Polyline Encode/Decode for Elixir

This is an Elixir implementation of polyline encoding/decoding. Functions are provided to convert a List of {lon, lat} tuples to a String polyline representation and back.

Note: while a lot of libraries use [latitude, longitude] ordering, this library maintains proper cartesian order ({x, y} or {longitude, latitude}) in order to be more interoperable with common formats such as GeoJSON and WKT.

Installation

defp deps do
  [{:polyline, "~> 1.3"}]
end

Usage

Full Documentation

The encode functions accept a precision parameter that defines the number of significant digits to retain when encoding. The same precision must be supplied to the decode or the resulting linestring will be incorrect. The default is 5, which correlates to approximately 1 meter of precision.

Polyline.encode([{-120.2, 38.5}, {-120.95, 40.7}, {-126.453, 43.252}]) #+> "_p~iF~ps|U_ulLnnqC_mqNvxq`@"

Polyline.decode("_p~iF~ps|U_ulLnnqC_mqNvxq`@") #=> [{-120.2, 38.5}, {-120.95, 40.7}, {-126.453, 43.252}]