Meziantou.FrameworkEncodedPolyline Class
Encodes and decodes the positions of a line with the encoded polyline algorithm of Google, used by Google Maps, OSRM, Valhalla or Strava, such as _p~iF~ps|U_ulLnnqC_mqNvxq`@.
public static class EncodedPolylineRemarks
The format stores the latitude then the longitude of each position, rounded to a number of decimal digits: 5 for Google Maps and OSRM by default, 6 for Valhalla and the polyline6 geometries of OSRM. It has no altitude: the decoded positions have none, and the altitudes are ignored when encoding.
The coordinates are rounded half away from zero, as the reference implementation, and each position is stored as the difference with the previous rounded position, so the rounding errors do not add up along the line.
Methods
| Name | Description |
|---|---|
| Decode(string, int) | Decodes the positions of an encoded polyline. |
| Encode(IEnumerable<GeoPosition>, int) | Encodes positions as an encoded polyline. |
Decode(string, int)
EncodedPolyline.csDecodes the positions of an encoded polyline.
public static IReadOnlyList<GeoPosition> Decode(string encoded, int precision = 5)Parameters
encodedstring- The encoded polyline.
precisionint- The number of decimal digits of the coordinates: 5 for Google Maps and OSRM, 6 for Valhalla.
Returns
IReadOnlyList<GeoPosition> The positions, without altitude. Create a GeoLineString from them to use them as a geometry.
Exceptions
ArgumentOutOfRangeExceptionprecisionis not between 0 and 10.FormatException- The text is not a valid encoded polyline.
Encode(IEnumerable<GeoPosition>, int)
EncodedPolyline.csEncodes positions as an encoded polyline.
public static string Encode(IEnumerable<GeoPosition> positions, int precision = 5)Parameters
positionsIEnumerable<GeoPosition>- The positions. Their altitudes are ignored.
precisionint- The number of decimal digits of the coordinates: 5 for Google Maps and OSRM, 6 for Valhalla.
Returns
string The encoded polyline.
Exceptions
ArgumentOutOfRangeExceptionprecisionis not between 0 and 10.ArgumentException- A coordinate is not finite or is too large to be encoded.