topic Re: Creating a spatial coverage and overlap map in Mapping Questions

Creating a spatial coverage and overlap map

BenSimpson — Tue, 02 Jun 2015 12:08:12 GMT

Hi all,

I would very much appreciate some help in working out how to create a particular type of layer/map.

I have a polygon layer which represents spatial coverage of three different categories. At the moment these categories are represented as separate polygons. In certain areas the different categories overlap each other, so I want to create a map which represents areas where there are more than one category. This would mean that the final map should show seven different spatial classifications, as shown below:

Category A

Category B

Category C

Category A and B

Category A and C

Category B and C

Category A, B and C

I am stuck on working out how to create this sort of map/layer. If anyone could point me in the right direction so I at least know where to begin then that would be great. Sorry if I have not explained it very well, please ask if you need anymore information.

Thanks,

Ben.

Re: Creating a spatial coverage and overlap map

JayantaPoddar — Tue, 02 Jun 2015 12:36:43 GMT

Hi Ben,

Add a text field to each of the three layers, with values "A", "B" and "C" respectively (use Field Calculator).

Do a Union of all the three layers.

Dissolve the union layer with the above three fields. The resulting layer will have 7 features with the above combination. Add a text field to the dissolve layer and define the desired values like "A", "B", "C", "A+B", "A+C", "B+C", "A+B+C".

Now if you want independent individual polygons in the feature class, you could use multipart to singlepart tool.

Re: Creating a spatial coverage and overlap map

BenSimpson — Tue, 02 Jun 2015 13:29:31 GMT

Thank you, that has worked perfectly much appreciated.