[Proj] conversion latlong to UTM (& vice versa)

[Oscar van Vlijmen]

> From: oon-informatika.org
> Date: Thu, 02 Nov 2006 16:22:44 +0700
> Subject: [Proj] conversion latlong to UTM (& vice versa)

...
 
> If I convert from latlong projection to UTM projection,
> I can get the UTM zone from UTM definition, so I can calculate the zone
> from it's longitude.
> 
> If I'm doing vehicle tracking with UTM projection,
> and the vehicle moving between UTM zones,
> How should I do to get UTM zone of current position of vehicle?
> (so I can convert UTM to latlong again).
> 
> Is it any statement or definition of UTM that declare
> how to get UTM Zone from UTM coordinate?
> 
...

I believe it is not possible to derive from the UTM coordinates the zone
number.

For instance,
lat=35, lon=113, zone=49 (central meridian = 111)
gives UTM coordinates (x,y):
682516, 3874871
Exactly the same UTM coordinates are produced for:
lat=35, lon=119, zone=50 (central meridian = 117)

So, there is only one option: convert back from UTM with known zone number
to lat,lon and reconvert in the other zone to UTM.
Or, set the tracking system to lat,lon production!