Universal Transverse Mercator (UTM)

July 15th, 2005

A side project that I'm currently working on, involving maps, had a bit of data that I was unfamiliar with. I'll start by saying that I'm very familiar with Latitude/Longitude - it's something that everyone learns in school. However, the data that I was provided with was of an entirely different sort and labeled as 'Easting' and 'Northing'. A couple Google searches later brought me to a an article explaining the concept of something called Universal Transverse Mercator (UTM). The article is very math heavy, but the premise is: The earth is broken down into tiny 'zones' around the ecuator and extending northing and south. Within these zones a measurement, in metres, is taken both to the north and to the east of the ecuator. So your final figure is something like Zone: 17, Easting: 300,000, Northing: 4,000,000 (I just made those numbers up). The reasoning for this is that if your measurements are within a tinier 'slice' of the world, your results immediately become more accurate (especially considering the curvature of the earth). Here's a figure showing all the different zones, taken from this page on different coordinate systems:

Now, using that chart above I determined the zone in which I needed to run all my coordinates through - but the problem is: How to convert them into Lat/Long - which every piece of mapping software understands. There are a number of Java Applets which will do this task, but I wanted something that I could automate. This is where Perl, as always, comes to the rescue - there is a module for it! The module is very lightweight, it simply implements the algorithms specified in the article, mentioned before. Useing that module I was able to quickly run through my data and get perfect numbers out - concluding my UTM adventure. As always, more information can be found on Wikipedia.

Tags: maps, geography, data, conversion, utm, geo

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