Displaying transparent overlapping polygons in ArcGIS for Desktop?

Question

I'm trying to draw home range maps in ArcGIS 10.1 and am having difficulty displaying them as I would like.

The home ranges are in the form of polygons and many of them overlap. I'm trying to get a display setting that allows all polygons to be displayed at once, particularly where they overlap.

Essentially what I'm trying to do is display the polygons in the same way that the standard primary colour illustration appears, with three overlapping circles of different colours. The important part here is that where the polygons overlap they will combine to make a new colour, thus clearly demonstrating the overlapping area. Another way this is often done is to display each polygon with a unique crosshatching. For instance polygon 1 could have a left-facing diagonal hash, while polygon 2 could have a right-facing diagonal hash. Where they overlap, a cross-hatch pattern would be observed.

Transparency works in relation to other layers in the map, but unfortunately it doesn't seem to work in terms of each polygon within the layer. Same goes for defining the symbology level (essentially they all need to be on the same level).

I've seen this done with many other maps of animal home ranges or other overlapping zones, so I'm assuming there's got to be a way of doing this.

Answer 1

If you are looking for the simple diagonal hatch method you mention, this can be achieved by symbolizing the home range polygons as unique categories. First use the '10% Simple hatch' symbol for all, and then customize the individual symbol patches. For each symbol, click on the Edit Symbol button where you can modify this line fill symbol's color, angle and separation (the offset can also help with multiple overlaps). Unless you have more than five overlaps, using these different settings for each home range should give you a crosshatching visualization that can still be easy to read. (@Llaves link to the blog post is super cool!)

Answer 2

I know this was asked years ago, but putting forward another solution for those looking. You can set individual transparencies within a polygon by adding a new field and assigning transparency percentages. Once the new field is filled in, go to Symbology>Advanced>Transparency and select your field from the drop down. The software will now read your field and set each polygon that level.

Answer 3

Since I only had 7 individual animals I wanted to map, I ended up using the Split tool to separate each individual polygon into its own shape file. Then I was able to set the colour and transparency of each layer separately.