What is a UTM Map?
Universal Transverse Mercator projection (UTM) is a world geodetic system of map projection that treats the earth as a perfect ellipsoid. It was first devised by the US Army in the 1940s to simplify land navigation.
It is a grid system that divides the world into 60 strips divided by lines pointing to true north with separate zones for the northern and southern of the equator, thereby giving a total of 120 UTM zones worldwide. The system is used to assign coordinates to locations on the Earth’s surface, using each zone as a basis for coordinates.
Each UTM zone is numbered 1-60, beginning at 180-degrees longitude and increasing to the east. Each zone comprises 6 degrees of longitude and has a designated central meridian.
Many hikers prefer to use UTM over latitude and longitude when using 7.5-minute series topo maps—all of which feature 1000m UTM grid tick marks—due to the simplicity of the decimal degrees.
Why is Learning to Read a Universal Transverse Mercator (UTM) Grid Reference Important?
Being able to use a UTM map and read UTM coordinates is important for two reasons: first, it allows you to identify your exact whereabouts on a map using the coordinates given in a GPS device for hiking; second, it allows you to give rescue services your precise location should your trip in the backcountry go south and you need to call for help.
How Do I Read a UTM Coordinate?
Locations in UTM must contain the following:
- A zone number (1—60)
- A zone hemisphere (N or S for Northern Hemisphere or Southern Hemisphere)
- An easting and northing
When reading a UTM coordinate, your reading should state latitude and then longitude (eastings first, then northings). A useful mnemonic to help you remember this is “along the corridor, then up the stairs.”
Let’s use the UTM reference of the Empire State Building as an example:
18 N 585628 4511322
To unpack these numbers, we have to break the reference down into parts:
- 18—The zone number
- N—The Northern Hemisphere
- 585628—The measurement of the East-West position (“UTM easting”), within the Grid Zone, in meters. Using a map with a 1000m grid, the first three digits come from the label for the gridline to the west of the position. The last 3 digits are the distance in meters measured from the western gridline
- 4511322—The measurement of the North-South position (“UTM northing”), within the Grid Zone, in meters. Using a map with a 1000m grid, the first three digits come from the label for the gridline to the south of the position. The last 3 digits are the distance in meters measured from the southern gridline
How to convert between the UTM system vs WGS84 vs Latitude and Longitude?
If you want to change the format from UTM to or from another coordinate system, then we highly recommend you check out the following coordinates converter:
UTM to Lat-Long: http://www.rcn.montana.edu/resources/converter.aspx
*Note we can not confirm the accuracy of any values the calculator generates.
Further Reading: Now you know what a UTM map is, why not learn how to plan a hiking route!