GIS Tool: Hot Spot Analysis

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Point Map of Brewery Locations from the Open Beer Database

Point Map of Brewery Locations from the Open Beer Database

A hot spot analysis, or the resulting heat map, takes a set of points and renders them to show “hot” and “cold” spots based on the points. In the example to the left, brewery points were plotted. By just looking at a map with points, I can potentially pick out areas that I think may have higher concentrations of breweries, but it’s hard to tell for sure. I might think the East Coast around Philadelphia has the highest concentration.

Heat Map of Brewery Locations from the Open Beer Database

Heat Map of Brewery Locations from the Open Beer Database

I then took the same set of data but applied the heat map style in ArcGIS Online to show areas with significantly higher numbers of breweries in white, yellow and red, and a significantly lower number of breweries in darker to lighter blue. I can easily see that St. Louis, Denver and San Francisco all have higher concentrations of breweries than Philadelphia!

In episode 8, we talked about using hot spot analysis to see how fish were using a newly restored habitat site. With a hot spot analysis, you can either get results based on absence or presence, as in the beer example, or weight your points and use the weighted values to determine the significance of presence.  In ArcMap, if you just want to see areas the fish are present, you would use the optimized hot spot analysis tool. This will give you results that look similar to the beer map, and will just show where fish are present in higher and lower concentrations. If you want to not only see where the fish are present, but count the areas they spend more time as having higher significance, you would want to use the hot spot analysis tool.

If you just want a quick map showing hot spots where fish are present but don’t want to mess with these tools, you can upload your data to ArcGIS Online, add it to a map, and symbolize it with the heat map symbology, as I did with the brewery locations.  ArcGIS automagically does the analysis for you. You of course have more control when you use the tools in the desktop software. If you do want to have more controlled results, I suggest checking out the help pages to get more information, because I’m definitely not an expert in hot spot analysis (although the Poop Detective thinks I should be an expert at all things GIS or even remotely related to GIS since I’ve been working with it for almost 23 years). Happy Heat Mapping!