New answers tagged utm
The use of datum shift grids for NAD27 is hardcoded in https://svn.osgeo.org/metacrs/proj/branches/4.8/proj/src/pj_datums.c "NAD27", "nadgrids=@conus,@alaska,@ntv2_0.gsb,@ntv1_can.dat", "clrk66", "North_American_Datum_1927", If you get offsets, the grid shift might not ...
I believe that the proj4 faq answers your question about the datum shifts between NAD27 and NAD83.
EPSG:4230 is ED50 lat/long. The proj definition string is: +proj=longlat +ellps=intl +towgs84=-87,-98,-121,0,0,0,0 +no_defs which means that the ED50 ellipsoid is around 100m offset in all three earth-centered directions. The "true" ETRS89 lat/long EPSG:4258 definition is: +proj=longlat +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +no_defs which is almost the ...
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