Feature to Point does NOT center point

[Anonymous User]

I have a process whereby I create points from 2 different polygon feature classes and then compare whether the polygons have moved or changed shape based on XY coordinates of the point feature classes.  To do this I use the Feature to Point tool (Data Management/Features) and set it to place the point inside the polygon.
In ArcGIS 9.3.1 the points would be placed in the center of the polygon.  In ArcGIS 10 (sp4) the points seems to be placed almost anywhere in the polygon.  Therefore if I add XY coordinates and compare the two new point feature classes the comparison finds points with differentiating XY coordinates but the polygons haven't changed.

Is there a way to get the feature to point tool to place the point in the center of a polygon?  Or is there another tool?   Any ideas are welcome.
thanks in advance

.... and for the heck of it I just tried NOT checking "inside" and voila, the points are in the middle of the polygon.  Rather bassackwards and not-intuitive....

[DanLee]

Which sets of points, the blue dots or the purple hexagons, did you create using 10 SP4? And the other set of points were produced by 9.3.1?

As the image shows what's expected, the Inside points are not necessarily at centers.  May I ask what made you to choose the Inside option instead of the centroid option (uncheck Inside)? For comparing shape changes, if the parcels have unique IDs or attributes and the changed parcels carry the same original IDs, then centroid points would be more reliable, even if they fall outside of polygons; you just need to make sure you compare the centroids with the matching attributes. Could that work?

[Anonymous User]

Both the blue dots AND the purple hexagons were made in ArcGIS 10 with the inside checked.  When I did the same process before upgrading to ArcGIS 10 the dots would be placed in the center.  That's why I chose Inside, b/c in 9.3.1 it placed the points in the center.
I would like to use the Feature Compare tool but one set of data comes from an outside source and does not maintain a unique ID so I can't use that tool.  We create our own by combining a portion of 2 attributes and the XY coordinates, hence why I make the points and why it's ideal for them to be in the center.

[DanLee]

It is still not clear to me how both the blue dots AND the purple hexagons were made in ArcGIS 10 with the inside checked. What made them different? Are they from the same set of polygons (I can only see one set of polygons in the map)?

The Inside option doesn't produce centroid by design; it finds a "good-enough" location inside a polygon. This location may happen to be at the center or near the center, or just appear at the center, but not always at the center. This is true in 9.3.1 as well. Therefore, using the Inside option is not really reliable unless the matching features from both datasets have a common attribute.

If the shape of parcels are very similar in the two feature classes, perhaps you can try the Centroid option (uncheck Inside). Of course you would need to check for cases where a parcel has a concave "C" shape and the centroid location falls outside the polygon or in the wrong polygon.

Since you mentioned that your data are from different sources (internal and outside), is your goal to align them or to update one using the other? If so, you might have a use case for our on-going conflation project. Could you share a sample area of the two datasets, not too large to attach on the forum? Or if you like, you can send to me by email: dlee@esri.com. I'd appreciate it.

[DanLee]

I just want the readers to know that Hilary and I have taken this offline since yesterday. I investigated the issue on Inside point location using her parcel data; apparently our enhancement on the Inside option made after 9.3.1 has avoided some odd point locations, but affected some good locations. Her case is reproducible with a subset; we will try to look into further enhancement on this.  Thanks, Hilary, for bringing this up and sharing the data with me.  You may submit an enhancement request with Esri Support as well.

[Anonymous User]

This problem has been registered as a bug
NIM084360 - [Feature to Point Geoprocessing tool gives inconsistent results when running tool in v9.3.1 vs. v10]

thanks all for your assistance 😄