Overlay Toolset–Full Functionality using and ArcView License
Within ArcInfo the Overlay toolset contains a rich set of tools i.e. Erase, Identity, Intersect, Spatial Join, Symmetrical Difference, Union, and Update. But if you only have an ArcView license (aka the majority of GISers out there) then you only get Intersect (two inputs only), Union (two inputs only), and Spatial Join.
So what do you do if you only have ArcView? Well thankfully it isn’t very difficult to use the already existing capabilities of ArcGIS and a little bit of Python programming to roll your own.
Intersect and Union are the easiest ones to overcome, all you need to do is know how to split a multi-value list and loop over the results (yeah you might not be able to use the ranks option…but how many people actually use that and don’t have AI already).
Then all you need to do is get back to basics. For example, a symmetric difference is essentially a UNION minus an INTERSECT. Erase is a little trickier but still doable via some additional select by’s and some light post processing.
Identity, well the tricky part here is the “keep relationships” option. Personally I never use that option because of the way the attributes get renamed. So with this one simplifying step an identity can be created chaining the existing tools and again some minor post processing.
Update is an interesting one but still relatively straightforward – often wondered why this one existed in the first place since it is remarkably similar (but not exactly the same) as an erase and append.
Anyways, in the span of a morning we were able to write the full suite of Overlay tools so that even at an ArcView license level you can get a reasonable hand drawn facsimile of the functionality available with ArcInfo.
if you too would like these and other tools available and would like to learn how to make these tools yourself then sign up for the Advanced version of our Geoprocessing with Python course via BrainCandiii.
