Forum: Just Getting Started In Geocaching
Topic: UTM Coordinates
started by: ae708

Posted by ae708 on Sep. 20 2004,5:59 am
I saw someone in another post mention UTM coordinates... whut dat is???  Seriously, would someone enlighten me please.. thanks.
Posted by Quinn on Sep. 20 2004,3:38 pm
"UTM" stands for Universal Transverse Mercator. This is just another type of entry one can make in his/her GPSR.
Most people use wgs84 in a MM.MMM fashion. If you would like to learn more about this and other formats try this link < GUIDE TO USING UTM COORDINATES. >

Posted by ae708 on Sep. 21 2004,5:47 am
Thank you..
Posted by whiteurkel on Sep. 23 2004,9:05 pm
Quote (Quinn @ Sep. 20 2004,5:38 pm)
"UTM" stands for Universal Transverse Mercator. This is just another type of entry one can make in his/her GPSR.
Most people use wgs84 in a MM.MMM fashion. If you would like to learn more about this and other formats try this link < GUIDE TO USING UTM COORDINATES. >

Yes, UTM topographic maps are basically a U.S. military thing, what was used before GPS existed. And I'm sure you know GPS is a U.S. military thing as well  :grinnin

The U.S. Military has every inch of the planet covered on UTM Topographic Maps.  

An Excellent link given above. A 4 digit UTM coord is supposed to bring you within 1,000 Meters of your location, a 6 digit UTM coord within 100 Meters of your location, and an 8 digit UTM coord within 10 Meters of your location.

As an old military map reading geek, I'm always telling myself I'm going to switch the GPSr over to UTM, and find a cache that way, but never get around to it; maybe this thread will give me the kick in the butt I need to try it.

Posted by epicanis on 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...

Posted by virgo91967 on Sep. 30 2004,10:42 am
< Colorado State UTM explanation > will tell youmuch more about the basics of UTM


the reason I prefer UTM is that it is so much easier to do the math for distances between points and that it has a better inherant precision that is much better than what I can get from my old maggie310.  My GPSr is only precise to two decimal places ( or about roughly 5 feet) wheras UTM is naturaly precise to 3.25 feet ( one Meter) whereas with Lat/Lon two decimal ppaces are only good for abt 71 feet  

1 Degree = abt 80.5545 Statute ( 70 Nautical) miles. there are 5,280ft to a statute mile. so there are 425 327.76 feet to a degree. divide by 60 minutes gives 7,088.796 feet to a minute and 118.1466 feet to a second. 1/10th (.1)minute = abt 709 feet . 1/100th (.01) min = abt 71 feet and 1/1000 (.001) min = about 7.1 feet. World atlas.com and Distance unit conversion source


No nasty messing about with conversion factors of degreees/seconds into feet if distances  are needed

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