| #!/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 |
| # |
| # http://www.apache.org/licenses/LICENSE-2.0 |
| # |
| # Unless required by applicable law or agreed to in writing, software |
| # distributed under the License is distributed on an "AS IS" BASIS, |
| # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| # 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 |
| |
| |
| 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)) |