[gdal-dev] Unable to create OGRSpatialReference

[jcurru]

Hello!

I have an old problem with TOWGS84 and OGRSpatialReference. Most likely it's
because I'm no expert in GDAL. It is important for my project, and limits
many of its capabilities. The fact is that, for unknown reasons (to me),
proj4 does not do well conversions between coordinate system if there are
not a TOWGS84 nodes inside the OGRSpatialReference(s).

First of all: is this so? Do I really need that node? If not properly added,
clearly some conversions fail.

I continue: Imagine getting an OGRSpatialReference a shapefile or a TIF. To
assign the node TOWGS84, what I do is look into the file "EPSG", found in
many sites related to GDAL, that contains a list of EPSGs with corresponding
parameters. Knowing the EPSG, I can generate the TOWGS84 node smoothly.

The problem comes when I do not know the OGRSpatialReference’s EPSG,
something very common: AutoIdentifyEPSG () gets nothing most of the time, at
least with the systems in which I work.

So what to do then? I need the TOWGS84 node but, with my knowledge, I can
only get it from the EPSG.

Many thanks in advance.




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