View Full Version : UTM coordinates to lat/long help

09-25-2013, 12:27 PM
Hello. First time poster / visitor but hopefully I will be able to get some help here as I am stumped.

I ran across a piece of code has a collection of UTM POINTS that takes the point and places it on a map. Now, I have all this data but I need a way to get the latitude and longitude of each point. I have tried many thing but am unable to convert it exactly, always dancing around that area of the world but nowhere near as close as I need it to be.

For example, I have the POINT 735622.1 6588896.1 using the International 1924 datum in zone 35V. I already know the lat/long for this point which is 59.37249,28.147 (I did this one manually but there are hundreds more and I don't want to try to do it manually for all of them). Now, when I put this POINT into any online converter such as Convert Between Geographic and UTM Coordinates (http://www.uwgb.edu/dutchs/UsefulData/ConvertUTMNoOZ.HTM) I get a different lat/long, a hundred or so KM away from my target.

I know there is something more going on in the background though as the code snippet is using more variables than any of the converters. The code snipped looks like this:

latitude = enToLat(x, y, eRadius, pRadius, e, n, f, phi, lam);
and the variables for this are:

eRadius = 6378388;
pRadius = 6356911.94612795;
e = 200000;
n = 300000;
f = 0.99999;
phi = 24.45;
lam = 51.2166666666667;
I am guessing that there is something extra that I am missing regarding the phi and lam variables but I don't know what they are supposed to be representing. The same goes for the variables e, n, f.

If anyone could help me shed a bit of light on what these variables are and what calculations are being done I would be most appreciative.

09-25-2013, 09:43 PM
I think what you need to use is the GDAL package which has bindings for various languages. I would use Perl but I think most would use Python. Here is a link to some code which might be useful...

How to convert from UTM to LatLng in python or Javascript - Stack Overflow (http://stackoverflow.com/questions/343865/how-to-convert-from-utm-to-latlng-in-python-or-javascript)

09-26-2013, 07:57 AM
Thanks for the link. The python script there, with a few slight modifications, worked perfectly. Thanks!