[GRASS-dev] S-JTSK strikes back

[Martin Landa]

Hi Paul,

2007/5/4, Paul Kelly <paul-grass at stjohnspoint.co.uk>:
> OK I think I see now what you are noticing. This seems like a slightly
> different problem again from the one we came across last time. In general
> I think the Krovak support in OGR/PROJ needs completely re-done using
> proj=kocc; it is not enough to keep coming across little issues like this
> and filing bug reports for OGR but anyway let's have a look...

Agree...

[snip]

> > It has picked up at least 0.9999 (lost pseudo_standard_parallel_1 etc).
>
> This goes through two translations here (WKT to GRASS format and back to
> WKT), so is more complicated and I will come back to it later. But note
> that scale_factor =0.9999 is present in the orginal WKT above. I see
> Pseudo Standard Parallel is gone, but again have to ask - is it important
> for the PROJ.4 version of proj=krovak? I really have no idea.

> The WKT description here is just an exact copy of the one you posted at
> the top of the e-mail there and hasn't been processed at all. So no
> surprises that it hasn't changed.
>
> Therefore it seems some information (the pseudo standard parallel value)
> is lost when converting from WKT into GRASS format, and some more
> information (the alpha value) is lost when converting from GRASS format
> back to WKT. Is this important? I don't know anyway how important alpha
> and pseudo standard parallel are. Are they important for proj=krovak or
> does it just ignore it? It seems alpha corresonds to Azimuth in the WKT and
> OSRImportFromProj4() isn't converting it properly, but I really don't know
> how important it is for proj=krovak so wouldn't like to get too deeply
> involved there... Likewise for Pseudo_Standard_Parallel_1 and
> OSRExportToProj4().

Latitude of pseudo standard parallel (78d30m) is hard-coded in
PJ_krovak.c and alpha I guess is ignored.

I see problem using g.proj epsg=2065 -p / -w :

PRIMEM["ferro",-17.666666666668]
PARAMETER["longitude_of_center",24.833333333332], <- not Ferro, but Greenwich
x
pm         : ferro
lon_0      : 42.5 <- OK

Martin

>
> Paul
>
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-- 
Martin Landa <landa.martin at gmail.com> * http://gama.fsv.cvut.cz/~landa *