The UTM (Universal Transverse Mercator Coordinate System) system is a coordinate system that describes position on a map. GPS receivers can display locations with UTM coordinates. Most maps, particularly those for hikers, show UTM coordinates. They are widely used in search and rescue operations, and are increasingly common in tourist guides. This article will show you how to read UTM coordinates.
Step 1. Determine what zone you are in
The world is divided into 60 UTM zones
Step 2. Determine which datum to use
- When using UTM coordinates, you should make sure to use a common UTM datum. For example, you will need to check to make sure your GPS is set to the same datum as your map or guide, or you will need to make sure the search team knows which datum you are using for your coordinates.
- The most commonly used reference datums in North America are NAD 27 CONUS and WGS 84.
- This is how reference datums work. The reference datum is the place on the map against which other places are measured. Choosing a different place to measure from can significantly change the coordinates. If you use different datums on your GPS and on the map, you may end up in the wrong place.
Step 3. Determine the coordinate of this
- The first number in the UTM coordinates is called this.
- It refers to how east you are.
- If you're using a map, look at the numbers along the edge of the map that correspond to the UTM coordinates. The coordinates for this are at the top and bottom of the map.
- If you are going to use a GPS, the coordinate of this is the first number, if it is configured in UTM mode.
- A 1-number change in the coordinate of this, for example from 510,000 mE to 510,111mE, is a change of about 1 m (1 yard) above the ground. If you walk from 510,000 mE to 511,000 mE without changing your north, you will have walked about 1 km (0.62 miles).
- Interpolate the coordinates of this on a grid to determine an exact location.
Step 4. Determine the north coordinate
- The second number in the UTM coordinates is called north.
- North coordinate refers to how north you are.
- If you're using a map, look at the numbers along the edge of the map that correspond to the UTM coordinates. North coordinates are found along the left and right edges of the map.
- If you are going to use a GPS, the north coordinate is the second number, if it is configured in UTM mode.
- A 1-number change in the north coordinate, for example from 510,000 mN to 510,111 mN, is a change of about 1 m (1 yard) above the ground. If you walk from 850,000 mN to 851,000 mN without changing east, you will have walked about 1 km (0.62 miles).
- Interpolate north coordinates on a grid to determine an exact location.
- You can use a plastic UTM grid on a map to interpolate UTM coordinates very precisely. However, you must be careful to ensure that the scale of this tool matches that of the map. A common problem is that the tool and map scales are different, which can lead to incorrect coordinates or traces.
- The most common problem when using UTM coordinates is that the UTM datums do not match. If you have a problem using UTM, the first thing you should check is that all the maps, books and GPS systems you use have the same UTM datum.