[GRASS-user] buffer vector within a given area

[Moritz Lennert]

On 22/04/09 20:39, Martin Schweizer wrote:
> Hi
> 
> I have a question which is a bit complex. Hope i can describe it ;-).
> 
> I have a point-vector layer (the citis) and a raster layer with 1 and
> ZERO cells (The potenial agricultural land). One categorie in the vector
> layer is the land (Squaremeter) that hast to be cultivated for each
> point (city). The question is now: How can I calculate and display,
> which cells of the raster map (potential agricultural land) hast to be
> cultivated? Must be some sort of buffer or neighbourhood.....?

Assuming that this agricultural land is the same in all directions of 
the city, create a column which contains the radius of the circle that 
encompasses the land needed (i.e. if my memories of geometry are 
correct: sqrt(surface/pi) and feed the name of this column to the 
bufcol= parameter of v.buffer (or feed the formula directly to the 
bufcol parameter, but this only works if you use a db-backend which has 
a sqrt function, i.e. PostgreSQL).

Moritz