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}.

Options

Option	description	Default
meridian	Latitude of the central meridian	0
latLimit	maximum latitude in degrees < 90	85
standardParallel	longitude of the standard parallel(s)	0

Contributing

If you found a bug, want to propose a feature or feel the urge to complain about your life, feel free to visit the issues page.