[GRASS-user] reprojection from/to gnomonic projection two years later

[Milan Salek]

Hello,

I am referring to the reprojection problem of GRASS6.x described here:
http://www.intevation.de/rt/webrt?display=History&serial_num=3630

To sum up, the GRASS version 5.3+ (i.e., the current version 6.2, too; I'v not
tested CVS version) incorrectly reprojects the maps between coordinate system
using gnomonic projection (using only sphere as a reference body) and any other
coordinate system with projection using ellipsoid. There is obvious erroneous
north-south shift of approx 0.19 degree (at 50 deg latitude), very likely due to
the different reference body (and mayby because of  the mix of of
geodetic/geometric latitude - ?).

The system proj (http://proj.maptools.org/) works OK, there is not a problem.

The old [vr].proj in GRASS 5.0.3 is reprojecting perfectly, without any shift,
obviously handling the reference body correctly. I think that there could be
some possibility to fix the problem if this old version works OK. Maybe the
problem could have been connected with the introduction of the datum
transformation function in grass5.3 (http://grass.itc.it/devel/roadmap.php).

I would like to ask if there is a possibility to fix the shortcoming.
As a workaround, I still have to maintain the old version of GRASS 5.0.3 at one
computer just for the reprojections using gnomonic projection. For some
reprojection tasks I have available external programs, but the correction of the
above mentioned error would be very helpful. If the correction of the error (or
feature?) :o) is not planned in the future, let me know, too, please.

BTW, is anywhere a repository of old GRASS 5.0.3 for cygwin? I'v found only
GRASS 5.4.

Thanks in advance for any response.

Milan Salek

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