QGIS doesn't create the correct projections when creating new shp files

Question

I received shapefiles exported from ArcGIS with EPSG:2227 as the CRS, which should be:

+proj=lcc +lat_1=38.43333333333333 +lat_2=37.06666666666667 +lat_0=36.5 +lon_0=-120.5 +x_0=2000000.0001016 +y_0=500000.0001016001 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=us-ft +no_defs

When I loaded it into QGIS, it says that it is a user defined CRS with the lat_1 and lat_2 mixed up and they have slightly different x_0 and y_0 values:

+proj=lcc +lat_1=37.06666666666667 +lat_2=38.43333333333333 +lat_0=36.5 +lon_0=-120.5 +x_0=2000000 +y_0=500000.0000000001 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=us-ft +no_defs

Even when I reproject the .shp from the user CRS to EPSG:2227 and then load it back into QGIS, it says that it is a user-defined CRS.

Has anyone else seen this happen?

Answer 1

ARCGIS shapefiles don't contain EPSG codes, only WKT definitions, so QGIS has to make a guess which one from its own EPSG database fits. In your case, it does not succeed, maybe due to rounding errors for x_0 and y_0. In WKT, they are in feet (like the coordinates), while the proj4 string always uses metres.

You can open the .prj file from ARCGIS and compare it with that of an EPSG:2227 file made by QGIS.

You can savely use SET CRS for Layer to assign EPSG:2227 for the layer. The switched lat_1 and lat_2 has no effect on the coordinates, and the offset in x_0 and y_0 is too small to bother.

Alternatively, you can add a .qpj file, which includes the EPSG code.

Answer 2

I suggest that you replace the .prj of your shapefile (same name as the other files ) with the prj from Spatial Reference site, which seems to be correct. The difference in X and Y northing comes from the conversion in feet. Probably this is a rounding problem for the two WKT.

PROJCS["NAD83 / California zone 3 (ftUS)",GEOGCS["GCS_North_American_1983",DATUM["D_North_American_1983",SPHEROID["GRS_1980",6378137,298.257222101]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Lambert_Conformal_Conic"],PARAMETER["standard_parallel_1",38.43333333333333],PARAMETER["standard_parallel_2",37.06666666666667],PARAMETER["latitude_of_origin",36.5],PARAMETER["central_meridian",-120.5],PARAMETER["false_easting",6561666.667],PARAMETER["false_northing",1640416.667],UNIT["Foot_US",0.30480060960121924]]