[FWTools] Questions about gdalwarp from fwtools-linux distribution

Frank Warmerdam warmerdam at pobox.com
Wed Oct 10 17:21:48 EDT 2007

Giannakos Apostolos wrote:
>  First in my case i want to be able  to import the same input and 
> reference gcps in each erdas imagine (hfa) img so as to perform 
> geometric correction and then resample procedure for a great number, 
> more than 300 of raw(without spatial reference) erdas images. How can i 
> import my gcps in a way that i do not have to type them for each image 
> when i am executing gdalwarp command?


I'm not sure of a convenient way to get them from the existing binary
support files into a script that could use them with gdal_translate.

Note, you need to copy the data to a new GeoTIFF file with gdal_translate
in order to attach GCPs that can then be used by gdalwarp.

> Furthermore i did not understand what -multi option does? Is there a way 
> the procedure could be automatically done? 

The -multi switch is intended to do the warp in two threads in order
to try and squeeze a bit of extra performance out.  It does not relate
to warping multiple images.

 > I think that -srcfile
> -dstfile option limits the batch capabilities in away that for each time 
> i use the gdalwarp i have to specify the input and output image. Can i 
> specify input and output folder for all my images   instead of this 
> single and time consuming procedure?

No.  You would need to write a script that can loop over the files,
and invoke the commands once for each.

If this is going to be difficult for you, then I think getting the
GCPs into the correct form is going to be essentially impractical and
that you might be best just doing this process manually with Imagine.

If you *really* want to automate things, it would be possible to write
a small program that would extract the gcps from the binary file, and
write out a .bat file or equivelent suitable to run all the files.
But the cost/effort of doing so will likely be more than the cost/effort
of just running the images manually.

I'd add that Imagine has scripting capabilities, so you might also
consider scripting it within Imagine though I don't know where one
would start with such a task.

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    | President OSGeo, http://osgeo.org

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