[GRASS-user] v.to.rast gives empty raster layer

[Micha Silver]

On 05/03/2011 09:11 AM, Hanlie Pretorius wrote:

> Hi Maris,
>
> Thanks, your suggestion worked. With the region's resolution set to
> 5m, I got some output.
>

Hi Maris:
Sorry for butting in on this, but I don't understand why the region 
resolution should make any difference to v.to.rast??
Would you mind to explain?
Thanks,
Micha

> Regards
> Hanlie
>
> 2011/5/2, Maris Nartiss<maris.gis at gmail.com>:
>> g.region vect=contours_20m
>>
>> Also 20x20m cells wouldn't be too large?!?
>>
>> Maris.
>>
>>
>> 2011/5/2, Hanlie Pretorius<hanlie.pretorius at gmail.com>:
>>> Hi,
>>>
>>> I'm working in GRASS 6.4.1 on Windows XP.
>>>
>>> I want to use r.surf.contour to convert contour lines into a DEM.
>>> However, I first need to convert my vector contour lines into raster
>>> contour lines. My region is set to the contours_20m vector layer, with
>>> a 20m resolution.
>>>
>>> v.to.rast --overwrite input=contours_20m output=contours_20m use=attr
>>> column=HEIGHT
>>> Loading data...
>>> Reading features...
>>> Writing raster map...
>>> Converted areas: 0 of 0
>>> Converted points/lines: 1593 of 1593
>>> v.to.rast complete.
>>>
>>> r.info for the result is:
>>>   | Layer:    contours_20m at CDNGI_DEM         Date: Mon May 02 14:18:00 2011
>>>   | Mapset:   CDNGI_DEM                      Login of Creator: hanlie
>>>   | Location: SA_Lo_29E
>>>   | DataBase: F:\grassdata
>>>   | Title:    Labels ( contours_20m at CDNGI_DEM )
>>>   | Timestamp: none
>>> |----------------------------------------------------------------------------
>>>   |
>>>   |   Type of Map:  raster               Number of Categories: 0
>>>   |   Data Type:    DCELL
>>>   |   Rows:         1772
>>>   |   Columns:      1750
>>>   |   Total Cells:  3101000
>>>   |        Projection: Transverse Mercator
>>>   |            N: -3121229.69982072    S: -3156672.30728643   Res:
>>> 20.00147148
>>>   |            E: -32474.90929218    W: -67483.27873573   Res: 20.00478254
>>>   |   Range of data:    min = 1620  max = 2460
>>>
>>>   |   Data Source:
>>>   |    Vector Map: contours_20m at CDNGI_DEM in mapset CDNGI_DEM
>>>   |    Original scale from vector map: 1:1
>>>   |
>>>   |   Data Description:
>>>   |    generated by v.to.rast
>>>   |
>>>   |   Comments:
>>>   |    v.to.rast input="contours_20m at CDNGI_DEM" layer=1
>>> type="point,line,ar\
>>>   |    ea" output="contours_20m at CDNGI_DEM" use="attr" column="HEIGHT"
>>> value\
>>>   |    =1 rows=4096
>>>
>>> As you can see from the number of categories (0), there is no
>>> information in this raster file.
>>>
>>> Can someone perhaps help me figure out why this happens?
>>>
>>> Thanks
>>> Hanlie
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>>> grass-user at lists.osgeo.org
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>>>
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-- 
Micha Silver
Arava Development Co. +972-52-3665918
http://www.surfaces.co.il