Q: vector map patching

[Ben Horner-Johnson]

> From: neteler at geog.uni-hannover.de (Markus Neteler)
> Subject: Q: vector map patching

> currently I have the problem to merge a small vector map
> in good digitizing quality and a second in less quality. 
> The small one is part of the second - I want to *replace* 
> a part of the map with less quality by overlaying this 
> small map:
> 
> ------------- 
> |less qual. |
> |           |
> |           |
> |  |----|   |
> |  |good|   |
> |  |qual|   |
> -------------
> 
> How to perform such replacement in GRASS? I feel that v.patch
> will just overlay both maps.

Would it work to use one of the math functions on the region you want to
replace?  In other words, multiply all nodes within the good-quality area
by 0 and then add in the replacement nodes, then output the final full-grid
as a separate entity and work with that?  I know this works in other situations,
but don't know enough of GRASS to give you the exact commands.  Is there an
easier way?

Ben Horner-Johnson
ben at earth.nwu.edu