[GRASS-user] If not v.overlay, what?

[Micha Silver]

On Wed, 2011-07-27 at 14:42 -0700, Rich Shepard wrote:

> I have a map of drainage basins and another of the project property
> boundary. Of the 4200+ basins in the map, the property is in only a dozen or
> so. I'm trying to overlay these maps to produce a union that has only those
> basins that drain the property. v.overlay with operator=or yields a combined


Use "AND" not "OR". 
OR=Union, that is combining all features of both vectors
AND=Intersection, that is, just areas or lines covered by both vectors


> map of _all_ basins and the property[1] so either I'm not correctly applying
> the module, or the resulting map needs more processing with a different
> module. Please point me in the right direction to get the results I want.
> 
>    After I have a map containing only those basins overlaid by the property
> boundary I want to use v.overlay to clip the stream networks in these same
> basins. I assume that v.overlay with op=and will do this nicely. My question
> is then what process will allow me to extract each drainage basin with its
> stream network and portion of the property for terrain and hydrological
> analyses and modeling.
> 
>    I have another issue with the DEM, but that will be on a separate thread.
> 
> Rich
> 
> [1] Using the wxPython GUI with v.overlay I did not see a data entry widget
> to select the operator. It apparently defaults to 'or' but if there's a
> radiobox to select 'or,' 'and,' 'not,' or 'xor' I did not see it.
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