Projections NPM

projections

Collection of (stereographic) map projections. See this Wikipedia list.

Installation

npm install --save projections

Usage

const projections = require('projections') // for all projections
const mercator = require('projections/mercator') // for a specific projection

WGS to map coordinates

const {x, y} = mercator({lon: 13.5, lat: 52.4})
// x ≊ 0.53722
// y ≊ 0.32686

Given an object containing lon and lat, mercator returns an object {x: …, y: …} (0 ≤ x ≤ 1). For details on the range of y, see the map height column in the projections table.

Map coordinates to WGS

const {lon, lat} = mercator({x: 0.53722, y: 0.32686})
// lon ≊ 13.5
// lat ≊ 52.4

Given an object containing x and y (0 ≤ x ≤ 1), mercator returns an object {lon: …, lat: …}.

Be sure to use the same options everytime you're converting coordinates back and forth to get correct results.

Projections

Projection	Full name	Available options	Map height*
`braun`	Braun stereographic	`meridian`, `latLimit`
`central-cylindrical`	Central cylindrical	`meridian`, `latLimit`
`equirectangular`	Equirectangular	`meridian`, `standardParallel`	1 / 2
`gall`	Gall stereographic	`meridian`, `latLimit`
`gall-peters`	Gall–Peters	`meridian`	2 / π
`kavrayskiy-7`	Kavrayskiy VII	`meridian`	1 / √3
`lambert`	Lambert cylindrical equal-area	`meridian`	1 / π
`mercator`	Mercator (Web)	`meridian`, `latLimit`
`miller`	Miller cylindrical	`meridian`, `latLimit`
`sinusoidal`	Sinusoidal	`meridian`	1 / 2
`wagner-6`	Wagner VI	`meridian`	1 / 2

* If the projection uses a latitude limit, the map height is the value of y at {lon: meridian, lat: -latLimit}. Otherwise it is the value of y at {lon: meridian, lat: -90}.