Re: r.slope.aspect with -n flag giving aspect of flat areas as -9998

Hi Anna and Markus,

Thank you very much!

A filled a ticket: https://github.com/OSGeo/grass/issues/319

Best regards,
Pedro



Markus Metz <[email protected]> escreveu no dia quinta,
30/01/2020 à(s) 08:26:

>
>
> On Tue, Jan 28, 2020 at 12:50 PM Pedro Venâncio <[email protected]>
> wrote:
> >
> > Hi all,
> >
> > I was testing r.slope.aspect with the "new" -n flag, also to include -e
> and -n flags in QGIS Processing, but -n flag is giving aspect values of
> flat areas as -9998, instead of -9999, when the precision choosed is CELL,
> and the output data type is CELL.
>
> that seems to be a rounding error, even though float or double should be
> able to represent -9999 exactly. Should be easy to fix.
>
> Markus M
> >
> > https://grass.osgeo.org/grass78/manuals/r.slope.aspect.html
> >
> > I've tested with GRASS 7.6 (on Linux) and GRASS 7.8.2 (on Windows), both
> in the GUI and CLI.
> >
> > (Tue Jan 28 11:19:40 2020)
>
> > r.slope.aspect -e -n --verbose elevation=SRTM_PT_25m@PERMANENT
> slope=SRTM_PT_25m_Slope_Deg_GRASS aspect=SRTM_PT_25m_Aspect_Std_GRASS
> precision=CELL
> > Percent complete...
> > Elevation products for mapset <PERMANENT> in <SRTM_PT_25m>
> > Min computed aspect 0.0000, max computed aspect 360.0000
> > Aspect raster map <SRTM_PT_25m_Aspect_Std_GRASS> complete
> > Min computed slope 0.0000, max computed slope 75.2970
> > Slope raster map <SRTM_PT_25m_Slope_Deg_GRASS> complete
> > (Tue Jan 28 11:20:24 2020) Comando terminado (43 sec)
> >
> > r.info map=SRTM_PT_25m_Aspect_Std_GRASS@PERMANENT
>
> >
>  +----------------------------------------------------------------------------+
> >  | Map:      SRTM_PT_25m_Aspect_Std_GRASS@  Date: Tue Jan 28 11:20:24
> 2020    |
> >  | Mapset:   PERMANENT                      Login of Creator:
> PedroVenancio   |
> >  | Location: SRTM_PT_25m
>      |
> >  | DataBase: D:\ICNF\Modelos_Combustivel_2018\Landscape_File\grass78
>      |
> >  | Title:    Aspect counterclockwise in degrees from east
>       |
> >  | Timestamp: none
>      |
> >
>  |----------------------------------------------------------------------------|
> >  |
>      |
> >  |   Type of Map:  raster               Number of Categories: 360
>       |
> >  |   Data Type:    CELL
>       |
> >  |   Rows:         23200
>      |
> >  |   Columns:      11360
>      |
> >  |   Total Cells:  263552000
>      |
> >  |        Projection: ETRS89 / Portugal TM06
>      |
> >  |            N:     278000    S:    -302000   Res:    25
>       |
> >  |            E:     164000    W:    -120000   Res:    25
>       |
> >  |   Range of data:    min = -9998  max = 360
>       |
> >  |
>      |
> >  |   Data Source:
>       |
> >  |    raster elevation file SRTM_PT_25m@PERMANENT
>       |
> >  |
>      |
> >  |
>      |
> >  |   Data Description:
>      |
> >  |    generated by r.slope.aspect
>       |
> >  |
>      |
> >  |   Comments:
>      |
> >  |    aspect map elev = SRTM_PT_25m@PERMANENT
>       |
> >  |    zfactor = 1.00
>      |
> >  |    min_slope = 0.000000
>      |
> >  |
>      |
> >  |    r.slope.aspect --verbose -e -n elevation="SRTM_PT_25m@PERMANENT"
> slo\   |
> >  |    pe="SRTM_PT_25m_Slope_Deg_GRASS"
> aspect="SRTM_PT_25m_Aspect_Std_GRAS\   |
> >  |    S" format="degrees" precision="CELL" zscale=1.0 min_slope=0.0
>       |
> >  |
>      |
> >
>  +----------------------------------------------------------------------------+
