[Proj] X,Y UTM distance calculation (compare with latlong WGS84)

[Gerald I. Evenden]

On Wednesday 13 September 2006 8:21 am, oon at informatika.org wrote:
>      Dear All,
>
> I want to ask a question about distance calculation of two points in
> X,Y (UTM).
> Is it ok if I get the distance of two points in X,Y (UTM) only with
> distance calculation of cartesian coordinate (pythagoras method)?
> The error getting larger (or getting huge) if I calculate the distance
> with the
> points crossing the UTM zone. (I have tried for point with (1) different
> zone, I don't know what will be happened if the points over more than 1
> zone??)
>
> Is it any other method to get distance calculation of cartesian
> coordinates X,Y (UTM), so the result of the calculation have accuracy
> like distance calculation
> of WGS84?
> (It's ok if the error about hundred meters)
>
> thanks for your help..

Distance (and azimuth) calculation should be done with a program computing the 
geodesic such as 'geod' or the NSG Vincente procedures.  For points within a 
few kilometers of each other the Cartesian coordinates of UTM or other 
appropriate conformal projection can be used where accuracies in the 
decimeters are acceptable.  For precision work, *never* consider cartographic 
Cartesian projection systems.

Calculation of distances across UTM zones is out of the question because each 
zone has its own origin.  Errors would be in the hundreds of kilometers.