Geodesic calculations

This module defines the Geodesic class which can interface with the Proj geodesic functions. See the Proj geodesic page for more background information.

class cartopy.geodesic.Geodesic(radius=6378137.0, flattening=1 / 298.257223563)

Define an ellipsoid on which to solve geodesic problems.

Parameters

  • radius (float, optional) – Equatorial radius (metres). Defaults to the WGS84 semimajor axis (6378137.0 metres).

  • flattening (float, optional) – Flattening of ellipsoid. Setting flattening = 0 gives a sphere. Negative flattening gives a prolate ellipsoid. If flattening > 1, set flattening to 1/flattening. Defaults to the WGS84 flattening (1/298.257223563).

circle(self, double lon, double lat, double radius, int n_samples=180, endpoint=False)

Find a geodesic circle of given radius at a given point.

Parameters

  • lon (float) – Longitude coordinate of the centre.

  • lat (float) – Latitude coordinate of the centre.

  • radius (float) – The radius of the circle (metres).

  • n_samples (int, optional) – Integer number of sample points of circle.

  • endpoint (bool, optional) – Whether to repeat endpoint at the end of returned array.

Returns

numpy.ndarray, shape=(n_samples, 2) – The evenly spaced longitude-latitude points on the circle.

direct(self, points, azimuths, distances)

Solve the direct geodesic problem where the length of the geodesic is specified in terms of distance.

Can accept and broadcast length 1 arguments. For example, given a single start point and distance, an array of different azimuths can be supplied to locate multiple endpoints.

Parameters

  • points (array_like, shape=(n or 1, 2)) – The starting longitude-latitude point(s) from which to travel.

  • azimuths (float or array_like with shape=(n, )) – List of azimuth values (degrees).

  • distances (float or array_like with shape(n, )) – List of distances values (metres).

Returns

numpy.ndarray, shape=(n, 3) – The longitudes, latitudes, and forward azimuths of the located endpoint(s).

geometry_length(self, geometry)

Return the distance (in physical meters) of the given Shapely geometry.

The geometry is assumed to be in spherical (lon, lat) coordinates.

Parameters

geometry (shapely.geometry.BaseGeometry) – The Shapely geometry to compute the length of. For polygons, the exterior length will be calculated. For multi-part geometries, the sum of the parts will be computed.

inverse(self, points, endpoints)

Solve the inverse geodesic problem.

Can accept and broadcast length 1 arguments. For example, given a single start point, an array of different endpoints can be supplied to find multiple distances.

Parameters

  • points (array_like, shape=(n or 1, 2)) – The starting longitude-latitude point(s) from which to travel.

  • endpoints (array_like, shape=(n or 1, 2)) – The longitude-latitude point(s) to travel to.

Returns

numpy.ndarray, shape=(n, 3) – The distances, and the (forward) azimuths of the start and end points.