[Gdal-dev] GDALWARP & GCPs

Frank Warmerdam warmerdam at pobox.com
Fri Sep 19 01:31:29 EDT 2003

Reinaldo Escada Chohfi wrote:
> Frank,
> Thanks for the prompt reply.
> Up to 3rd order polynomial warp is fine for my application.
> I'll take a look at gdalwarptest.
> I have a few more questions now:
> 1. How can GCPs be supplied? Is there a write up on it?


There is some earlier discussion of this on the list.  I suggest
you skim back for it, and/or hassle me to write a "gcp adding" utility.

> 2. How many GCPs can be provided?

Any number.

> 3. Does the image need to be raw or will it work with .tif too?

Any GDAL supported format is fine for input.  Note that raw files will
only work if you find a way to describe them to GDAL (ie. .aux file, or
.hdr file).

> 4. Earlier write up on gdalwarp mentioned that it supported
>     nearest neighbour resampling only.  Does it support bilinear
>     or any other methods now?

The gdalwarptest program supports nearest neighbour, bilinear and two
types of cubic resampling.

Best regards,

I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent

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