GARS to latitude and longitude
Decodes a Global Area Reference System code (5 to 7 characters) to the center and bounds of its cell, quadrant, or keypad.
The GARS cell is centered at 57.625°, 10.375°.
- Center longitude
- South edge
- West edge
- North edge
- East edge
Provenance
- Computed by
- geodesy.grid-ref.gars-inverse 1.0.0, core 0.1.0
- Model
- GARS as in GeographicLib's GARS class
- Accuracy
- Identical to GeographicLib's GARS class (within 1e-13°)
- Notes
- None
- Cites
- National Geospatial-Intelligence Agency, Global Area Reference System (GARS); Karney, C. F. F., GeographicLib, GeographicLib GARS and Georef classes
Something look off?
How we got thisFormula, worked example, sources, and proof
Model: GARS as in GeographicLib's GARS class
Accuracy: Identical to GeographicLib's GARS class (within 1e-13°)
When to use this: Use this when a GARS code arrives in a message, a plan, or a product and you need the ground it refers to: it returns the center and the bounds of the cell, quadrant, or keypad, at whatever precision the code carries. It is the counterpart to the encoder, so a cell named in a tasking message or an overlay can be drawn on a map with its true extent rather than as a point.
Limitations: The code names a cell, so the true position is anywhere inside it and the center is a convenience rather than the point. Codes of different lengths mean different areas, and a keypad cell is still about nine kilometers across at the equator. No datum is implied beyond WGS 84. The three precisions are nested but very different in size, from thirty minutes down to five, so reading a code at the wrong length puts the area out by a factor of six in each direction.
Worked example: 381NH45. Source: GeographicLib GARS documentation.
You enter
- GARS
- 381NH45
You get
- Center latitude
- 57.625°
- Center longitude
- 10.375°
- South edge
- 57.583333333°
- West edge
- 10.333333333°
- North edge
- 57.666666667°
- East edge
- 10.416666667°
Review: Not yet independently reviewed by a geodesist.
Last verified: 2026-09-18, when a maintainer last confirmed this tool's sources at the issuer. See the sources ledger.
Status: version 1.0.0, core 0.1.0. See this tool in the verification report.
Changes
- 2026-09-19, changed: The GARS, GEOREF, Maidenhead, and USNG tools are stable, both directions. They reproduce NGA's GARS band definitions, the Wikipedia GEOREF (NAS Patuxent River) and Maidenhead (W1AW) examples, and the FGDC USNG Washington Monument, and match GeographicLib, pygeodesy, an exact Maidenhead reference, and NGA GEOTRANS on thousands of points. Results are unchanged apart from the fix below. Changelog
Checked against: 25 golden test vectors (download the test vectors, each with its source and tolerance). See how results are checked and every source.
Sources
- Global Area Reference System (GARS), National Geospatial-Intelligence Agency, NGA GARS web description. 30-minute cells, 15-minute quadrants, 5-minute keypads.
- GeographicLib GARS and Georef classes, Karney, C. F. F., GeographicLib, GeographicLib 2.x. GARS.cpp and Georef.cpp: encoding, decoding, and precision rules. Read free.
Terms
- GARS: Global Area Reference System
- A worldwide grid of 30-minute cells, split into 15- and 5-minute quadrants and keypads, used to name areas. Source: Global Area Reference System