[OSGeo Africa] QGIS and projection names

Hanlie Pretorius bloupanda at gmail.com
Thu Apr 17 05:03:12 PDT 2014


I created a shapefile in QGIS and selected South African CRS:
HBK_NO_23 as my CRS.

When I open the file in QGIS, the metadata for the projection reads:

USER:100001 -  * Generated CRS (+proj=tmerc +lat_0=0 +lon_0=23 +k=1
+x_0=0 +y_0=0 +ellps=WGS84 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs)

Furthermore, this 'user specified' CRS now exists in my list of
projections. I find this rather annoying because I end up with a
growing list of identical projection definitions.

The .prj file reads:


and the .qpj file reads:


I'm just wondering if all these different CRS specifications may be
causing problems when using the shapefile with other programs, such as
ArcGIS. I am having problems with shapefiles looking correct in QGIS
but shifted in ArcGIS. The shift is about 70 meters in the x direction
and 255 meters in the y direction.

I found this web page (http://www.georeference.org/forum/t115330)
saying that the difference between WGS84 and Hartbeeshoek 1994) is
approximately 0.2 m and 0.3 m in Lo y and x coordinates respectively.

I see in ArcGIS the transformation reads dx=0, dy=0, dz=0. So if the
two datums are identical for most purposes, what else could be causing
a shift in positions between the two programs?


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