Re: importing a grid into a GRASS raster in GRASS tools

On 10/25/06, mariate-WTyz0/b0UGisx2OscRBu2odd74u8MsAO@xxxxxxxxxxxxxxxx 
<mariate-WTyz0/b0UGisx2OscRBu2odd74u8MsAO@xxxxxxxxxxxxxxxx> wrote:
> Hi QGISers:
>
> I am observing some behaviors and I'd like to know if this is what one should
> expect, if I am doing anything wrong, or if things need some fixing:
>
> 1- I am using QGIS 0.8 (preview 1) (because with preview 2, I am not able to
> use the GRASS shell under the GRASS tools menu). My platform is Windows 2000.

This was already discussed in the list and I think that Stephan
forgot to add msys into the package, I am not sure if it was later
added to the package, you can just copy
 m.ico msys.bat msys.ico bin/ etc/
from msys to your QGIS dir and it should work.

> 2- I have a DEM in binary grid format in the QGIS project. The grid is in State
> Plane Coord system (Lambert comformal conic), MAssachusetts Mainland NAD 83 in
> meters, but when I bring it into QGIS, I need to redefine its projection,
> because aparently QGIS doesn't read it and assign it automatically. Is this
> always going to be the case?
>
> 3-I define the projection of the grid, and I define the projection of the QGIS
> project. I create a new GRASS mapset with the same coordinate information.
> Then, I proceed to "IMPORT" the grid into a GRASS raster, using the "IMPORT
> GDAL RASTER LAYER" in the GRASS tools. While it is importing, I get this
> message:
>
> "Warning 4: Unable to find state plane zone in stateplane.csv,
> likely because the GDAL data files cannot be found. Using
> incomplete definition of state plane zone.
>
> Over-riding projection check.
> Proceeding with import... "
>
> But when I look into the stateplane.csv file,
>
> line 44 has that info: 2001, MASSACHUSETTS, MAINLAND, 2, NAD83, 2001, 26986
> ????

It could be that it cannot even find the stateplane.csv, I am not sure.
Please fill this as a new ticket in bugtracker.

> 4- Because the projection of the grid and the mapset are the same, in this case
> this is not a big problem, but if they were different, the GDAL import feature
> by default OVER-RIDES the projection to match it to the map set, so then, we
> would get a GRASS raster with wrongly defined projection, right?

Yes. I have used the -o flag in GRASS tools for r.in.gdal and v.i.ogr
because my experience is that it always fails even if both projections
are identical. So this way people get ate least something.
The correct way to import a raster with different projection to GRASS
is to create a new location for rasters projection, import there
and then reproject with r.proj.

Note also that raster layers are not reprojected on-the- fly in 0.8.

> 5-After the import, I hit "view output". A raster gets added to the view, but
> it is all black. If I right click in properties, I don't see max/min value, but
> if I look at the raster properties in the "GRASS tools browser", I see that all
> the parameters of the raster seem to be correct, so I recover hopes and I go to
> GRASS tools and set a "raster color map". Then, it does not change
> automatically, and I have to fo to view> refresh. May be I am expecting too
> much, but what would be nice is that when I try to "view the output" in the
> first place, a random color map gets assigned to the newly imported raster, so
> the user doesn't panic seeing it all black. But if a raster map needs to be
> created, could it be automatically refreshed? That by itself would be a nice
> feature.

The color table could either be assigned by r.in.gdal, but that is pure
GRASS issue (i.e. should go to GRASS list) or QGIS could assign
some table if no one is defined. You can fill a new ticket as request.

Regarding auto redraw after r.colors i am not sure if it is good idea
but you can also fill a new ticket.

> Sorry for this long message, I dont want to be a pain. These may be details but
> make the experience of beginners and students harder, and I submit them here in
> case they are easy to fix or implement. I dont know if those behaviors are
> normal or bugs.

Thanks, we need such feedback.

> 6-ALSO: if anybody has some write up of how to use the "RASTER MAP CALCULATOR"
> in the GRASS tools, I will very much appreciate it. I haven't got it to work.
> It does not see the rasters I have open, for example...

Right, that was bug and that is fixed but probably after preview 2,
release. For now you can use constants and functions however.

Radim

> Thanks!, Maria F.
>
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