[GRASS-user] dems from coordinate lists

[Hanlie Pretorius]

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