[GRASS5] difficulties with r.proj

[Andreas Lange]

Hi Carl,

Carl Worth wrote:
> 
> Markus Neteler writes:
>  > On Fri, Oct 26, 2001 at 05:52:58PM -0700, Eric G. Miller wrote:
>  > > I'm guessing you imported your data with r.in.gdal?  Recently there
>  > > have been some changes to fix the problem of not completely defining
>  > > the region when r.in.gdal creates a new location.  You can probably
>  > > fix it by running g.setproj with the correct parameters.  Otherwise,
>  > > please try the new r.in.gdal in CVS.
>  >
>  > a confirmation: Yes, please use the current CVS version. All
>  > others may fail.
> 
> Thanks for your correct diagnosis. I had indeed created my location
> using r.in.gdal.
> 
> I tried to update to the latest cvs, but I didn't see any
> improvement. I updated to the head of the tree using "cvs update -Ad".
> Do I actually want to be on a branch instead?
> 
> I tried to use g.setproj to fix things but it croaked:
> 
>         Would you still like to change some of the parameters (y/n) [n] y
>         Do you want to specify a map datum for this location?(y/n) [n] y
> 
>         Please specify datum name
>         Enter 'list' for the list of available datums
>         Hit RETURN to cancel request
>         >nad27
>         ERROR: invalid input ellipsoid
> 
> The significant thing to notice here is that it never printed the
> current ellipsoid, nor did it prompt for me to change the ellipsoid.

The current g.setproj is a very ugly hack and is planned to be rewritten
in GRASS 5.1. I just introduced the datum stuff without considering that
it may break other things. 
I think the problem you experience is because g.setproj does not allow
to change to a datum with a different ellipsoid (so in fact it does not
allow you to really change the map datum...).
The very short way to change the map datum is to hand-edit the PROJ_INFO
file for a valid datum from $GISBASE/etc/datum.table. But you are on
your own with that. Or you may remove the ellipsoid and datum entries
from the file and re-run g.setproj to update.

Btw. i think GRASS uses clark66, please compare with the
$GISBASE/etc/ellipse.table file.

> 
> By manually creating a location and comparing the PROJ_INFO files I
> could see that many parameters were missing from the one created by
> r.in.gdal. And worse, it had "ellps: clrk66" rather than "ellps:
> clark66". I don't know who's fault that was. But after I changed that
> manually, I was able to get g.setproj to straighten things out for
> me.
> 
> So, it looks like g.setproj needs to be fixed to prompt to change the
> ellipsoid if the current one is invalid.
> 
r.in.gdal needs to be fixed to read the ellipsoid from
$GISBASE/etc/ellipse.table. 

HTH,

Andreas
-- 
Andreas Lange, 65187 Wiesbaden, Germany, Tel. +49 611 807850
url: http://mitglied.tripod.de/AndreasLange
mail: Andreas.Lange_at_Rhein-Main.de - A.C.Lange_at_GMX.net