Hello everybody !
I would like to compare values for raster and vector points at positions of vector points. Raster is filtered with edge detection function. And as compared value should be “direction”.
How can I get now the information about direction in each point for vector map? Vector points should have one’s own values of the direction. Then I’ll compare this values from raster and vector.
Many thanks.
Sofina Natalia wrote:
Hello everybody !
I would like to compare values for raster and vector points at positions of vector points. Raster is filtered with edge detection function. And as compared value should be "direction".How can I get now the information about direction in each point for vector map? Vector points should have one's own values of the direction. Then I'll compare this values from raster and vector.
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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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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Micha Silver
Arava Development Co. +972-52-3665918
http://surfaces.co.il