sphericalmercator

Provides projection math for converting between mercator meters, screen pixels (of 256x256 or configurable-size tiles), and latitude/longitude. Compatible with nodejs packages and in-browser.

See also

• tilebelt provides ZXY tile math utilities in javascript
• mercantile provides similar utilities for projection and tile math in Python

Installation

npm install @mapbox/sphericalmercator

API

Some datatypes are assumed to be arrays: ll is [lon, lat], xy and px are [x, y].

import { SphericalMercator } from '@mapbox/sphericalmercator';

// By default, precomputes up to z30
const merc = new SphericalMercator({
  size: 256,
  antimeridian: true
});

px(ll, zoom)

Convert lon, lat to screen pixel x, y from 0, 0 origin, at a certain zoom level. The inverse of ll. If antimeridian: true is passed on initialization of the SphericalMercator object, this method will support converting longitude values up to 360°.

ll(px, zoom)

Convert screen pixel value to lon, lat, at a certain zoom level. The inverse of px.

bbox(x, y, zoom, tmsStyle, srs)

Convert tile xyz value to bbox of the form [w, s, e, n]

• x {Number} x (longitude) number.
• y {Number} y (latitude) number.
• zoom {Number} zoom.
• tmsStyle {Boolean} whether to compute using tms-style. (optional, default false)
• srs {String} projection for resulting bbox (WGS84|900913). (optional, default WGS84)

Returns bbox array of values in form [w, s, e, n].

xyz(bbox, zoom, tmsStyle, srs)

Convert bbox to xyz bounds

• bbox {Number} bbox in the form [w, s, e, n].
• zoom {Number} zoom.
• tmsStyle {Boolean} whether to compute using tms-style. (optional, default false)
• srs {String} projection of input bbox (WGS84|900913). (optional, default WGS84)

Returns {Object} XYZ bounds containing minX, maxX, minY, maxY properties.

convert(bbox, to)

Convert bbox from 900913 to WGS84 or vice versa

• bbox {Number} bbox in the form [w, s, e, n].
• to {String} projection of resulting bbox (WGS84|900913). (optional, default WGS84)

Returns bbox array of values in form [w, s, e, n].

forward(ll)

Convert lon, lat values to mercator x, y

inverse(xy)

Convert mercator x, y values to lon, lat

Developing

npm ci          # install
npm test        # run tests
npm run format  # format files with prettier