Erase within a feature class - Planar enforcement

Question

I´m using ArcGIS v10 ArcInfo.

I´m working with a feature class that has 5 features which are waterdepths (1 to 5m). These features are overlapping each other. What I need, is that they are not overlapping. To achieve this I used two differend methods that are leading to the same goal:

1. I extracted each feature in a single feature class (1, 2, 3, 4, 5). 1 is the biggest overlapping 2, 3, 4 and 5. So I erased 1 with 2, 2 with 3, 4 with 5, merged them and had the feature class I needed.

2. I ran the union-tool (geoprocessing) on the feature class itself. The problem is, that all overlapping parts are created additionally as new features. Instead of the 5 features I need, I get 10 features more which I have to sort and erase by hand.

My question: Is there a tool or method that does this without so many steps by hand? I´m able working with QGIS and ArcGIS v10 ArcINFO.

Answer 1

Without your Question including a graphic it is hard to be certain but I think you are saying that each feature at one depth is wholly contained within a feature at the shallower depth.

Consequently, I think your method 1 is the sensible way to do this because that procedure could be turned into a model or Python script without too much effort.

What you are achieving in this process is known as planar enforcement.

Answer 2

It depends on how your features overlap, but you could give a quick try to this method :

1) Convert from polygons to lines

2) Convert from lines to polygons

You will lose the attributes of your polygons, but you can recover them using polygon centroids. I guess that your features are some kind of contour lines, so the number of points in a spatial join "one to many" should be proportional to the depth. You can also adapt this method to recover your attributes automatically in a safer way.

Note : for visualization only, you can manage this easily using symbol levels