[R-sig-Geo] 'Cleaning' unioned polygons using sp and maptools...

[Peter S. Hayes]

Hi List,

Here's a question... I have a watershed polygon that has been 'tiled' 
into separate and non-overlapping cells according to a combination of 
attributes. The original watershed boundary seems not to be available in 
undivided form and I was interested in retrieving it from the divided 
shape file. Using ESRI resulted in several internal boundaries that were 
not removed. Using 'unionSpatialPolygons' produced even more non-removed 
internal boundaries.

Is there a simple means of 'cleaning' this to remove duplicate 
boundaries and no-longer-connected internal boundaries? I have looked a 
little (and admit to being a relative neophyte in using the packages) 
but haven't found anything that appears promising. I can certainly begin 
to appreciate the difficulty of finding and removing these boundaries, 
at least on a conceptual level... a problem in graph theory? (not at all 
my area...)

Thank you all!



Pete