FME Spatial Join One to Many

Question

I am relatively new to FME and have been attempting to carry out my usual ArcMap tasks in FME instead.

One tool that I use frequently in ArcMap is Spatial Join, specifically with the One to Many join operation.

I thought that I had successfully recreated this in FME using the SpatialFilter transformer, with the following settings:

However, I realised after using it, that if I have multiple filters intersecting multiple candidates, it is only returning the candidate for one of them. For example, if "A road intersects with A zone", and "B road intersects with A zone", the transformer only returns "A road in A zone", while "B road" has no merged attribute data.

I then tried using the AreaOnAreaOverlayer transformer, but this gives information for every feature and takes about 30 minutes to run, in comparison to the Spatial Filter which took about 2 minutes. I think I must not have the AreaOnAreaOverlayer set up correctly.

My question is which transformer I should be using in FME to recreate the SpatialJoin tool in Arcmap, specifically with the one to many join operation.

Answer 1

So the SpatialFilter isn't quite right here. Yes, it merges information, but only 1 piece, because it's only trying to determine whether a feature overlaps. It's a yes/no result really. For example, I have parks and cycle paths and want to identify which paths pass through a park:

This works fine. I know that 19 of 39 paths pass through a park. FME only tells me the first park it matches because at that point the test is done (yes, it's a match).

There is a better chart for deciding on the right transformer, and it's this one:

...from this page on the knowledgebase.

I wouldn't use an overlayer transformer because they're designed to actually cut the data where it overlaps. In this scenario I would use the SpatialRelator. It works like the SpatialFilter, but it continues and tests for a match against all features.

The key transformer parameter is the Generate List option. With this I get a list (a specific FME data type) that records all the parks that a cycle path passes through:

It even tells me the type of relationship if important.

So what you can do with that list is put it into a comma-separated value (ListConcatenator) or create a separate record for each list element (ListExploder) or do all sorts of other things (use a List* transformer or AttributeManager - for example).