[GRASS-user] Help with Georeferencing

[Hamish]

Matt:
> > At the moment I'm trying to georectify a stitched
> > together google earth image

often r.in.wms / r.in.onearth is just as good and totally free.
(r.in.onearth from wiki addons)

> > I've imported the raster into grass using gdal, it
> > splits it up into 3 (RGB) files? and I can display it (in
> > the wrong place at the wrong scale). I also have the
> > coordinates of the 4 corner points of the image and those
> > are what I'm using to georeference using the
> > georeferencing tool from the file menu.

in that case, avoid all the hassle and just use r.region.


Moritz:
> In which location are you running the georeferencing tool ?
> You have to run it in the target location, not in the
> location where you imported your original images.
> 
> Workflow:
> 
> - create two locations, one XY (unprojected) and one
> projected in the reference system you want to georeference
> the images into (AFAIR, Google Earth uses WGS84 lat-long,
> alias EPSG code 4326
> - import images with r.in.gdal into the XY location
> - in the projected location, run georectifying tool


wiki FAQ entry:

  http://grass.osgeo.org/wiki/Georeferencing


Hamish