> > (Tue Jan 28 11:26:09 2020) Comando terminado (0 sec)
>
> >
> >
> > Using the default precision as FCELL, all goes ok:
> >
> > (Tue Jan 28 11:33:08 2020)
>
> > r.slope.aspect -e -n --verbose elevation=SRTM_PT_25m@PERMANENT
> slope=SRTM_PT_25m_Slope_Deg_GRASS_2 aspect=SRTM_PT_25m_Aspect_Std_GRASS_2
> > Percent complete...
> > Elevation products for mapset <PERMANENT> in <SRTM_PT_25m>
> > Min computed aspect 0.0000, max computed aspect 359.8096
> > Aspect raster map <SRTM_PT_25m_Aspect_Std_GRASS_2> complete
> > Min computed slope 0.0000, max computed slope 75.2970
> > Slope raster map <SRTM_PT_25m_Slope_Deg_GRASS_2> complete
> > (Tue Jan 28 11:34:01 2020) Comando terminado (53 sec)
> >
> > (Tue Jan 28 11:34:27 2020)
>
> > r.info map=SRTM_PT_25m_Aspect_Std_GRASS_2@PERMANENT
>
> >
>  +----------------------------------------------------------------------------+
> >  | Map:      SRTM_PT_25m_Aspect_Std_GRASS_  Date: Tue Jan 28 11:34:01
> 2020    |
> >  | Mapset:   PERMANENT                      Login of Creator:
> PedroVenancio   |
> >  | Location: SRTM_PT_25m
>      |
> >  | DataBase: D:\ICNF\Modelos_Combustivel_2018\Landscape_File\grass78
>      |
> >  | Title:    Aspect counterclockwise in degrees from east
>       |
> >  | Timestamp: none
>      |
> >
>  |----------------------------------------------------------------------------|
> >  |
>      |
> >  |   Type of Map:  raster               Number of Categories: 360
>       |
> >  |   Data Type:    FCELL
>      |
> >  |   Rows:         23200
>      |
> >  |   Columns:      11360
>      |
> >  |   Total Cells:  263552000
>      |
> >  |        Projection: ETRS89 / Portugal TM06
>      |
> >  |            N:     278000    S:    -302000   Res:    25
>       |
> >  |            E:     164000    W:    -120000   Res:    25
>       |
> >  |   Range of data:    min = -9999  max = 359.8097
>      |
> >  |
>      |
> >  |   Data Source:
>       |
> >  |    raster elevation file SRTM_PT_25m@PERMANENT
>       |
> >  |
>      |
> >  |
>      |
> >  |   Data Description:
>      |
> >  |    generated by r.slope.aspect
>       |
> >  |
>      |
> >  |   Comments:
>      |
> >  |    aspect map elev = SRTM_PT_25m@PERMANENT
>       |
> >  |    zfactor = 1.00
>      |
> >  |    min_slope = 0.000000
>      |
> >  |
>      |
> >  |    r.slope.aspect --verbose -e -n elevation="SRTM_PT_25m@PERMANENT"
> slo\   |
> >  |    pe="SRTM_PT_25m_Slope_Deg_GRASS_2"
> aspect="SRTM_PT_25m_Aspect_Std_GR\   |
> >  |    ASS_2" format="degrees" precision="FCELL" zscale=1.0 min_slope=0.0
>      |
> >  |
>      |
> >
>  +----------------------------------------------------------------------------+
> > (Tue Jan 28 11:34:28 2020) Comando terminado (0 sec)
> >
> >
> > The elevation map I'm using is this one:
> > https://www.fc.up.pt/pessoas/jagoncal/srtm/SRTM_PT_25m.tif
> >
> > As CELL is a 32 bit integer with a range from -2,147,483,647 to
> +2,147,483,647, -9999 should be fine to conform inside it.
> >
> > Another issue I see is in r.info, that is showing the title as
> >
> > | Title:    Aspect counterclockwise in degrees from east
> >
> > which is not correct in this case, as the -n flag was used.
> >
> > Could these be bugs?
> >
> > Thank you very much.
> >
> > Best regards,
> > Pedro Venâncio
> > _______________________________________________
> > grass-dev mailing list
> > [email protected]
> > https://lists.osgeo.org/mailman/listinfo/grass-dev
>

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