Hi I'm trying to convert from WGS84 (or NAD83, I do not mind) to "MTM zone 1 + CGVD28 height" in Canada. I know that the area of use of "MTM zone 1" and "CGVD28 height" do not intersect. But they told me "Canadian agencies still require this datum [CGVD28] throughout all of Canada." Actually the geoid model grid file [ca_nrc_HT2_1997.tif: Canada, Natural Resources Canada, NAD83(CSRS)v2 (EPSG:8235) to CGVD28 height (EPSG:5713)] covers much more than the CRS area of use.
projinfo says something that makes sense to me: PROJ_NETWORK=ON projinfo -s EPSG:4979 -t EPSG:32181+5713 -o proj --spatial-test intersects Candidate operations found: 303 ------------------------------------- Operation No. 1: unknown id, Inverse of NAD83 to WGS 84 (6) + NAD83 to NAD83(CSRS)v2 (1) + NAD83(CSRS)v2 to CGVD28 height (1) + Inverse of NAD83 to NAD83(CSRS)v2 (1) + MTM zone 1, 4.55 m, unknown domain of validity PROJ string: +proj=pipeline +step +proj=axisswap +order=2,1 +step +proj=unitconvert +xy_in=deg +xy_out=rad +step +inv +proj=vgridshift +grids=ca_nrc_HT2_1997.tif +multiplier=1 +step +inv +proj=hgridshift +grids=ca_nrc_NA83SCRS.tif +step +proj=tmerc +lat_0=0 +lon_0=-53 +k=0.9999 +x_0=304800 +y_0=0 +ellps=GRS80 But cs2cs is not doing any vertical transformation: echo 47.741422 -53.613219 0 | PROJ_NETWORK=ON cs2cs EPSG:4979 EPSG:32181+5713 --3d 258814.79 5289330.04 0.00 Running with PROJ_DEBUG=3 it ends with Using coordinate operation Inverse of Transformation from CGVD28 height to WGS 84 (ballpark vertical transformation, without ellipsoid height to vertical height correction) + Inverse of Ballpark geographic offset from NAD83 to WGS 84 + MTM zone 1 that makes sense with the no-change in elevation. Why is that happening? I do not care so much about the version of NAD83. I tried with some and I get the same result. The same with the source CRS. I use WGS84, but can be any flavour of NAD83. Thanks. .___ ._ ..._ .. . ._. .___ .. __ . _. . __.. ... .... ._ .__
_______________________________________________ PROJ mailing list [email protected] https://lists.osgeo.org/mailman/listinfo/proj
