Creating thematic maps with hexagons in ArcGIS Online

The process of aggregating and summarizing point data into equal sized connected hexagons is called hexagonal binning. This has become increasingly popular because creating thematic maps with hexagons is an effective way to visualize patterns and clusters in your data especially when a large number points overlapping each other. For more information on hexagonal binning, see our previous blog posts thematic mapping with hexagons and using binning technique.

With the ArcGIS Online July 2015 update, ArcGIS Online spatial analysis tools now added build-in Living Atlas Analysis Layer gallery. The gallery contains a collection of common geography layers such as country, state, and census boundaries useful for many analyses. Also included in these ready-to-use layers are hexbins for different regions in the world with different resolutions.

Here is an example of how to aggregate US tornado locations into hexagons in ArcGIS Online. The following web map shows approximately 19,000 points covering 15 years (From 1994 to 2008) of tornadoes in the USA.

Tornado Locations 1994-2008

As you can see, it’s hard to see where tornadoes mostly occur in the US because points are overlapping each other.

Now let’s aggregate the tornado locations into 25km hexagons. To do so, select Analysis from the menu:

Then choose “Aggregate Points” in Summarize Data category:

The USATornados is the point layer that contains all the tornado locations. To choose layer containing aggregation areas, notice that you have the option to “Choose Living Atlas Analysis Layer”:

From the Living Atlas Analysis Layer gallery, you can then choose “Hexbins” category:

You can see that there are different layers of hexbins available covering different regions and also with different resolutions. We choose “North America Hexbins 25km” for our purposes.

Now make sure you uncheck the option “keep areas with no points” therefore the results will not include hexagons that have no tornadoes in them.

After the analysis is completed, the result layer is shown on the web map. Since all the hexagons are in equal areas, we changed the default symbology to a choropleth map based on the number of tornadoes fall within each hexagon.

Now the pattern of the tornadoes is much easier and to see it’s also more visually appealing.

Here is the same web map zoomed into south Florida area:

With ArcGIS Online analysis tools, it is easier to aggregate points into hexagons because there are ready-to-use hexbins available for multiple regions in multiple scales in the new Living Atlas Analysis Layer gallery. We welcome you to try it out and let us know what you think.

This entry was posted in Analysis & Geoprocessing, ArcGIS Online and tagged , , . Bookmark the permalink.

Leave a Reply

10 Comments

  1. tchapin says:

    How do you get past the feature limit? In the example above does the client need to receive all 19K points to do the aggregating? What if you had 190K points? Seems like a case for server-side clustering/aggregation.

  2. jzlange says:

    I published the US tornado locations as a hosted feature service in my ArcGIS Online organization. Feature services are a more scalable way to publish features, and enable you to go beyond the 1,000 feature limit. The aggregation is indeed ran on the server side by the Esri hosted ArcGIS Online analysis services.

  3. jgenther says:

    @tchapin: There are only limits on the browser’s ability to generate and display graphic symbols for more than 1000 features. Aggregating into polygons, like hexagons, solves that issue too.

  4. cursus says:

    Hi, this may seem like a silly question but I am new to some of these issues. Can all ArcGIS Online accounts access this Analysis tool or do you have to have a paid version? I do not seem to have this button as described. When I do the steps indicated it is still not an option.
    Cheers

    Jeff Chartrand
    Royal School of Military Survey
    UK

    • Nick Furness says:

      Hi Jeff.

      You do need a paid account (sounds like you have a public account), but if you don’t have a login through the Royal School of Military Survey, you can set yourself up with a free developer account which gives you 50 credits a month. Learn more about account types here.

      Note that each analysis tool has a “Show credits” button right by the “Run Analysis” button to tell you how many credits you’re going to use. Worth making use of as you learn about the tools.

      Hope this helps,

      Nick

  5. jwarnke says:

    I like the method of hexagonal binning at different scales. It permits my clients to visualize the spatial data of confidential client data. It also permits the limiting of the number of points displayed in smaller hexagons when zoomed in. I will definitely try it out with a feature service of postal code data (I use postal code points and centroids of dissemination area polygons in Canada).
    I am not familiar with the issues of analysis of hexagon binned data and would welcome any comments on the comparison of the hexagon binning technique to more traditional lattice based aggregation techniques for the modeling of spatial phenomena. Perhaps the analysis of hexagon binned data can be addressed by a server side analytical procedure (service) or is this idea an over simplification of a complex analysis issue?

  6. klassizistisch says:

    I really like this new feature! I just have a question regarding the visualization of the hexagon and why they are drawn a bit distorted? I was trying different extents/larger scales and could exclude the problem of coordinate systems. Is there a plausible explanation for this behavior?

    • jzlange says:

      Great question klassizistisch. The standard for sharing data on the Web is to use Web Mercator projection, which is the projection used in ArcGIS Online. Because this is not based on an equal area projection, the hexagon shapes are drawn a bit distorted. Please keep in mind that the results for analytical purposes are valid regardless of the visual display. A workaround is to create your own custom base map to use in ArcGIS Online that is based on an equal area projection.

  7. szwillinger says:

    Can you use the “Enrich Data” option with the hexbins? If so, is there an option to limit the number of polygons so that you don’t get charged a ridiculous amount of credits?

    • jzlange says:

      Hi Szwillnger,

      Yes, you can use the “Enrich layer” tool with the hexbins. One way to limit the number of hexbins to be enriched is to zoom close and check the “use current may extent” option so that only the hexbins that are in the current map extent will be enriched.