[GRASS-user] bug in r.proj or just artifact of weird (unrealistic) reprojection ?

[Moritz Lennert]

Hello,

In the course of a course on projections, colleagues of mine have come 
upon an issue in r.proj. I'm not sure if this is a bug, or whether this 
is just due to the fact that they were using data that is not really 
covered in the projection system.

Here's the scenario:

- A location in EPSG 31370 (Belgian Lambert 1972)
- Objectif: project the elevation raster layer from the nc_spm_08 
dataset into that Belgian projection dataset
- A first run of r.proj to get the coordinates of the layer in the new 
projection system. Here's the result:

n=2370907.92051779 s=2378797.24912944 w=-6087464.12326059 
e=-6068211.64408602 rows=1350 cols=1500

As you can see s > n. g.region bails out on that.

But, when you just switch n and s, then everything works fine and the 
elevation dataset gets projected to the correct spot.

Now, I know that this is not the typical reprojection scenario, but I'm 
wondering whether this indicates an underlying issue in r.proj's 
boundary calculation algorithm.

Any ideas ? Should I file a bug ?

Moritz