[GRASS-user] dems from coordinate lists

[MS]

If I follow correctly, instead of v.to.rast, you need to interpolate a  
raster DEM from the points.   v.surf.rst produces nice results, but  
there are other interpolation modules as well in the raster category.

Best regards,

Mark

On May 13, 2010, at 10:26 AM, Hanlie Pretorius <hanlie.pretorius at gmail.com 
 > wrote:

> Hi,
>
> I've obtained DEMs in text files with columns X, Y and Z at 25m
> spacing. The first three entries in the text file are:
>
> -----
> X,Y,Z
> 99550,2.9883e+06,1473.47
> 99550,2.98828e+06,1473.57
> 99550,2.98825e+06,1473.63
> -----
>
> To me it seems the easiest way to import these is the following:
>
> 1. v.in.ascii
>
> 2. Set the region to the extents of new vector file and the  
> resolution to 25m.
>
> 3. v.to.rast.
>
>
> This 'works' but I get horizontal strips of no data in my raster DEM
> at 25m spacings.
>
> Also, when I look at the raster and the vector layer together, the
> vector points are not always on the edges of the raster cells.
>
> Can someone perhaps help me to fix this?
>
> g.region:
>
> projection: 99 (Transverse Mercator)
> zone:       0
> datum:      ** unknown (default: WGS84) **
> ellipsoid:  wgs84
> north:      2988300
> south:      2959850
> west:       74300
> east:       99550
> nsres:      25
> ewres:      25
> rows:       1138
> cols:       1010
> cells:      1149380
>
> v.info:
> +-- 
> --- 
> --- 
> --------------------------------------------------------------------+
> | Layer:           dem_2628cc_25m at C83
> | Mapset:          C83
> | Location:        sa_tm_19deg_E
> | Database:        C:\Hanlie\grassdata
> | Title:
> | Map scale:       1:1
> | Map format:      native
> | Name of creator: Administrator
> | Organization:
> | Source date:     Thu May 13 16:06:07 2010
> |-- 
> --- 
> --- 
> --------------------------------------------------------------------|
> |   Type of Map:  vector (level: 2)
> |
> |   Number of points:       1151529         Number of areas:      0
> |   Number of lines:        0               Number of islands:    0
> |   Number of boundaries:   0               Number of faces:      0
> |   Number of centroids:    0               Number of kernels:    0
> |
> |   Map is 3D:              Yes
> |   Number of dblinks:      0
> |
> |         Projection: Transverse Mercator
> |               N:           2988300    S:           2959850
> |               E:             99550    W:             74300
> |               B:           1429.79    T:            1740.2
> |
> |   Digitization threshold: 0
> |   Comments:
> |
> +-- 
> --- 
> --- 
> --------------------------------------------------------------------+
>
> r.info:
>
> +-- 
> --- 
> --- 
> --------------------------------------------------------------------+
> | Layer:    dem_2628cc_25m at C83             Date: Thu May 13 16:15:50  
> 2010
> | Mapset:   C83                            Login of Creator:  
> Administrator
> | Location: sa_tm_19deg_E
> | DataBase: C:\Hanlie\grassdata
> | Title:    Categories ( dem_2628cc_25m )
> | Timestamp: none
> |-- 
> --- 
> --- 
> --------------------------------------------------------------------|
> |   
>     
>     
>                                                                     |
> |   Type of Map:  raster               Number of Categories: 0
> |   Data Type:    DCELL
> |   Rows:         1138
> |   Columns:      1010
> |   Total Cells:  1149380
> |        Projection: Transverse Mercator
> |            N:    2988300    S:    2959850   Res:    25
> |            E:      99550    W:      74300   Res:    25
> |   Range of data:    min = 1429.850000  max = 1739.410000
> |
> |   Data Source:
> |    Vector Map: dem_2628cc_25m at C83 in mapset C83
> |    Original scale from vector map: 1:1
> |
> |   Data Description:
> |    generated by v.to.rast
> |
> |   Comments:
> |    v.to.rast input="dem_2628cc_25m at C83" output="dem_2628cc_25m"  
> use="z"\
> |     type="point,line,area" layer=1 value=1 rows=4096
> |
> +-- 
> --- 
> --- 
> --------------------------------------------------------------------+
>
> Thanks
> Hanlie
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