Why would Update (Analysis) tool from ArcGIS Desktop 10.0 create duplicate features in file geodatabase?

Question

I am attempting to use the Update (Analysis) tool to update a right of way (ROW) polygon feature class with a roads polygon feature class. The ROW feature class completely contains the roads feature class and I want to 'etch' the roads into it so I have one feature class with different attributes in one field for the roads area vs. non-road area.

The feature classes have identical fields; for my field of interest, I've given different values to the features in the roads vs. ROW classes.

On my computer, this works as expected - the roads are 'etched' into the ROW with the appropriate attributes so I can distinguish roads from non-roads.

However, on my colleague's computer, the update does not 'etch' the roads in...instead, where the roads are, the update creates two polygons with identical geometry - one with the road attribute and one with the non-road attribute.

I haven't been able to find anyone else with this problem by googling. Has anyone else encountered this? Any idea of potential causes?

Thanks!

Answer 1

I found a two-part explanation and solution to this problem.

First, my colleague had apparently reversed the input/clip feature classes for a clip earlier in the overall process. Fixing the clip inputs resulted in the update tool working as expected.

Second, it appears that the root cause of the update issue was that the clip input problem created invalid geometry (specifically self intersections). Even with the clip inputs reversed, if we run a repair geometry to fix the self intersections and THEN run the update, the update tool works as expected.