Topographic map guide

Latitude–Longitude vs UTM Grid

Latitude and longitude locate points with angular coordinates on the Earth, while UTM uses projected metre-based easting and northing coordinates inside zones. Both describe position, but they use different units and geometry.

Latitude

Lines of latitude run east–west and connect points with the same angular distance north or south of the equator. Latitude is expressed in degrees.

Longitude

Meridians run between the geographic poles. Longitude expresses angular position east or west of the prime meridian. Meridians converge toward the poles, so a degree of longitude does not represent the same ground distance at every latitude.

What does a latitude–longitude grid show?

On a topographic map, a latitude–longitude graticule lets you read geographic coordinates in degrees, minutes and seconds or decimal degrees. How those curved-earth reference lines appear on a flat map depends on the map projection.

What does a UTM grid show?

UTM uses the Transverse Mercator projection and divides the world into 60 principal zones. Positions are expressed with a zone plus metre-based easting and northing values.

Is UTM more accurate?

No. USGS notes that UTM and latitude–longitude are different coordinate representations; one is not inherently more accurate than the other. UTM is often convenient on topographic maps because its grid values are expressed in metres.

True north and grid north

True north follows the meridian toward the geographic North Pole. Grid north follows the north direction of the projected grid. The two can differ because a curved surface is being represented on a flat map.

Which should you use?

Use latitude–longitude when you want globally familiar geographic coordinates. Use UTM when metre-based grid work is more convenient. TopograpMaps can display either system or both at the same time.

For UTM zones and easting/northing in more detail, see What Is a UTM Grid?.