Joined: Sep. 2004
||Posted: Sep. 23 2004,9:27 pm
Apparently, one benefit of the UTM projection(s) are that they are intended to accurately represent DISTANCE on a map - that is, no matter where the map is centered, the scale of the map at all points stays consistent.
(Or put yet another way - if you have a UTM map that says "1 inch = 500 ft" [or on a computer "1 pixel = 1 meter", for example], and you know where exactly you are on the map and exactly where on the map your target is, you can accurately tell exactly how far in "real" distance you have to go.)
That may seem obvious, but a lot of other map types aren't so accurate. At another extreme, there is a projection referred to as "flat" or "equirectangular" or "latlong" or "geographic" (or "Plate caree'"....), where the scale represents degrees rather than distance (e.g. "1 pixel = 0.0833333 degrees"). That kind of map is extremely easy to work with in a computer program, but the result is somewhat distorted compared to the actual distance the map is supposed to represent. The further away from the equator you are, the more distorted.
As a completely unqualified self-learning amateur, I've probably described this really badly. A book I can highly recommend that explains this stuff better is "How to Lie with Maps", by Mark Monmier...
"Given the pace of technology, I propose we leave math to the machines and go play outside." - Calvin