[Freegis-list] Re: tool to find out lat/lon --> UTM

[Cere Davis]

It's even easier than that to code with a simple mod function on the
longitude value but it seems to me that the default dehaviour of proj would
be to assume the zone you are in and give x-y values accordingly.  This is
where I am confused...about the assumption.  Instead proj4 gives you x-y as
if from GMT.  So I think it's something about zones that I don't
understand.  

-Cere

Paul Ramsey wrote:

> Write up 20 lines of perl to wrap around your proj4 call. The zone value
> is a simple categorization on your longitude, so it is trivial to
> script. Possibly why noone has bothered to make such a think automagic.
> 
> P
> 
> Cere Davis wrote:
> 
>> Hi everyone,
>> 
>> I have sort of a basic GIS question that doesn't appear to be all that
>> obvious to me.
>> 
>> I am using the proj4 tools in linux to find at utm X-Y zone value for a
>> given lat-lon value.  I have played around with it for a bit and I am
>> suprised to find that proj requires me to input a default easting zero
>> value (such as +lon_0=120w) in order to get meaningful x-y data for my
>> zone.  To me this seems like redundant information.  If I give my lon_0
>> value then I allready know what zone I am in basicly so this is not very
>> usefull to me.  I suppose I could do some pre math and make some
>> assumptions about the quadrant that my lat/lon value are in to find the
>> lon_0 value before I send arguments to Proj but...  Is there any tool
>> that just allows me to type in a lat/lon and returns a x-y and zone
>> value?
>> 
>> Thanks,
>> -Cere
>> 
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