Are there rasters in a projection different from current location,
registered by r.external -o, reprojected on the fly when used?
Radim
Hi Radim,
Short answer: No.
I see that we should go through the documentation and check for working with these flags. -o just overrides the projection consistency check and uses Location’s projection (overrides dataset projection). It is used when definitions are the basically the same but there is some difference which does not influence the result or when dataset projection is wrong and you simply know that it matches the Location’s projection.
In other words, there is no on-the-fly reprojection, not even with r|v.external. However, when we consider recent addition to addons r|v.in.proj (r.in.gdal and v.in.ogr but with reprojection), r.external with on-the-fly projection would be nice addition too (although much more complicated) but I think that from GRASS point of view the linked dataset would have Location’s projection (reprojection would be done inside library).
Please somebody correct me if I’m wrong,
Vaclav
···
On Sun, May 10, 2015 at 2:29 AM, Radim Blazek <radim.blazek@gmail.com> wrote:
Are there rasters in a projection different from current location,
registered by r.external -o, reprojected on the fly when used?Radim
grass-user mailing list
grass-user@lists.osgeo.org
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Hi,
Maybe a theoretical case (and irrelevant here). I never tried it myself:
Probably it is possible to link a GDAL VRT using r.external, where the CRS of the original data differs from the current locations projection?
Cheers
Stefan
···
Hi Radim,
Short answer: No.
I see that we should go through the documentation and check for working with these flags. -o just overrides the projection consistency check and uses Location’s projection (overrides dataset projection). It is used when definitions are the basically the same but there is some difference which does not influence the result or when dataset projection is wrong and you simply know that it matches the Location’s projection.
In other words, there is no on-the-fly reprojection, not even with r|v.external. However, when we consider recent addition to addons r|v.in.proj (r.in.gdal and v.in.ogr but with reprojection), r.external with on-the-fly projection would be nice addition too (although much more complicated) but I think that from GRASS point of view the linked dataset would have Location’s projection (reprojection would be done inside library).
Please somebody correct me if I’m wrong,
Vaclav
On Sun, May 10, 2015 at 2:29 AM, Radim Blazek <radim.blazek@gmail.com> wrote:
Are there rasters in a projection different from current location,
registered by r.external -o, reprojected on the fly when used?Radim
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user
On Sun, May 10, 2015 at 1:50 PM, Vaclav Petras <wenzeslaus@gmail.com> wrote:
In other words, there is no on-the-fly reprojection, not even with r|v.external. However, when we consider recent addition to addons r|v.in.proj (r.in.gdal and v.in.ogr but with reprojection), r.external with on-the-fly projection would be nice addition too (although much more complicated) but I think that from GRASS point of view the linked dataset would have Location's projection (reprojection would be done inside library).
Something is there:
grass-addons/grass7/raster/r.in.proj/r.in.proj.py
grass-addons/grass7/vector/v.in.proj/v.in.proj.py
(so, use g.extension ...)
Maybe useful as background info since these scripts do a series of tests.
Markus