[Qgis-user] coordinate conversion

[Alex M]

Datum Transformation might be a reason. Different implementations of the
calculation could also account for it.
https://trac.osgeo.org/gdal/wiki/FAQCoordinateSystemsAndProjections#WhydoesntGDALautomaticallychoosethedatumtransformation
https://github.com/OSGeo/proj.4/wiki
https://github.com/OSGeo/proj.4/wiki/GenParms (Datum Transformations)

There is always some accuracy/precision loss reprojecting too.

Which UTM Zone 32 proj did you use?

If you really want to see the code, it's in the PROJ4 project.

Enjoy,
Alex

On 11/12/2015 10:01 AM, francesco_lucca wrote:
> Hi,
> I have a point in WGS84 UTM32 coordinate
> 
> E 589747.816
> N 4871699.496
> 
> I saved in EPSG 3003 with the following coordinates:
> 
> E 1589776.553
> N 4871716.117
> 
> A colleague made the same conversion using free software "traspunto"
> (http://www.mondogis.com/traspunto.html) developed by the Italian
> Enviromental Ministry. He got this result (EPSG 3003 coordinates):
> 
> E 1589776.054
> N 4871716.382
> 
> I try another online tool
> (http://www.sardegnageoportale.it/webgis/raswebconverter/index?stato_quale=punto)
> and I found these EPSG3003 coordinates:
> 
> E 1589776.554
> N 4871716.119
> 
> Summary: QGIS and sardegnageoportale seem to give the same results,
> traspunto is different (0.50 meter difference). Which is the correct result?
> Where can I found the calculation for the conversion from a system to
> another?
> 
> Thanks
> 
> Francesco 
> 
> 
> 
> --
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