@zwaarcontrast/ol-graticule-mgrs

Military Grid Reference System (MGRS / NATO grid) for @zwaarcontrast/ol-graticule.

Renders Grid Zone Designators (e.g. 32U) and 100 km squares (e.g. WL) worldwide, with cursor readout of the full MGRS reference. Handles the Norway and Svalbard zone exceptions and falls back to UPS (Universal Polar Stereographic) above 84°N and below 80°S.

Live demo: https://zwaarcontrast.nl/ol-graticule/ol-graticule-mgrs/

Install

npm install \
  @zwaarcontrast/ol-graticule \
  @zwaarcontrast/ol-graticule-projected \
  @zwaarcontrast/ol-graticule-mgrs \
  ol proj4

Peers: ol ^10, proj4 ^2.9, @zwaarcontrast/ol-graticule, @zwaarcontrast/ol-graticule-projected.

Usage

import { UniversalGraticule, CursorPositionControl } from '@zwaarcontrast/ol-graticule';
import { MgrsGridSystem } from '@zwaarcontrast/ol-graticule-mgrs';

const gridSystem = new MgrsGridSystem();

map.addLayer(new UniversalGraticule({ gridSystem, style: { edgeLabel: true } }));
map.addControl(new CursorPositionControl({ gridSystem }));

What you'll see:

• Grid Zone Designators at low zoom, the 6° × 8° UTM zones with their letter band suffix (32U, 33T, etc.).
• 100 km squares as you zoom in (WL, XM, …), with the column-letter set rotating per zone per the MGRS spec.
• Norway / Svalbard exceptions drawn correctly (zone 32V is widened to cover western Norway; zones 31X / 33X / 35X / 37X cover Svalbard while 32X / 34X / 36X are absent).
• UPS regions above 84°N and below 80°S, with their A/B/Y/Z grid letters and 100 km squares.

The CursorPositionControl reads out a full MGRS reference like 32U LB 12345 67890 (variable precision based on zoom).

Options

| Option | Type | Default | What it does | |---|---|---|---| | targetScreenPx | number | 100 | Desired minimum spacing (px) between major lines. Drives interval selection. | | densificationPoints | number | 100 | Points per grid line for curved rendering. |

Coordinate conversion helpers

For non-rendering use (e.g. showing an MGRS string in a popup), the package re-exports its low-level conversion utilities:

import { lonLatToMgrs, formatMgrs } from '@zwaarcontrast/ol-graticule-mgrs';

const ref = lonLatToMgrs([7.0, 48.5], 5);  // -> "32U LB 12345 67890"
formatMgrs(ref);                           // -> "32U LB 12345 67890"

Precision is the number of digits per axis: 0 (GZD only) through 5 (1 m precision).

Exports

Grid system

• MgrsGridSystem, MgrsGridSystemOptions, plug into UniversalGraticule / CursorPositionControl.
• MgrsIntervals, the spacing strategy used internally (re-export).

Coordinate conversion

• lonLatToMgrs(lonLat, precision), [lon, lat] → MGRS string.
• lonLatToMgrsParts(lonLat), structured parts ({ zone, band, square, easting, northing }).
• formatMgrs(ref, options?), pretty-print with spaces between groups.
• lonLatToUtm, utmToLonLat, lonLatToUps, upsToLonLat, round-trip helpers between geographic and UTM/UPS coordinates.

Zone / band / square helpers

• UTM: bandLetterFromLatitude, bandLatBounds, zoneBandLonBounds, zoneNumberFromLonLat, utmCrsCode, utmProj4, BAND_LETTERS.
• 100 km squares: columnLetter, columnSetForZone, rowLetter, rowOffsetForZone, squareLetters.
• UPS: upsColumnLetter, upsRowLetter, upsSquareLetters, upsZoneLetter, upsZoneLonLatBounds, upsCrsCode, upsProj4, upsIsNorth.
• Iteration: iterateVisibleGzds, Gzd.

License

MIT.