Class PolylineCodec

Namespace

LansMap.Core.Vector

Google encoded-polyline (precision 5) decoder, the wire format OSRM and most routing APIs return geometry in.

public static class PolylineCodec

Inheritance

object

PolylineCodec

Remarks

This is a wire boundary: the bytes come from a third-party server and may be corrupt or hostile. Three rules, in order. Nothing throws. Nothing moves a point, so no clamping, because a clamped coordinate is indistinguishable downstream from a real one. What cannot be represented rejects the whole geometry rather than half of it, because a route truncated at the bad point ends in the middle of nowhere with nothing to tell the caller it did. The antimeridian needs no special case: the format encodes differences between absolute coordinates, so a seam-crossing route written as 179.99 then -179.99 lands back in range on its own.

Methods

TryDecode(string, List<LatLon>)

Decodes an encoded polyline into WGS84 coordinates.

public static bool TryDecode(string encoded, List<LatLon> results)

Parameters

encoded string

Encoded polyline body. Null or empty decodes to nothing and succeeds.

results List<LatLon>

Cleared first, then filled. Empty whenever this returns false.

Returns

bool

True when the whole string decoded into coordinates LatLon accepts. False when any latitude leaves -90 to 90, any longitude leaves -180 to 180, or the string ends mid-varint.

Remarks

All or nothing, including for truncation. Deltas accumulate, so a coordinate can leave range with no single delta out of the ordinary: 19 successive +5 degree steps north do it.