Perhaps you can find some relevant information on the Wikpedia page describing the ESRI world file format: https://en.wikipedia.org/wiki/World_file - that usually where I go when I need to re-learn the basics of affine transformations
/thomas Den man. 21. dec. 2020 kl. 12.34 skrev G Seiffert <h...@posteo.de>: > Hi all from GDLA. > > Thanks for the opportunity to as a question. It's regarding the Geotransform > Tutorial (https://gdal.org/tutorials/geotransforms_tut.html). Tried to > get info in the web but since this seems a tricky one, my searches failed. > > The tutorial only deals with the ideal case of 'North up' images, for > which GT(2) and GT(4) are zero. However, my images are 'East up' and > potentially 'any direction up' (underwater photomosaic surveys by ROV). The > rotation works with '90' for GT(2, 4). But the scaling seems completely > ignored. Any hint? If it would be easy, I assume your tutorial would give > an example for how to deal with "non-N-up' images, but ... > > My pics are 1920x1080, with pixel resolution of 0.0015 (yes, 0.15cm per > pixel, we're flying just 3m above the bottom). > > In case I rotate the images prior to geotransform (in Photoshop), > geotransform works perfect, with GT(2, 4) = 0. Scaling spot on. I can live > with that for our last survey but I'm also looking for a solution in case > our survey heading cannot be 0, 90, 180, or 270, but has to be something > like 35° (due to bottom currents etc.). > > Best regards, any hint qappreciated, > Gerhard > > > _______________________________________________ > gdal-dev mailing list > gdal-dev@lists.osgeo.org > https://lists.osgeo.org/mailman/listinfo/gdal-dev >
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