Ask A Cartographer

Generalization and OS Mastermap

January 27 2010 | 0 comments
Categories: ArcGIS Methods, Map Data

I am trying to do some generalization with OS Mastermap data and ending up some questionable results. I have created a new layer and copied some selected buildings to it from the Topo_Area layer.

Where building polygons are adjacent, I have managed to get perfect results from the 'Dissolve' tool.

However, when I try to use 'Aggregate' or 'Simplify Building' tools, the results do not come out as expected. Attached is a pdf showing before and after simplification, with arrows pointing to the parts that should have been removed (other sections seem to have worked ok).

Does anyone have any suggestions?

Many thanks.

Mapping Center Answer:

It appears that the simplification tolerance you specified was probably too small to eliminate the parts indicated by the arrows. Gradually increase the tolerance value and the you will likely achieve the desired results.

This is the same for many GP tools -- if you don't like the results the first time, make some changes and try again. This is especially true for generalization, where the results are incredibly subjective on a user by user basis.

If this doesn't solve your probelm, please get back in touch!

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