[gdal-dev] OGR VRT - affine transform ?

[Jukka Rahkonen]

Frank Warmerdam <warmerdam <at> pobox.com> writes:

> 
> 
> Julien,
> I am not aware of any existing way to do this.  I might be nice if an OGR
VRT could apply something like this on the fly, but that doesn't exist
currently.


I wonder if it could be done by using the Spatialite SQL dialect and
ScaleCoordinates or ReflectCoordinates
http://www.gaia-gis.it/gaia-sins/spatialite-sql-4.0.0.html#p15

This SQL is changing the sign of y-coordinates
select ScaleCoords(geometry,1,-1) from polygons limit 1

And a quick test:
Case 1
======

ogrinfo -ro cities.shp  -dialect SQLITE -sql "select GEOMETRY from cities"
INFO: Open of `cities.shp'
      using driver `ESRI Shapefile' successful.
.....
OGRFeature(SELECT):0
  POINT (23.903381170918806 66.586845471705118)


Case 2
======
ogrinfo -ro cities.shp  -dialect SQLITE 
-sql "select ScaleCoords(GEOMETRY,1,-1)  from cities"
INFO: Open of `cities.shp'
      using driver `ESRI Shapefile' successful.
.....
OGRFeature(SELECT):0
  POINT (23.903381170918806 -66.586845471705118)

At least the query makes y coordinate negative but I am not sure if that was
the meaning.

-Jukka Rahkonen-