google-polyline

Encodes and decodes Google's polyline format It's a forked version of google-polyline module with minor performance improvements and reversed order of coordinates: longitude, latitude (think x, y or easting, northing), which corresponds to position definition in GeoJSON spec.

Install

$ npm install --save @pirxpilot/google-polyline

# or

$ yarn add @pirxpilot/google-polyline

Usage

const { encode, decode } = require('@pirxpilot/google-polyline')

encode([
  [ -120.2, 38.5 ],
  [ -120.95, 40.7 ],
  [ -126.453, 43.252 ]
])

> '_p~iF~ps|U_ulLnnqC_mqNvxq`@'

decode( '_p~iF~ps|U_ulLnnqC_mqNvxq`@' )

> [
  [ -120.2, 38.5 ],
  [ -120.95, 40.7 ],
  [ -126.453, 43.252 ]
]

API

polyline.encode(points[, options])

returns a string representing encoded polyline

• points is an array of points, each point is a 2 element array [longitude, latitude]
• options.factor - optional (defaults to 1e5), factor by which coordinates are multiplied during encoding
• options.mapFn - can be optionally passed to convert array of elements to [lon. lat] pairs mapFunction is called for each item in points array and has the same signature as Array.map callback
• options.prefix - optional prefix for encoded String

polyline.decode(string[, options ])

returns an array of points representing decoded polyline

• string is an encoded polyline representation
• options.factor - optional (defaults to 1e5), factor by which coordinates are divided after decoding; use factor 1e6 when decoding polylines from OSM data (OSRM, mapzen etc.)
• options.mapFn - optional - if provided it'll be called for each [lon. lat] pair to convert the point before it is added to resulting points array
• start, end - (defaults to 0, points.length) - allows to decode a substring