[Openspace] Dissolved Shapes May be Corrupted - check your weights properties

[alfred nucci]

I encountered a similar problem with creating a contiguity file from 
arcview shape file created with dissolution tool (in arcview 
geoprocessing); this also occurred when I  imported this shape file into 
arcgis and when I recreated the shape file source data.  I was able to 
clean the shape file by creating a personal geodatabase -- this is the 
default file format for arcgis, i believe -- and invoke the topology 
cleaning and verification tools in arcatalog.  By clean I mean remove 
the islands -- presumably corresponding to polygon slivers resulting 
from dissolution operations -- and obtain a shape file (upon export from 
arcgis) with few islands.  My example is us counties (including Hawaii) 
with boundaries standardized to account for changes between 1900 and 
2000, including independent cities (e.g. VA).  I went from a shape file 
of 3065 counties and over 60 islands -- most corresponding to county 
boundary standardization operations -- to one with eight,four being the 
Hawaiian islands.

Al Nucci

David Long wrote:

> I've encountered problems with contiguity matixes created from 
> shapefiles generated by a dissolve function in ArcGIS 9.  When looking 
> at the properties of a queen contiguity matrix I'm seeing islands 
> where I should not.  There seem to be "ghosts" of the dissolved polys 
> lurking in the file structure somehow, such that those polygons that 
> were dissolved register in GeoDa as islands.
>
> The good news is that one can easily circumvent this problem using the 
> dissolve function within the Geoprocessing Wizard Extension to ArcView 
> 3.3!
>
> Dave
>