[Qgis-user] ogr2ogr - how to use -s_srs, -t_srs and -a_srs

[Siki Zoltan]

Dear Erik,

if there is a .prj file to your shape and it is valid you need not to use 
-s_srs. Only one of -a_srs and -t_srs is neccessary in your case, if you 
want to reproject coordinates use -t_srs. If you want only change the 
projection but not the coordinates use -a_srs.

Best regards,
Zoltan

On Sun, 6 Aug 2017, Erik Josefsson wrote:

> Hello,
>
> I have a handful of zip archives containing original shapefiles with
> different coordinate reference systems (e.g. SGER:3008 and SGER:3021).
>
> I want to extract and convert them all to SGER:3006 and thought that
> ogr2ogr would do the job, but I don't find intelligible instructions on
> how to use the srs-parameters: -s_srs, -t_srs and -a_srs.
>
> Do I have to know the coordinate reference system of each original shape
> file to use ogr2ogr successfully? If so, how do I retrieve that information?
>
> Or should I just override the original coordinate reference system like
> this?
>
> ogr2ogr -f 'ESRI Shapefile' -s_srs EPSG:3006 -t_srs EPSG:3006 -a_srs
> EPSG:3006 A.shp B.shp
>
> Best regards.
>
> //Erik
>
>