[gdal-dev] raster reproject fails without error message with GCP_HOMOGRAPHY option

[Andrew C Aitchison]

On Wed, 21 May 2025, Schumacher, Mia via gdal-dev wrote:

>> I am trying to use new gdal raster reproject to georeference image chunks 
>> using ground control points. I figured that for some of these chunks, due 
>> to ship movement, the lower left & lower right image coordinates are 
>> switched, which (understandably) leads the algorithm to fail. however, 
>> there is no error message, it just doesn't produce output. I use:
>> 
> gdal raster reproject -r bilinear --to SRC_METHOD=GCP_HOMOGRAPHY --co 
> COMPRESS=DEFLATE -d EPSG:4326 -i 2025-03-17_08-30-44_0_ch0_0_chunk_tmp.tif -o 
> 2025-03-17_08-30-44_0_ch0_0_chunk_tmp_WGS84.tif
>> 
>> with gcps applied like so:
>> 
>
> gdal_translate -of GTiff \
> -gcp im_x_ul im_y_ul lon_ul, lat_ul \
> -gcp im_x_ur im_y_ur lon_ur, lat_ur \
> -gcp im_x_ll im_y_l lon_ll, lat_ll \
> -gcp im_x_lr im_y_lr lon_lr, lat_lr
> (ul/r, ll/r = upper/lower left/right) --> but sometimes, ll and lr are 
> switched
>> 
>> I would love to catch the error to adjust those files - Is there something 
>> like a verbose mode for gdal raster reproject? Then i could see what is 
>> going on?

gdal_translate --debug on
might give you more information.

(I am also not sure that your have the right numbe of commas
  in the line above.)

-- 
Andrew C. Aitchison                      Kendal, UK
                    andrew at aitchison.me.uk