[Proj] Stereo 1970 (EPSG 31700)

[Thibaut Gheysen]

I checked in Arcmap, there are two "geographic coordinate system
transformations" for stereo 1970 to wgs84. I used the first with those
parameters : +towgs84=44.107,-116.147,-54.648,0,0,0,0. The suggested proj.4
definition correspond to the second "geographic coordinate system
transformations" in ArcMap.

All is fine now.

Thanks for your help,
Thibaut.

2010/10/4 Thibaut Gheysen <gheysen.t at gmail.com>

> Thanks Frank.
> I use QGis 1.5 from osgeo4w (I don't know exactly which version of Proj.4
> is used).
> I just try with your suggested definition. It's better but I always have a
> deviation of about 5 meters.
>
> Thibaut.
>
> 2010/10/4 Frank Warmerdam <warmerdam at pobox.com>
>
> Thibaut Gheysen wrote:
>> > Hi,
>> >
>> > I have a problem in QGIS with the Stereo 1970 coordinate system (EPSG
>> > 31700).
>> > I have a shapefile in the WGS 84 coordinate system (from a GPS device).
>> > I projected this shapefile in Stereo 1970 using ArcMap.
>> > In ArcMap, the source and projected points are in the same place. In
>> > Qgis, I have a deviation of about 100 meters when displaying this 2
>> > shapefiles and activating the "on the fly projection" (stereo.jpg). This
>> > deviation is the same that the one I obtain in ArcMap without
>> > "geographic coordinate system transformations".
>>
>> Thibault,
>>
>> I'm not sure exactly what version of PROJ.4 you are using, but after my
>> "datum shift identification upgrade" the EPSG dictionary for proj now
>> has this as the suggested definition of 31700:
>>
>>
>> +proj=sterea +lat_0=46 +lon_0=25 +k=0.99975 +x_0=500000 +y_0=500000
>> +ellps=krass +towgs84=28,-121,-77,0,0,0,0 +units=m +no_defs
>>
>> Perhaps you could try with this?
>>
>> Best regards,
>> --
>>
>> ---------------------------------------+--------------------------------------
>> I set the clouds in motion - turn up   | Frank Warmerdam,
>> warmerdam at pobox.com
>> light and sound - activate the windows | http://pobox.com/~warmerdam<http://pobox.com/%7Ewarmerdam>
>> and watch the world go round - Rush    | Geospatial Programmer for Rent
>>
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>
>
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