[QGIS-Developer] Issues running Grass r.plane

[Catania, Luke A ERDC-RDE-GRL-VA CIV]

Sylvain,


Thanks.  I did manage to set region in the advanced parameters section.  Changed that and then also realized I had web Mercator as the northing and easting point and geographic extent which put my result out in some other area.  I changed extent to web Mercator and got an good result.


Though when I generate the plane with azimuth of 25 degrees and then run the aspect tool to verify the azimuth that reports 335, which looks like is because r.plane measures in counter clockwise direction where I am used to nort being zero and  then going clockwise.


I would think the coordinate parameter on the plane would be used as a line of bearing and the result would slope up from that which is what I actually need so I need to figure out how to use this tool for my use.


Initially before I found r.plane, I  had found a formula to calculate a constant sloping plane and was using several tools to create what I want but am not getting a correctly sloping plane, so hoping r.plane will work.  I am currently using this formula and the field calculator to create the values in an attribute table and then I rasterize the points using the field value:


height + \
   math.tan(math.radians(slope)) * \
   math.sin(math.radians(aspect)) * longitude + \
   math.tan(math.radians(slope)) * \
   math.cos(math.radians(aspect)) + latitude



Luke







________________________________
From: QGIS-Developer <qgis-developer-bounces at lists.osgeo.org> on behalf of Sylvain POULAIN <sylvain.poulain at giscan.com>
Sent: Sunday, January 31, 2021 2:07 AM
To: QGIS-Developer at lists.osgeo.org
Subject: Re: [QGIS-Developer] Issues running Grass r.plane

Hi Luke,

Setting a region in Grass is really important.
In Grass tools :
- there is a panel tab where you can adjust region named "Region",
- you can also use g.region.multiple.raster from module tab,
- a shell is present in module tab to use grass commands.

In processing toolbox, setting region is embedded in tool.

Regards,

Sylvain POULAIN

Le sam. 30 janv. 2021 à 04:30, Catania, Luke A ERDC-RDE-GRL-VA CIV <Luke.A.Catania at erdc.dren.mil<mailto:Luke.A.Catania at erdc.dren.mil>> a écrit :
Looking to use r.plane to create a slope of a constant plane.

Tried to run the Grass tool using the example in the help below , but in QGIS I do not see a g.region method so how do I limit my area?

# set computational region
g.region raster=elev_lid792_1m -p

# get center coordinates as an example
g.region -c
# get terrain height at point
r.what map=elev_lid792_1m coordinates=638650.0,220375.0
# shows elevation: 116.7734

# generate tilted plane
r.plane myplane30 dip=30 az=75 east=638650.0 north=220375.0 \
        elev=116.7734 type=FCELL

Whe running it with the example input.

r.plane sloping_plane dip=30 az=75 east=638650.0 north=220375.0 elev=116.7734 type=FCELL

I just get a constant plane of the same height throughout, so not sure of that is an issue of not setting the region.

Luke
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