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.project({lon: 13.5, lat: 52.4})
// x ≊ 0.53722
// y ≊ 0.32686

Given an object containing lon and lat, mercator.project 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.inverse({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.