latitude self._lng = longitude @property def latitude(self): """Returns the latitude in degrees.""" return self._lat @property def longitude(self): """Returns the longitude in degrees.""" return self._lng def __sub__(self, other): """Subtraction. Args: other: the LatLng which this LatLng is subtracted by. Returns: the great circle distance between two LatLng objects as computed by the Haversine formula. """ assert isinstance(other, LatLng) lat_rad = math.radians(self._lat) lng_rad = math.radians(self._lng) other_lat_rad = math.radians(other.latitude) other_lng_rad = math.radians(other.longitude) dlat = lat_rad - other_lat_rad dlng = lng_rad - other_lng_rad a1 = math.sin(dlat / 2)**2 a2 = math.cos(lat_rad) * math.cos(other_lat_rad) * math.sin(dlng / 2)**2 return 2 * self._EARTH_RADIUS_METERS * math.asin(math.sqrt(a1 + a2))

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