[gdal-dev] Implementation of 'projective' algorithm in gdalwarp for georeferencing?

[Schumacher, Mia]

Hi gdal community,

Is there a way to implement the |projective| transformation algorithm
(Fig. 2) which is available in the QGIS georeferencer to the |gdalwarp|
utility?

we developed a tool to process sidescan sonar (underwater acoustic
imagery) data (open source, find the code here:
https://github.com/sonoware/sidescantools). These are roughly three steps:

 1. Find bottom line
 2. Do corrections for slant range & signal attenuation
 3. convert to image, slice image into small chunks and do chunk-wise
    georeferencing using gcps (script sidescan_georeferencer.py
    <https://github.com/sonoware/sidescantools/blob/main/sidescan_georeferencer.py>)
    The last step uses |gdal_translate| and gcps to georeference small
    chunks of the image and |gdalwarp| for the tranformation to geotiff.
    Right now we use |polynomial 1| as transformation algorithm but
    this, as it preserves parallels, leaves gaps between the chunks
    (first pic). In QGIS, there is an option |projective| as
    tranformation algorithm (2nd pic), which does the trick but is not
    implemented in gdal? At least I haven't found it (if I've overseen
    something I'm terribly sorry for bothering!). I would love to help
    if I can.

Image
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Image
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