[GRASS-user] Creating raster from imported vector data

Michael Perdue michael_perdue at yahoo.ca
Tue Sep 26 22:59:58 EDT 2006

Are you sure that you input data is cartesian (ie XY unprojected) and  
not Geographic (lat/long which is also unprojected). It would be very  
unusual to have unprojected vector data in a cartesian coordinate  
I think that what has happened is that you coordinates are in lat/ 
long which would cause all your data to be bunched up in a tiny  
little space as the min/max for lat/long is +90 to -90 and +180 to  
-180 respectively.



On 26-Sep-06, at 4:56 PM, mort wrote:

> Hi All,
> I'm new user of Grass and I try to convert my Mapinfo tab files  
> into Grass raster slope map.
> The oryginal files were non-earth projection (kilometre grid) with  
> isolines stored in column "wysokosci_m".
> I've created the new location: XY (unprojected) with nsres=7000 and  
> weres=5000, I've imported data into wysokosci2 vector layer:
> GRASS 6.0.1 (nowa):~/grass/GRASSDATA > v.info -c wysokosci2
> Displaying column type for database connection of layer 1:
> In accordance to this book: http://www.gdf-hannover.de/lit_html/ 
> grass60_v1.2_en/node64.html
> I tried to convert isolines directly to surface using v.surf.rst:
> v.surf.rst input=wysokosci2 layer=1 zcolumn=wysokosc_m  
> dmax=1000.000000 dmin= 825.000000 slope=slope2 zmult=1.0  
> tension=40. smooth=0.1 segmax=40 npmin=200
> and I get:
> Warning: there are points outside specified region--ignored 128 points
> Warning: ignoring 27375 points -- too dense
> WARNING: 39 points given for interpolation (after thinning) is less  
> than given NPMIN=200
> Warning : there is less than 400 points for interpolation, no  
> segmentation is necessary, to run the program faster, set  
> segmax=400 (see manual)
> Loading data from attribute table ...
> The number of points from vector file is 27542
> The number of points outside of region 128
> The number of points being used is 39
> The output raster is one big yellow  square.I've also tried to  
> decrease the dmin but, in this case:
> Points are too concentrated -- please increase DMIN
> I'm not sure where I made mistake. I would be very thankfull for  
> any help or maybe existing guide,
> Mort
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