On Mon, 17 May 2010, Maciej Sieczka wrote:
GRASS already has the correct parameters for Poland. The problem is
that it doesn't recognise the datum name "Pulkovo_1942_58"; it is
looking for "Pulkovo_1942". I would recommend the patch below for
working around this problem.
Index: lib/proj/convert.c
===================================================================
--- lib/proj/convert.c (revision 42262) +++ lib/proj/convert.c
(working copy) @@ -744,6 +744,8 @@ "Militar_Geographische_Institut",
"Potsdam_Datum_83", "Deutsches_Hauptdreiecksnetz", +
"Pulkovo_1942_58", + "Pulkovo_1942", NULL };
Does the trick for location wizard at GRASS startup (e.g. for epsg 2174
a nice selection GUI pops up) and the resulting PROJ_INFO as well as
`g.proj -p' output are OK, but `g.proj -p epsg=2174' on the command line
still fails to include the towgs84 parameter set at all, so does `g.proj
-c epsg=2174'.
It does include the datum though (there is a line "datum: S-42"), which
means that the default GRASS parameters for S-42 (over the whole region it
is used in) will be used where necessary (e.g. in g.proj -jf epsg=2174). I
think this is the best we can hope for for now; in GRASS versions
6.2.1 and earlier g.proj when used on the command-line used to
interactively prompt for the user to select a datum transformation if the
datum was not fully specified, but this behaviour had to be removed when
we were working towards removing all command-line interaction from modules
so they could be used in scripts with no side-effects. Since GRASS 6.2.2
if you want g.proj to give you a choice of datum transformation parameters
(when one is available), you have to add "datumtrans=-1" to the
command-line; this is what the location creation GUIs do to determine the
available sets of datum transformation parameters.
Does this sound acceptable for now - in particular are there any
differences between Pulkovo 1942 and Pulkovo 1942 (58) that are worth
worrying about?
I don't know.
OK well I will guess that any differences are not relevant for us here,
and will see about adding the equivalence of Pulkovo_1942_58 and
Pulkovo_1942 to SVN.
Paul
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