[GRASS-user] gps import: definition of WGS84

Moritz Lennert mlennert at club.worldonline.be
Wed Jun 4 10:10:06 EDT 2008

I have finally come around to looking at this issue again...

On Mon, May 26, 2008 05:01, Hamish wrote:
> Moritz Lennert:
> strictly speaking the "projection" (lcc) is there and fine, but (AFAIU)
> the datum transform params for a given datum are left out if there are
> more than one option in the upstream EPSG database. But the +datum= name
> should still be given in that case.
> but I think that is a misdirection: in this case I think QGIS's srs.db is
> broken, missing *all* datum info not just the ambiguos transform params.
> The issue Frank raises still applies, but I do not think it is the main
> problem here.


>> However both of the projections _are_ in the database and
>> QGIS recognizes them.
> but they are incomplete! compare the entry for epsg:31370 in
> /usr/share/proj/epsg and in /usr/share/qgis/resources/srs.sb (using
> sqlitebrowser or such). you will see the srs.db version is missing the
> +towgs84= part. (epsg:31370 is srs:1817 there, or just go to the layers
> proj properties in QGIS and look)

I have been able to solve the problem in QGIS by creating a custom
projection including the transform info (copy-paste of the g.proj -jf
output, replacing  +a and +rf with the relevant +ellps). Now the result
looks fine.

> Could you could create/find the gvSIG report?

Actually, after further investigation, I found that gvSIG allows for
transformations. When you load a file, you can give its projection info.
See [1]. Notice the option to choose a transformation at the bottom (in
this case I chose the EPSG list). You then have a series of choices of
transformations [2]. Or you can chose to go for manual and enter the
transformation parameters yourself [3].

So it's finally only QGIS which has the problem and you can sail around it
by creating a custom projection containing the transformation info.


[1] http://geog-pc40.ulb.ac.be/grass/misc/transformation_gvSIG_1.png
[2] http://geog-pc40.ulb.ac.be/grass/misc/transformation_gvSIG_2.png
[3] http://geog-pc40.ulb.ac.be/grass/misc/transformation_gvSIG_3.png

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