My question is about the best way to convert from NAD 83 to WGS 84 in PostGIS.
I have a PostGIS DB containing National Elevation Data rasters. The rasters are in NAD 83 and I would like to convert them to WGS 84 but PostGIS treats NAD 83 and WGS 84 as the same (see here and here) even though they may differ by over a meter.
I figure that I can just add a new spatial reference identifier with non-zero values for the transformation to WGS 84. So basically this below except with TOWGS84[0,0,0,0,0,0,0] replaced with the correct values.
INSERT INTO "spatial_ref_sys" ("srid","auth_name","auth_srid","srtext","proj4text") VALUES (9999,'EPSG',4269,'GEOGCS["NAD83",DATUM["North_American_Datum_1983",SPHEROID["GRS 1980",6378137,298.257222101,AUTHORITY["EPSG","7019"]],TOWGS84[0,0,0,0,0,0,0],AUTHORITY["EPSG","6269"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4269"]]','+proj=longlat +datum=NAD83 +no_defs ');The problem is that I can't find what those values should be, as in both what the values should refer to and what the value of the values are.
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I have a PostGIS DB containing National Elevation Data rasters. The rasters are in NAD 83 and I would like to convert them to WGS 84 but PostGIS treats NAD 83 and WGS 84 as the same (see here and here) even though they may differ by over a meter.
I figure that I can just add a new spatial reference identifier with non-zero values for the transformation to WGS 84. So basically this below except with TOWGS84[0,0,0,0,0,0,0] replaced with the correct values.
INSERT INTO "spatial_ref_sys" ("srid","auth_name","auth_srid","srtext","proj4text") VALUES (9999,'EPSG',4269,'GEOGCS["NAD83",DATUM["North_American_Datum_1983",SPHEROID["GRS 1980",6378137,298.257222101,AUTHORITY["EPSG","7019"]],TOWGS84[0,0,0,0,0,0,0],AUTHORITY["EPSG","6269"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4269"]]','+proj=longlat +datum=NAD83 +no_defs ');The problem is that I can't find what those values should be, as in both what the values should refer to and what the value of the values are.
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