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I am not a GIS person, but I need to understand an aspect of the project I'm working on.

We are taking an ArcSDE layer, and importing it into FME. I now need to do some checking of the data. In ArcSDE I did topological checks to find if the layers were "vertically coherent". How would I do this in FME?

  • Vertical coherence: to me vertical coherence is that the boundaries of one polygon is within a certain tolerance level of another in a different layer that "overlaps". The boundary lines are the same.
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2 Answers

I think there is more than one way to do this in FME Workbench

I would investigate:

ArcSDEQuerier http://www.fmepedia.com/index.php/ArcSDEQuerier

GeometryValidator http://www.fmepedia.com/index.php/GeometryValidator

Nearest Neighbour http://evangelism.safe.com/fmeevangelism18/ (Credit to Mark Ireland)

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Let asume you have two polygons "a" and "b" and you want to make sure they have the same geometry or if not what the is the distance of shift between them: You can try to investigate it using set of trasnformers to make the analyze available at "vertex level": 1. attribute creator - to name each polygon A and B, 2. Chooper - to make your polygons, polylines single vertices ( each vertex will inherit its name/ other attributes from its parent polygon) - set the maximum vertices to 1. 3. Matcher - set "Match geometry" to 2D and stream vertices to given ports: Matched, single matched, not matched. If the polygons have the same geometry any verites shouldn't be send to "not matched" Port.

To calculate the distance of shift you can make some extra steeps after using Matcher. Using output from "Not Matched" use: 4. Tester - to separate vertices coming from A from those coming from B. 5. NeigborFinder - to find the closest candidate. 6. Reprojector - to change the projection to metric one 7. PoinConnector - to make the line between connected pair of vertices 8. length calculator - to calculate the distance of lines.

Sorting by lenght will probablly give you an answer what is the value of the biggest shift between those two polygons and the same time what value should be set in tolerance field (in any GIS) to make topology normalization work. It's probably not the easiest way to achive what you're looking for but give good insight how flexible FME can be.

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