[R-sig-Geo] Help with latlong to UTM conversion when UTM zones are different

[Andrew Duff]

A number of field folks prefer UTM because 

-it matches legacy paper USGS quad map series traditionally used for field navigation
-units are in meters and can be used to gauge field distances from a coordinate readout 



> On Mar 27, 2015, at 10:48 AM, Michael Sumner <mdsumner at gmail.com> wrote:
> 
> There is no good natural reason to use UTM, it mistifies me why our
> community tolerates this bizarre default. I always use a local equal-area
> projection unless some other compromise dictates a different choice.
> Cheers, Mike
> 
> On Fri, 27 Mar 2015 21:28 Barry Rowlingson <b.rowlingson at lancaster.ac.uk>
> wrote:
> 
>> If you have lat-long data that crosses two UTM zones then its
>> generally okay to just pick *one* and transform all the points to
>> that. Use the one that has the most points in. Basically use the UTM
>> zones as guidelines to pick one UTM zone coordinate system. Unless
>> your data spans several zones and you want quite high accuracy of
>> distance measurements. Some points bleeding over into an adjacent zone
>> are no problem.
>> 
>> All projections are approximations to the earth's spheroid, so points
>> that are within a single UTM zone have some distortion in their
>> distance or angle relationships. Transforming points that are within
>> an adjacent UTM zone is just an extension of that distortion. You can
>> compute the precise distance error if you want for the furthest points
>> by comparing with the geodesic distance.
>> 
>> Alternatively you might find there is a coordinate system that spans
>> your dataset nicely - often when a country or an island or a region
>> crosses UTM zones there is an official coordinate system defined that
>> is used by the authorities there.
>> 
>> Also alternatively, there's nothing to stop you defining a transverse
>> mercator system based on the centre of your data.
>> 
>> Barry
>> 
>> 
>> 
>> On Fri, Mar 27, 2015 at 7:44 AM, moses selebatso <selebatsom at yahoo.co.uk>
>> wrote:
>>> Hello
>>> I have animal movement data that I have converted from Lat/Long to UTM,
>> unfortunately the data falls in two UTM zones (34S and 35S). For some
>> reason R cannot display both of them in the same window (the 35S data is
>> way off the expected location).
>>> The question is how do I convert the data such that R can correctly read
>> it?
>>> Moses SELEBATSO
>>> 
>>> (+267) 318 5219 (H) (+267) 716 393 70 (C)
>>>  (+267) 738 393 70 (C
>>>        [[alternative HTML version deleted]]
>>> 
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>> 
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