Parcel Overlay

  • 18 April 2018
  • 2 replies

Hello all. I am relatively new to FME. I’ve completed the basic and advanced FME tutorials, but that is where my experience ends. I’ve been struggling with a particular problem for some time now. I’m not sure if FME is the solution or not, but I really enjoy working with FME, so I’m hoping it is. I am a GIS Analyst and I am hoping to not have to fall back on geoprocessing to complete the task. I work for a County Assessor’s office and I’m trying to solve a problem.

Our parcel numbers consist of a book number(!), page number and item number (e.g. 999-99-999, respectively). We have polygon boundaries that represent book numbers that were created by a mixture of parcel book numbers, PLSS boundaries and roads. They were created a long time ago and are not to be changed, as much as possible.

Parcels are changing continuously throughout the year. For simplicities sake, I have parcels with book numbers A and B. I also have book boundary numbers A and B. When I overlay parcels with book number A onto book boundary A, I need to determine which parcels fall within book boundary A and which parcels with book number A fall into book boundary B, or simply just are outside of book boundary A. The parcels with book number A that fall within book boundary B are what I need to find so that I can update the book boundaries. We have over one million parcels and a thousand book boundaries, so it has to be solved programmatically.

I have searched the FME knowledge center and tried every transformer that can I think to use. This is my last resort. Thank you for any and all help.

2 replies

Userlevel 4
Badge +13

Hi @cpollard2018 Have you tried the SpatialRelator? Direct a copy of every polygon into both the Requestor and Supplier ports and test where "Requestor Overlaps Supplier".

Hi @cpollard2018 Have you tried the SpatialRelator? Direct a copy of every polygon into both the Requestor and Supplier ports and test where "Requestor Overlaps Supplier".

Thank you Dan for the reply. I tried the Spatial Relator. The only test items that are available are Requestor contains, is within, equals, intersects, or touches supplier. I'm assuming that you mean "contains" or "is within". Just want to be clear on that to be sure that I am not missing a concept.



It did seem to work in a way that I wasn't expecting. I used parcels as the Requestor and the large boundaries as the Supplier (the parcel is asking the big boundary if he is within the big boundary or not right?). The only way it seem to work is to test whether the Requestor contained the Supplier, not the other way around, as I was expecting. A little odd to me, but it seemed to work.



Now I want to take it a step further. As the parcel is being overlain onto the larger boundary, I need to be able to test whether the value of parcel is equal to the value of the large boundary it overlays. In 90 percent of the cases, it should. I'm trying to find those that don't. As an example, a parcel's name is 500. The Spatial Relator figures out the big boundary that it is laying on top of (all parcels are going to be on top of some big boundary, in every case). In most cases, the big boundary is going to have the same name of 500. But in some cases, the big boundary name will be something like 400. So I'll have a mismatch in name. I need to find those parcels. And when I speak of "value", I'm referring to the underlying data associated with the features, which is in a geodatabase feature class.



Again, I hope I am not confusing and thank you for your help. What you suggested may very well be what I was looking for.