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Tip of the Day 10/5:What the Heck is UTM?

In our weekly Tech Tuesday tip,we tell you how to use technology to help you geocache.

When you look up a geocache on geocaching.com,you might notice alternative coordinates buried in almost apologetically small type under the main coordinates. They look like this:

UTM:19T E 300347 N 4684268

What the heck is that,you wonder? It’s the same coordinates in Universal Transverse Mercator (UTM),an alternative to the WGS84 datum format that a lot of people think is better and more accurate.

UTM uses kilometers and meters instead of degrees,minutes and seconds. It also divides the world into 60 equal sections of 6° each. Each of these grids is then subdivided into kilometers,meaning that the numerical designations in a UTM coordinate are actually distances rather than degrees.

This is really important.. When you use absolute distances,there is no need to adjust for the  variances caused by the curvature of the earth. There are also no positive or negative designations to cause confusion. Also,square grids allow for more precise measurement than curved parallels.

To try to make it simpler (or more more complex,we’re not sure) understand that absolute distances are impossible to standardize using standard longitudes and latitudes because the Earth is spherical. That means that 1° of distance at the equator is completely different from 1° at the poles. Distance measurements based upon longitude and latitude are relative to one’s position on the Earth.

UTM was developed by the United States Army Corps of Engineers in the 1940s to create an alternative view of the world in which distances were consistent. You can read all about it on Wikipedia . The net result is that UTM can make it somewhat easier to find a specific point on the planet because the distances are consistent regardless of where you are. The image below depicts the world as seen on a UTM grid.

Geocaching.com automatically downloads coordinates in UTM format if your GPS is ready for them. It might be worth a try,since several geocachers have sworn to us that it’s easier to search for a location using UTM than WGS84. Be sure you set up your GPSr to receive UTM,becauseif it doesn’t know what’s coming,it will flake out all over the place. Frankly,we haven’t had the time to stage a formal comparison ourselves,but we sure would appreciate your comments here.

Which do you use and why?

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