[GRASSLIST:640] overlapping polygons from bad shapefile

[Dylan Beaudette]

Greetings,

Received a geology map of our survey area in shapefile format, but some of the 
polygons are overlapping. Upon import into grass with v.in.ogr, the 
overalpping polygons are split according to the rules of topology at nodes (i 
think). 

Here is a link to the results of a quick `d.vect -c`

http://169.237.35.250/~dylan/temp/overlap.png

The red arrow points to an area where an underlying formation overlaps with 
overlying Quaternary sediments -- rather common in reality, but difficult to 
capture without overlapping polygons...

I am interested in classifying this map, and rasterizing the result. However, 
v.to.rast does not quite produce the output that I would like in areas where 
polygons are overlapping. i.e. v.to.rast is using the attribute from the 
"lower" polygon where the two geologic unit polys are overlapping. Is there 
anyway, short of manually removing these trouble polygons, to make v.to.rast 
use the attributes associated with the "uppermost" overlapping polygon?

Any ideas would be appreciated!

Cheers,

-- 
Dylan Beaudette
Soils and Biogeochemistry Graduate Group
University of California at Davis
530.754.7341