[R-sig-Geo] CRS: list of datum?

[Tom Gottfried]

I'm really not an expert, but I know that in GRASS exist four different sets of +towgs84 parameters 
for the potsdam datum (due to regional differences that seem to go back to inaccuracies in the 
original land survey by Karl Friedrich Gauß in Germany). If one of these is specified, it is not 
necessary to specify +datum=potsdam, as all of the information seems to be in +towgs84. So if you 
have the +towgs84 parameter set for the datum you need, I would think you can just specify that. 
What you can read here seems to approve this:

http://trac.osgeo.org/proj/wiki/GenParms#towgs84-DatumtransformationtoWGS84

Tom

Am 11.10.2010 16:28, schrieb Agustin Lobo:
> Thanks,
>
> I see the problem: have 11 datums and ED50 or ED87 are not
> among them. Is there any way to add datums? or is this something that
> comes with proj4 and it is just as it is?
>
> Agus
>
>
> 2010/10/11 Tom Gottfried<tom.gottfried at wzw.tum.de>:
>> Hi Agustin,
>>
>> you can use `cs2cs -ld' directly in your shell to list all datums known to
>> proj.4
>>
>> Tom
>> --
>> Technische Universität München
>> Department für Pflanzenwissenschaften
>> Lehrstuhl für Grünlandlehre
>> Alte Akademie 12
>> 85350 Freising / Germany
>> Phone: ++49 (0)8161 715324
>> Fax:   ++49 (0)8161 713243
>> email: tom.gottfried at wzw.tum.de
>> http://www.wzw.tum.de/gruenland
>>
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-- 
Technische Universität München
Department für Pflanzenwissenschaften
Lehrstuhl für Grünlandlehre
Alte Akademie 12
85350 Freising / Germany
Phone: ++49 (0)8161 715324
Fax:   ++49 (0)8161 713243
email: tom.gottfried at wzw.tum.de
http://www.wzw.tum.de/gruenland