[GRASS-user] adding a datum to the GRASS database

[Ali Swanson]

Hi Markus -
Thanks for your prompt reply.  Unfortunately, I think that my GRASS skills
are faaaar below those of most other users. (I don't even know how to
*find* the datum.table file to which I thought I was supposed to add the
ARC1960 datum, or really understand your suggestions.) But! From your
advice I was able to (I think) select the proper Arc1960 datum.  I have
done everything so far with the graphical interface, and was trying to
select the Arc1960 (using location wizard) from the first menu choice
(selecting from a list of coordinate system parameters) -- when I chose the
second menu option (select EPGS code of spatial reference system), I
believe I found it.  Pretty basic, in the end.  Thanks again!




On Sat, Nov 17, 2012 at 5:54 AM, Markus Neteler <neteler at osgeo.org> wrote:

> Hi Ali,
>
> On Fri, Nov 16, 2012 at 9:05 PM, Ali Swanson <swanson.ali at gmail.com>
> wrote:
> > Hi all -
> > I'm brand new to GRASS (though have basic familiarity with ArcInfo).
>
> welcome :)
>
> > I work
> > in a datum that apparently isn't contained in the basic GRASS library --
> > from what I've uncovered searching this list & the general web, I need to
> > add my datum by going to the $GISBASE/etc/datum.table and appending this
> > text:
> >
> > The Arc 1960 datum; source: EPSG database
> > arc60 "Arc 1960" clark80 dx=-160 dy=-6 dz=-302
>
> Which EPSG code is that? EPSG 4210, this one?
>
> epsg_tr -pretty_wkt 4210
> GEOGCS["Arc 1960",
>     DATUM["Arc_1960",
>         SPHEROID["Clarke 1880 (RGS)",6378249.145,293.465,
>             AUTHORITY["EPSG","7012"]],
>         TOWGS84[-160,-6,-302,0,0,0,0],
>         AUTHORITY["EPSG","6210"]],
>     PRIMEM["Greenwich",0,
>         AUTHORITY["EPSG","8901"]],
>     UNIT["degree",0.0174532925199433,
>         AUTHORITY["EPSG","9122"]],
>     AUTHORITY["EPSG","4210"]]
>
> It should be there. You can use the Location Wizard to select this
> EPSG code.
>
> BUT: I just tried and the datum is not recognised:
>
> g.proj -w
> GEOGCS["clark80",
>     DATUM["unknown",
>         SPHEROID["Clarke_1880",6378249.145,293.465]],
>     PRIMEM["Greenwich",0],
>     UNIT["degree",0.0174532925199433]]
>
> Do these tickets strike back?
> http://trac.osgeo.org/grass/ticket/1452
> http://trac.osgeo.org/grass/ticket/1748
>
> Markus
>
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