[GRASS-dev] problems with datum parameters tables

Glynn Clements glynn at gclements.plus.com
Wed Oct 14 09:22:05 EDT 2009

Michael Barton wrote:

> I'm working on the GUI location manager and have run into a couple of  
> irregularities in a couple of the projections parameters files. I'm  
> sending this to the list instead of keeping it in the location wizard  
> track ticket because they are a more general issue that will affect  
> projection/location creation by other means too.
> In proj-parms.table, the entry for "GEOS" is incorrect. There should  
> be 3 subentries for each entry: projection code, projection  
> description, and required parameters. However, GEOS is missing the  
> projection description.
> GEOS:HEIGH=ask,35800000.0;LON0=ask,20.0

Well caught.

> GEOS is the only incorrect formatted entry in the file. It also is NOT  
> in the datums.table file. So either it should be:
> 1) deleted from proj-parms.table, or
> 2) added to datums.table and a descriptive field added in proj- 
> parms.table
> Because it cannot be correctly parsed, I'll just skip it in the GUI  
> location wizard. But if we are going to use this projection, it needs  
> to be corrected in the 2 tables.

The history behind that entry:


IOW, it should probably be there, but should have the right number of
fields (ideally an actual description, but an empty description is
better than invalid syntax).

[I see that this has now been done.]

> Also, in the proj-desc.table, several entries are incorrectly  
> formatted. None of them are used by the proj-parms.table and so they  
> probably should be removed from the proj-desc.table file. All are  
> missing their description fields that are needed so that they can be  
> read by a user. They are:
> GUAM:bool:guam:
> OALPHA:lat:o_alpha:
> OLAT1:lat:o_lat_1:
> OLAT2:lat:o_lat_2:
> OLON1:lon:o_lon_1:
> OLON2:lon:o_lon_2:
> OLONC:lon:o_lon_c:

These are correctly formatted; they just have an empty description.

I removed the data from the g.setproj source code and placed it in
external files. Any descriptions (or lack of them) are as found in the
original g.setproj source code.

If you want to add descriptions, you'll need to examine the PROJ
source code. However, some parameters may have entirely different
meanings for different projections.

Glynn Clements <glynn at gclements.plus.com>

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