[GRASS-user] Rotate raster map?

[Rich Shepard]

On Tue, 24 Sep 2019, Markus Neteler wrote:

> See
> https://grass.osgeo.org/grass78/manuals/r.in.gdal.html#notes
> "Georeferencing If the dataset has affine georeferencing information,
> this will be used to set the north, south, east and west edges.
> Rotational coefficients will be ignored, resulting in incorrect
> positioning for rotated datasets."

Markus,

I've read that and still fail to understand what to do with this knowledge.

> https://grass.osgeo.org/grass78/manuals/r.in.gdal.html#error-messages
> "... the image must be first externally rotated, applying the rotation
> info stored in the metadata field of the raster image file. For
> example, the gdalwarp software can be used to transform the map to
> North-up (note, there are several gdalwarp parameters to select the
> resampling algorithm):
>
> gdalwarp rotated.tif northup.tif
> "

Ah, I don't recall seeing this. I'll read it more closely and futz with
gdalwarp to fix this class of problems. Then I'll focus on why r.in.gdal
fails to read the hdr.adf files on some maps.

Thanks very much,

Rich