Other Coordinate Systems

This page is a catch-all for the location systems you'll meet beyond the big four — lat/lon, UTM, MGRS, and USNG. Two come up most often: other countries' national metric grids, and the Public Land Survey System, the land-description grid used across much of the United States.

UTM isn't the only square metric grid

UTM, MGRS, and USNG are the metric grids most people in the U.S. encounter, but they aren't the only ones. Many countries publish their own national grid: the British National Grid, the Irish Grid, and various UTM-like national systems across Europe and beyond. They all share the same basic idea — a square grid measured in meters, laid over a map projection, with easting and northing read off the grid lines.

The practical takeaway: the skills you learned for UTM transfer. Identify the grid square, measure how far east and how far north your point sits inside it, combine that with the printed grid labels. The mechanics are the same; only the projection underneath and the labeling conventions differ.

Why your MapTools ruler still works

Here's the part that matters when you're standing over a foreign map: a MapTools grid tool, slot tool, or ruler reads in meters, so it works on any square metric grid — not just UTM. The tool doesn't know or care whether the grid lines belong to UTM, the British National Grid, or an Irish map. It only cares about one thing:

The tool's scale must match the map's scale.

If you have a 1:25,000 tool and a 1:25,000 map with a 1,000-meter grid, the tool reads that grid correctly regardless of which national system drew it. The 1,000-meter square on the British National Grid is the same physical size as a 1,000-meter UTM square, so the same marked edges measure it. This is why a single metric ruler at the right scale is so useful when you travel — see Map Scale for matching tool scale to map scale.

What to watch for

Three cautions when working with a non-UTM national grid:

The numbers don't mean what UTM numbers mean. Eastings and northings are measured from that grid's own origin, not UTM's. Don't hand a British National Grid coordinate to someone expecting UTM — they'll plot it in the wrong place.
Set your GPS to match the grid. To read or enter coordinates in one of these other square metric grids, change your GPS's coordinate (position) format to that grid system — British National Grid, Irish Grid, and the like are standard options on most receivers. With the format set to match, the numbers your GPS shows line up with the numbers printed on the map.
For coordination across teams or borders, fall back to UTM or lat/lon. National grids are great for in-country navigation but aren't universal. When a coordinate has to cross from one team or country to another, convert it to UTM or latitude/longitude — the systems everyone agrees on. The catch: the map may force your hand. If your map is only printed with one grid, you have to work in the coordinate it shows — so match your tool and GPS to the map first, and convert for sharing second.

Land descriptions: the PLSS

Not every grid printed on a map is a position system. The Public Land Survey System — township, range, and section — divides much of the U.S. into one-mile squares to describe land, not to position it. Its red, center-numbered sections are easy to mistake for a coordinate grid, but they're the framework legal land descriptions are written against — they answer "how is this parcel described?" rather than "where am I?" See Public Land Survey System (PLSS) for how to read a legal land description and why it isn't a substitute for a metric coordinate.