Is there any coefficient that can indicate T-shaped polygons ?
Examples of T-shaped polygons :
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I don't know of any off-the-shelf solution. However, here's an idea which you could work up into a script or possibly in Model Builder (WARNING- I don't have ArcGIS to hand, so can't test it, and some experimentation will be needed):
- The work-flow I have described there will (if it works) also pick up X, Z and L shapes. However, if you make you algorithm for comparing segment orientations rather more sophisticated, then you should be able to refine it to detect T shapes by checking the connectivity of the various segments.
- I also can't remember off-hand whether the collapsed lines are presented as multilines or single lines for a given left-right casing FID combination or how the process handles the branching. Is there an angle at which a branch is presented as a separate line for instance? These factors will determine what you do next.
- I anticipate that you will need to possibly do some reorganization of the lines so that they can be handled sensibly by your algorithm the determines the T shape by orientation of the lines. Therefore, you will need to experiment a bit here.
- And another thing... once you have determined the branching pattern of your skeleton and decided that it is essentially T shaped, you will need to compare that to the polygon's area to perimeter ratio. A 'fat' polygon that you don't want to count as a T may result in a T shaped skeleton but will have a smaller perimeter to area ratio. Some of these issues can be resolved by setting the minimum_width option of the
Collapse Dual Lines tool but a sanity check seems prudent.
Please remember, this is just an idea and you'd need to develop the solution yourself, but it is an approach I might start with.
If you don't have a suitable licence for these tools in ArcGIS then you could use/buy FME. I don't think ET GeoTools/GeoWizards will help with creating the straight skeleton but they might help with the how you present your lines to the final algorithm to determine T shapes.