[GRASS-user] Again about direction

[Micha Silver]

Sofina Natalia wrote:

> The problem is I don't have the values "direction" for vector points. 
> The question ist just how can I extract them. I don't know the 
> direction in vector points.
>
Well, points don't really have a direction. Can you be more specific 
about the problem? when you said direction, I assumed you meant "flow 
direction" as in hydrology. If the raster is a flow direction grid, then 
the command below will upload the flow direction from the raster to each 
vector point.

> /
> /
>> /If I understand correctly, you have a vector point layer with an 
>> attribute column "direction". And you have a raster which also shows 
>> directions. What you want is to add to the vector points an 
>> additional column "Raster_direction" which shows directions from the 
>> raster. Is this correct?
>>
>>
>> If so then you have two simple steps. First add the additional column 
>> to the vector:
>>
>> v.db.addcol <vector_layer> col="rast_dir integer"
>>
>> Then get the raster values into the vector with:
>>
>> v.what.rast vect=<vector_layer> rast=<raster_layer> col=rast_dir
>>
>>
>> /
>>> /Many thanks.
>>>
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>> /
>>
>> /
>
>
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-- 
Micha Silver
Arava Development Co. +972-52-3665918
http://surfaces.co.il