Gdalwarp using parameters from one coordinate system directly to another

[Ausrod]

I have used gdalwarp successfully to warp images. However I have parameters for a new set of images that are from one coordinate system to another rather than from each to WGS84.

I think this would be a useful enhancement to allow transformations of this type.

Apologies if this can already be done and I am ignorant of it. I have searched extensively.

Regards Rod

[warmerdam]

Reprojection of images (changes of coordinate system) is the primary usecase for gdalwarp. For instance a command like:

  gdalwarp wgs84.tif -t_srs "+proj=utm +zone=11 +datum=WGS84" utm11.tif

would reproject the input image to UTM 11 WGS84 coordinate system.

[Ausrod]

Sorry frank I may not have explained myself correctly. I have an image in GDA94 coordinate system and I wish to change it to SCC (based on AGS66) and i have my seven parameters to change from AGS66 to GDA94 but I do not have parameters to be used in the TOWGS84 values for a wkt file.

Rod

[warmerdam]

Ah, your point then is that you want to be able to perform coordinate system transformations where you provide a datum to datum transformation based on 7-parameter shifts without going through the WGS84 pivot datum. Is that right?

This is not properly supported though in some cases you can fool the machinery - particular if the ellipsoid of one of the datums is essentially the WGS84 ellipsoid.

Are you proposing a solution, or just requesting support for this capability?

To be honest I'm not all that keen on "I want a pony" type enhancement requests filling up Trac.

[Ausrod]

Yes that right. I have tried the workaround and got OK results. No I haven't a solution. Only mentioned in case there are others that wanted the same pony. Lets call him Express. Thanks Rod