Universal Transverse Mercator (UTM)

Universal Transverse Mercator is a modern coordinate system developed in the 1940s. It’s similar to latitude and longitude, but it uses meters instead of degrees, minutes, and seconds. UTM coordinates are very accurate, and the system is pretty easy to use and understand.

Although the United States hasn’t moved to the metric system, the system is widely used by GPS receivers. UTM coordinates are much easier than latitude and longitude to plot on maps. The two key values to convert metric measurements are

• 1 meter = 3.28 feet = 1.09 yards. For ballpark measurements, a meter is a bit over a yard.
• 1 kilometer = 1,000 meters = 3,280 feet = 1,094 yards = 0.62 miles.

For ballpark measurements, a kilometer is a bit more than half a mile. The UTM system is based on the simple A, B, C/1, 2, 3 coordinate system. The world is divided into zones:

• Sixty primary zones run north and south. Numbers identify the zones that run north and south.
• Twenty optional zones run east to west.

These zones indicate whether a coordinate is in the Northern or Southern Hemisphere.
Letters designate the east/west zones.
Often the letter is dropped from a UTM coordinate, and only the zone is used to make things simpler. For example, because most of Florida is in Zone 17 R, if you were plotting locations in that state, you could just use Zone 17 in your UTM coordinates. To provide a precise location, UTM uses two units:

• Easting: The distance in meters to the east from the start of a UTM zone line The letter E follows Easting values.
• Northing: The distance in meters from the equator The letter N follows Northing values.

There’s no such thing as a Southing. Northing is used in the Southern Hemisphere to describe the distance away from the equator, even though a location is south of the Equator. (Is that weird, or what?) Continuing with my example of Dillon Falls, if you use UTM to locate the falls, the coordinates look like this:

10T 0627598E 4868251N

That means that the falls are in Zone 10T, which is 4,868,251 meters north of the equator and 627,598 meters east of where the zone line starts. (For those of you without a calculator in front of you, that’s about 3,025 miles north of the equator, and about 390 miles east of where the number 10 Zone line starts out in the Pacific Ocean.)