[GRASS-dev] creating new location in krovak projection

[Paul Kelly]

On Wed, 6 Dec 2006, Jachym Cepicky wrote:

> hi Paul,
>
> On Tue, Dec 05, 2006 at 10:32:40AM +0000, Paul Kelly wrote:
>> Hello Jachym
>> Those datum paramters are already in GRASS (and have been for several
>> years). The datum short name is hermannskogel, not that obvious and a bit
>> long, and not my choice but we can't change it now.
>>
>> Interestingly the Slovak parameters are (very slightly) different from my
>> source - they must cover a slightly different part of the country or have a
>> different accuracy or something. This would need to be confirmed and
>> documented before adding them to the file. Hopefully the site you got them
>> from has some information?
>>
>> Paul
>
> these parameters are from Radim's old GRASS-Krovak page, we have just
> copied those parameters from that page to our wiki.

Oh OK. ISTR Radim did some detailed comparisons of datum shift errors 
using different parameters and produced some nice maps showing the 
distortion. It would definitely be worthwhile checking that out and why 
the parameters I got from that European co-ordinate conversion site are 
different, if anybody has time.

> This means, that we are all adding towgs84 parameter by hand since many
> years, while we just could add hermannskogel datum :-( That is life.
>
> Anyway, do you think, patch for
>
> general/g.setproj/proj-parms.table
>
> is ok and can be applyed? It worked for me and for Martin, how desired.

Yes, please go ahead - I have not followed the recent modifications to 
g.setproj in much depth but it seems obvious to do.

>
>
> Howto setup Location with Krovak projection could look like follows:
>
> 1 - Press "d" for "Other Projection"
> 2 - Specify "krovak" for projection name
> 3 - Press "y", that you want to specify gedetic datum for this location
> 4 - Choose "hermannskogel" from list of datum names
> 5 - Choose "2" for Czech republic or 3 for Slovak republic from list of
>    avaliable parameter sets
> 6 - Plural form of units: meters
> 7 - Specify default region for your location
>
> Does this look ok?

Yes that's right.

Paul