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GDALWARP & GCPs: msg#00090

gis.gdal.devel

Subject: GDALWARP & GCPs

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?
2. How many GCPs can be provided?
3. Does the image need to be raw or will it work with .tif too?
4. Earlier write up on gdalwarp mentioned that it supported
    nearest neighbour resampling only.  Does it support bilinear
    or any other methods now?

Thanks,

Reinaldo

At 23:30 18-09-03 -0400, you wrote:
Reinaldo Escada Chohfi wrote:
Hi GDAL Users,
I am planning to use the gdalwarp utility to
geo-reference a number of images in batch.
I would like to know before hand if it can be
utilized to warp (rectify) unprojected images.
That is, can it input raw images with GCPs
and output geo-referenced rectified (warped)
Geotiff images, given that it is also provided
proj, zone, ellps, etc?
Or it can only be used to reproject and warp
images that have already been rectified and are
geometrically correct in a particular projection?

Reinaldo,

First, I would advise you to use gdalwarptest, the new generation
warper.

Second, yes, it can rectify raw images, but it can be a bit tricky
currently to supply the GCPs.  Also, currently only polynomial warps
are supported when operating from GCPs, and only up to 3rd order.

Best regards,
--
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam@xxxxxxxxx
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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