[Qgis-user] QGIS for surfaces documentation (of Mural Painting)

[Giacomo Marchioro]

Hi all,
I would like to use QGIS for surfaces documentation (in my case: mural
painting...). My main problem is to set a scale to the raster file. Of
course I have no latitude or longitude, however,  I'm using the
georeferencer plugin to "georeference" the raster, because if I don't
"georeference" the image, I can't use others plugin such Polygonize
plugin...) but It's quite difficult because I have to use a trigonometric
trick to convert the parameters in distance. I tried to set a user defined
coordinate system more closer to a plane using the proj4 guidelines, but
all my attempts to simplify the matter fails. What can I do? Are there any
other methods to set a user scale and set a very very user defined
coordinate system? Thanks a lot!

Best regards,
Giacomo Marchioro
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