North arrows and declination diagram
The diagram of three lines in the margin of a USGS topographic map shows three different norths: true north (the star), grid north (GN) and magnetic north (MN, with a half arrowhead). The angles between them are the declination.
Easily confused with
How to read it
The USGS explains that most of its topographic maps carry a diagram at the bottom with three north arrows and the angles between them; some very old maps do not. The star is true north, the direction of the line of longitude through the map. MN is magnetic north, where a compass pointed when the map was published. GN is grid north, the direction of the map’s plane grid, on current US Topo maps the UTM grid.
The USGS says magnetic north moves over time, so the declination printed on an old map may no longer be accurate. Its 2001 fact sheet adds that the angle drawn in the diagram is only a picture: the true values are the numbers printed beside it.
Also searched as: declination diagram, grid north, magnetic north, MN and GN on a map, north arrow, star on a topographic map, true north.
These pages describe what each symbol on a map shows. They are not navigation instructions: the map’s own legend says what each of its symbols means, and symbols differ between map series and editions.
Differences by country
Natural Resources Canada prints magnetic declination and the UTM grid information in blue. Ordnance Survey maps give the difference between grid north and magnetic north in the legend, and the OS says it ranged from 0° to 5° across Great Britain when its map-reading leaflet was written, changing every year.
Look-alikes
On an architect’s plan a single arrow marked N is a north arrow: one north, with no declination.
Read next
- Next in Topographic map symbolsScale barThe scale bar is the divided bar in the map margin for reading distances off the map. Each segment stands for a set distance on the ground, such as a mile or a kilometre, and the left end is divided more finely.
- The same shape in Certification marksStar-K kosher symbolThe kosher symbol of STAR-K, a nonprofit certification agency based in Baltimore: a K inside a five-pointed star.
More topographic map symbols
The same shape elsewhere
Browse symbols drawn with arrows, letters and numbers or stars.
Sources
- What do the different north arrows on a USGS topographic map mean?, USGS FAQ, U.S. Geological Survey, FAQ answer
- Finding Your Way with Map and Compass, USGS Fact Sheet 035-01, March 2001, U.S. Geological Survey, From here to there: determining direction
- Topographic Maps: The Basics, Centre for Topographic Information guide, Natural Resources Canada, What do the colours mean?; compass bearings
- Map reading: from the beginner to the advanced map reader, Ordnance Survey leaflet, Ordnance Survey, Using your compass
Researched, edited and approved by Rory Hansen before publishing. Last reviewed October 9, 2026. How we research
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