geographiclib-mgrs

This is a JavaScript port of the MGRS functionality in GeographicLib. It is designed to be a drop in replacement for proj4js mgrs.

Differences between geographiclib-mgrs and proj4js mgrs:

• GeographicLib MGRS supports
  • UTM zones
  • UPS zones
• Proj4js MGRS supports
  • UTM zones

Installation

npm install geographiclib-mgrs --save

Usage

import MGRS from "geographiclib-mgrs";

to convert a MGRS string to a point

const mgrs = "42SUF1230045600";
// optional variable if you want to use the center point or lower left
// default value is false
const centerpoint = false;
const point = MGRS.toPoint(mgrs, centerpoint);
// return [long, lat]

to convert a latlong to a MGRS string

const point = [long, lat];
const accuracy = 5;
const result = MGRS.forward(point, accuracy);
// return MGRS string

to convert a MGRS string to a bounding box

const mgrs = "42SUF123456";
// optional variable if you want to use the center point or lower left
// default value is false
const centerpoint = false;
const point = MGRS.inverse(mgrs);
// return [lowerLeft.lon, lowerLeft.lat, upperRight.lon, upperRight.lat]

It is also possible to access the underlaying geograpiclib functions under MGRS.MGRS and MGRS.UTMUPS, where most methods from geographiclib are aviable.

For example:

MGRS.MGRS.reverse(mgrs, true);
/* returns object
 * zone: UTM zone (zero means UPS).
 * northp: hemisphere (true means north, false means south).
 * x: easting of point (meters).
 * y: northing of point (meters).
 * prec: precision relative to 100 km.
 * */

Verification

The output from this library has been verified against the test data from Geotrans. We use the same verification method as Geotrans and any descipances are because of rounding errors in the input data.

The library is a straight port of GeographicLib from C++ to Javascript and provides the same results as GeographicLib C++.

Licensing

Original GeographicLib by Charles Karney can be found at:

https://geographiclib.sourceforge.io/

It is licensed under the following MIT license:

The MIT License (MIT).

Copyright (c) 2008-2023, Charles Karney

see full license text in GeographicLib source.

Geographiclib-mgrs is licensed under the following MIT license:

MIT License

Copyright (c) 2025 Måns Beckman

see full license text in the LICENSE file