[Qgis-user] Re: [Qgis-developer] Wrong reprojection if using different datums?

Micha Silver micha at arava.co.il
Mon Jul 13 00:37:59 PDT 2009


Paolo Cavallini wrote:

> Agustin Lobo ha scritto:
>   
>> different in both datums? I suspect that proj4 (behind QGIS)
>> is not using the +towgs= field.
>>
>> Any opinions on this problem?
>>     
>
> Hi Agus.
> I think QGIS is mostly ignoring +twgs parameters. This is the root of
> several bugs, and I think is one of the major issues to be solved.
> Mentioned also in our bug squashing initiative:
> http://www.qgis.org/wiki/Bugs#Projections
> Unfortunately, it did not attract much specific funding jet.
> All the best.
>   
The Israeli CRS also uses a +towgs parameter. This did not appear in the 
srs.db until about a year ago. After I asked on the list, the entry for 
EPSG:2039 was fixed in the srs.db (now equivalent to the proj4 
definition) and since then QGIS has done reprojection with datum 
correction properly (i.e. using v.proj in GRASS gives the same results 
as QGIS projection).
Agus- can you check the entry for your EPSG code in 
/usr/share/qgis/resources/srs.db (sqlitebrowser) and compare with the 
same entry in /usr/share/proj/epsg?

-- 
Micha




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