Hi I am trying to make this transformation (that is not in EPGS). I do not know how far I can go with PROJ.
(Apparently this transformation is needed to go from the coordinates used by HEPOS.gr, the Greek positioning system, to the official -I think- CRS in Greece, GGRS87. The best is that the transformation would be in EPSG. Do you know anybody in Greece with the proper contacts? I am happy to talk with them about it, and help if needed) Until it is in EPSG, I would like to use PROJ to do it. The accurate transformation from ETRS89 to GGRS87 is something like: - apply a Helmert transformation - Project into a transverse Mercator - Apply a correction grid. Yes, in the projected system. - (optional) go back from the projected to the geographic crs. I thought about several options: - First option: create a WKT2 with a BOUNDCRS that defines the transformation. Can it be done in a single WKT2? - Second option: add the transformation to proj.db. Is it doable? - Third option: Create "my own grid" file (in the geographic system) combining all the steps. Of course, it will loose some accuracy due to the new grid interpolation. Any clue? Thanks.
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