The numbers and tick marks around the edge of a USGS topo map are coordinate systems. Latitude and longitude ticks let you plot GPS coordinates. The UTM grid lays a simple metric grid over the map for measuring and plotting. State Plane ticks are used mostly by surveyors and engineers. Learn to read them and you can turn any GPS reading into a spot on paper.
How do I read UTM coordinates on a topo map?
UTM ticks along the map edge are 1,000 meters apart and labeled with their grid value. The large digits are kilometers. Connect matching ticks on opposite edges to draw a grid, then read the easting (left to right) first and the northing (bottom to top) second.
IN THIS GUIDE
Latitude and longitude · UTM grid · State Plane coordinates · Plotting a GPS position · FAQ
Latitude and longitude
A standard USGS quad covers 7.5 minutes (one-eighth of a degree) of latitude and longitude, which is why they're called 7.5-minute quads.
Neatline
The map's border, with the latitude and longitude printed at each corner, here 39°15′ N and 90°37′30″ W.
Graticule tick
A tick on the border, labeled in minutes (55′). On 7.5-minute quads, these ticks are every 2.5 minutes.
Graticule intersection
A small cross inside the map where the latitude and longitude lines through the border ticks meet. Connect the ticks to draw a lat/long grid.
Datum shift tick
A dashed cross showing where the map's corner falls in a different datum (for example NAD 27 vs. NAD 83). The shift can be tens of meters, so set your GPS to the map's datum.
UTM grid
Universal Transverse Mercator (UTM) divides the world into zones and measures position in meters east and north. It's the easiest system for measuring distance on a map.
UTM grid (full grid)
Thin black lines across the whole map, every 1,000 meters, labeled at the edges. Each square is one square kilometer.
UTM grid ticks USGS–Forest Service quads
Short blue ticks along the map edge every 1,000 meters. Connect matching ticks with a straightedge to draw your own grid.
State Plane coordinates
Each state has one or more State Plane zones, measured in feet or meters from a local origin. A map that crosses zone lines, or that shows both older and newer versions of the system, carries more than one set of ticks.
Primary zone tick
A black tick labeled in feet (640 000 FEET): the State Plane zone the map is mostly in.
Secondary zone tick
A tick for a second set of State Plane coordinates, here in meters.
Tertiary zone tick
A third set of ticks, for maps that touch additional zones or versions.
Quaternary zone tick
A fourth set of ticks.
Quintary zone tick
A fifth set of ticks, rare and found where several zones meet.
WATCH
Topo Map Reading, part 10: UTM Grids
A one-minute lesson from our Topo Map Reading series.
Also in the series: Part 9: Latitude and Longitude Grids
Watch the full Topo Map Reading series →Plotting a GPS position
- Match the datum. Check the map margin for the datum (NAD 27 or NAD 83/WGS 84) and set your GPS to match.
- Use UTM for quick plotting. Draw the 1-km grid, then use a UTM corner ruler (or just estimate tenths) to place your position within a square.
- Read right, then up. For both UTM and latitude and longitude, find the east-west position first, then the north-south.
- Mind the declination. Grid north, true north, and magnetic north are all slightly different. The margin diagram shows the angles.
PUT IT TO USE
See these symbols on a real map
Frequently asked questions
What's the difference between UTM and latitude/longitude?
Latitude and longitude measure angles in degrees. UTM measures distance in meters within a zone. UTM is easier for measuring and plotting on a paper map.
What are NAD 27 and NAD 83?
They are map datums: models of the Earth's shape that coordinates are based on. Older USGS maps use NAD 27, and newer maps and GPS use NAD 83 or WGS 84. The same point can be tens of meters apart in different datums.
Why are there several sets of tick marks on the map edge?
Each set belongs to a different coordinate system: latitude and longitude, UTM, and one or more State Plane zones.
What is a neatline?
The neatline is the line that bounds the map itself, inside the margin. Its corners are labeled with latitude and longitude.
MORE SYMBOL GUIDES
Contour Lines on Topo Maps: Index, Intermediate & Depression Contours · Benchmarks & Spot Elevations: What BM Means on a Topo Map · Township, Range & Section Lines on Topo Maps
← Back to all USGS map symbols
Symbol artwork from the U.S. Geological Survey Topographic Map Symbols brochure (public domain).