The slivers are in your base data I suspect, and any program that does what
you ask will do the same. I wrote the original mbx for ERSIS, and have a
fair idea of how it is working. The slivers are created because of two
adjoining polygons do not have the same nodes along their common side. The
program is simply selecting adjacent objects with the same code and using
the combine region function in mapinfo to create new regions. You could
try simply combining the regions using MapInfo and seeing if it gives a
different result, but I doubt it.
I would suggest that you actually need to clean your data up. The one
justifyable use of ArcInfo is its clean-up and polygonising capability (a
quote from a local ArcInfo stalwart who now uses ArcView for most
everything else), but there are other products around that could do it for
you. Maybe TopoLogic at www.vecvision.com ?
One that I have used to do this is a program I wrote that buffers each
object first, then cuts it back by the surrounding objects. This may get
rid of your slivers, but it is very much a hack and not something that
could be supported. Also the eternal error in overlaying polygons makes
this program flakey. If left unattended, it will expand the extents of any
polgons that do not have adjacent polygons by the buffer distance as well.
See how you go and let me know of your success or if your still in
trouble.
Robert.
-----Original Message-----
From: Reid Melanie [SMTP:[EMAIL PROTECTED]]
Sent: 01 June 1999 09:28
To: '[EMAIL PROTECTED]'
Subject: MI Overlay Tools
Hello
Does anyone know of a .mbx similar to the Combine Adjacent.mbx from the
ERSIS GIS Toolbox that appears in the Overlay Tools ?
This .mbx creates a new table as a result of a merge of adjacent objects
with a common attribute in a specified field (combining adjacent regions
based on a common field). I have used this .mbx on a large dataset and
found that it creates slivers where some of the polygons join. Therefore
rigourous checking has to be done .
Thanks
Melanie
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