[Gvsig_english] QUESTION gvSIG 1.9 (BN 1253) -- Establish aspect and slope of an area based on contour lines?

[Francisco José Peñarrubia]

Hi Simon.

The answer is yes, you can (Obama joke) ;-)

You will use Sextante tools + Geoprocess tool.

This is a short summary:

1.- Rasterize your contours shape. Sextante -> Rasterization and 
interpolation -> Rasterize Vectorial layers. Choose the field name that 
contains Elevation data. Remember to choose a good extent and a suitable 
cell size.
2.- Now, time to interpolate. And easy method (you can also choose 
Krigging, but probable is enough with Sextante -> Basic tools por raster 
layers -> Void filling
3.- If you need slope, use Sextante -> Geomorphometry and terrain analysis

After that, you will have an MDT and a slope raster. The next steps are 
to crop this MDT with your polygon layer (parcels, for example), convert 
this raster to points and assign average slope or altitude to this polygons.

4.- Sextante-> Basic tools for raster layers -> Crop grid with polygon layer
5.- Sextante -> Vectorization -> Raster layer to points layer.
6.- View -> Geoprocess toolbox -> Analysis -> Spatial join => choose 
input cover your polygon layer and clip cover you point layer (I know, 
the name are confusing the user...). When you click in OK, a window 
appears. Choose slope or altitude and click in central button. Choose 
average. Then click yes to the questions and you should have a polygon 
layer with average slope or altitude, depending on wich raster layer you 
choose (MDT or slope).

Hope it helps.

Best regards.

Fran Peñarrubia
www.scolab.es

PS: (Excerpt from ENOSAT course :-) ).

Simon Cropper escribió:
> Hi,
>
> I have a shapefile showing contours across a region.
>
> Visual inspection of the vector data suggests that various subregions 
> have different aspects/bearings and slope.
>
> Is there a way using gvSIG or any of its plugins to visualize or 
> categorize this data?
>
> My desired output would be a polygon file with the attribute field 
> aspect/bearing and slope.
>
> -- 
>
> Cheers Simon
>
> Simon Cropper
> Botanicus Australia Pty Ltd
> PO Box 160, Sunshine, Victoria 3020.
> P: 9311 5822. M: 041 830 3437.
> mailto: scropper at botanicusaustralia.com.au 
> <mailto:scropper at botanicusaustralia.com.au>
> web: www.botanicusaustralia.com.au <http://www.botanicusaustralia.com.au>
>
>
>
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