I have a spatial data set that shows areas of use (several different types of use) on the landscape. I am looking for ways to overlay these spatial use layers so that I can show where the areas of highest use (hotspot locations) as well as areas of moderate use and areas of lowest use. How can this be best achieved?

  • When you say you are looking for "highest use", are you asking for regions that have the highest number of different uses? If so, you could add a "Uses" field to each layer and initialize it to 1. Then do a spatial join of the layers, setting the field-mapping parameter to add. When you're done, each region in the result will have a Uses value equal to the number of layers that overlapped the region. (Of course, you really have to do a sequence of spatial joins of layers, first two layers, then each additional layer with the result of the previous join.) – Llaves Jun 2 '13 at 19:30

I have done something similar for possible habitats analysis.

  1. For each shapefile in the analysis (criteria types for habitats), I created a field (integer) called weighting and assigned it the value 1.
  2. Then I used the union tool to union all the layers.
  3. In the newly created union shapefile, I created a tally field and tallied up all the weighting fields to get a total weighting for that row.
  4. Based on the tally, the higher the number the more criteria for possible habitat, occupied the same area.

At the time, this was the only method I could think of but after reading Llaves comments, that's another method I will now try. Hope this is some use.

  • Thank you for the input. Llaves, I am pretty new to GIS so excuse my ignorance, but does this mean that I should create another field and for each use polygon and give this field a value of one for each polygon? Also, I assume that the 'field-mapping parameter' options will come when I begin using the spatial join tool? After the spatial join is completed, with only 2 layers at a time, will I then have areas of overlapping use (new polygons), that have a use value associated with them? Is this correct? – user19497 Jun 26 '13 at 17:04
  • user19497/user18747 Please merge your two accounts so that you can comment in this thread. – whuber Jun 26 '13 at 17:50

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