Modern GIS: Spatial Analysis

BrianBaldwin

This is the 3rd blog in a 6-part series highlighting the core concepts of a Modern GIS. To view the other blog posts – please visit this page Modern GIS Core Concepts

Over the past few years, Esri’s Education team have been discussing the technology shift and the need for GIS coursework to move from desktop-centric patterns to those that include the web. Desktop GIS is still an integral part of the story – but it is no longer the focus of the story. Desktop GIS is vital for data management, advanced analysis, and cartographic production – but many of those workflows are now part of a web-based context. Desktop tools can now seamlessly consume web-based services published by authoritative geospatial agencies and individuals across the globe. Desktop GIS can publish map services and layers to the cloud – to be consumed by web-based applications and tools, and desktop GIS can edit and manage web-based data and layers.

Through this series, we are asking: So, what does a course look like that focuses on the fundamentals of GIS but adjusts to a more web-centric paradigm?

In this blog, we will be looking at spatial analysis.

Pentax Digital SLR 4 Life!

The first generation of the iPhone included a 2 MP camera. At the time, I scoffed at the fact that a ‘phone’ could replace a fully featured Digital SLR. With my trusty Pentax in tow... I could capture low-light shots, adjust the film speed for ‘action’, and set a wide aperture to capture nice ‘blurred background’ portraits. Well, as long as I had the right lens, remembered what an f-stop is, and didn’t forget any manual settings. Sorry to break it to you 1st Gen iPhone… but you’re not a ‘real’ camera.

More than 17 years later and my Pentax is collecting dust in the corner.

When it comes to GIS, the same can be said about spatial analysis. Around 10 years ago, desktop GIS was the ONLY option. If students were going to be exposed to the basics of why spatial is special – they had to dive headfirst into ArcMap, hundreds of toolboxes, and SQL. It was a lot, but it was the only

The real ‘aha’ moment of GIS for many new learners is often related to spatial analysis. What is the best location to build the park? Where are food deserts located and why? Why is wildfire more prevalent there? Understanding a spatial pattern in a new way is the ‘magic sauce’ of GIS, and for years – these inquiries were only possible in desktop GIS, which many times, were only earned through a lot of pain.

With the rapidly advancing capabilities of web-based GIS, spatial analysis is now possible via python notebooks, the ArcGIS Online Map Viewer, API’s, as well as desktop GIS. There are simply more options available to users, the technology has advanced to the point that spatial analysis conducted on the web is a viable option for many.

I can remember all too well – staring at SQL syntax in the ArcMap field calculator with an error that I had no understanding of. All I wanted… was to see what houses might be impacted by floodwaters. “Please computer, please just let me update some attributes, run a buffer, and make a selection.” Just like the next GIS professional, I love trading war stories over Avenue, VB Script, or 8 hour edit sessions that I forgot to save… but was an intro GIS course the right place to start earning those stripes?

Buffers, Joins, and Overlays

Just as it does for mapping and cartography, it comes back to the fundamentals. Forgetting about the software and tools for a minute… what do we want learners to actually take away from the limited time we have to spend on spatial analysis in an introductory course? What are the course objectives? Do we want to inflict scars and pain? Or inspire them to enroll in follow-up courses that allow them to dig deeper?

At its most basic, we want students to understand that ‘spatial is special’. That asking a spatial question involves a different type of inquiry than that found in statistics or data science. The UCGIS Body of Knowledge provides a fantastic set of topics – especially when we look at the ‘Building Blocks’. (Analytics and Modelling Body of Knowledge: https://gistbok-topics.ucgis.org/AM-02)

Areal Interpolation
Classification & Clustering
Boundaries and Zone Membership
Buffers
Overlay
Grid Operations and Map Algebra

Looking through the full list of ‘Building Blocks’ from the UCGIS Body of Knowledge these are (not surprisingly) many of the core topics that we want students to not only understand, but to apply, and evaluate in a meaningful way.

So – are there any of these ‘building blocks’ that can not be accomplished in web-based GIS? To put it simply… no. With recent additions to the ArcGIS Online Map Viewer, it’s now possible to run any of these fundamental spatial analysis operations. While ArcGIS Online can be a fantastic location for introducing these concepts and running a great deal of real analysis, there is obviously an important place for desktop GIS. One of the fun aspects of the classroom is letting learners find that line, poke it, and discover when and where an analytical approach makes more sense in a different tool.

Beyond just the ‘building blocks’ – there are also hosted tools that cover network and location analysis, spatial statistics, spatial autocorrelation (local and global), cluster analysis, kernal density, and more.

Making It Real for Students

As a student – we want to understand how this course relates to us. Learners want course content to be meaningful, impactful, and relevant. Teaching analysis methods and approaches and then letting students dive right into applying them is frictionless in ArcGIS Online.

One of the most important aspects of ArcGIS Online is the ability to quickly search for and use data. Thousands of layers are available from non-profits, government agencies, corporations, researchers, my crazy Uncle Larry (look at the data sources!), and more. The best sources of information also contain detailed metadata which anyone can read through.

Rather than spending time trying to find data, students can spend their time asking questions and analyzing information.

In this example, the following dataset includes state, county, and tract level attributes for Race and Hispanic origin from the US Census Bureau’s American Community Survey (ACS). Looking at this dataset – there are spatial clusters related to race – but what do they really mean? Do the clusters of Hispanic or Latino populations (shown in green) represent a statistically significant cluster? What does it mean at different spatial resolutions? Not only can students find this authoritative data quickly, but they can also start to use analytical tools within ArcGIS Online to ask those questions.

The default symbology that is presented to learners is just a starting place. Students can use different attributes, colors, symbology schemes, class breaks, etc. Leaners can also use select and filter tools to work with the data they are interested in. In our example, this ACS dataset contains over 67 attributes that can be used for visualization and analysis.

In the ACS dataset, there is a field for ‘Hispanic or Latino Population’, but what does that mean? With the metadata just a click away, it’s easy to encourage students to explore what values the field contains by sending them to the layer properties (which defines this as an ‘integer’ field showing the total population).

In the analysis tools pane, students can then search and find the tools that they want to run. In this case, we selected the ‘Find Hot Spots’ tool, which is using the Getis-Org Gi* statistic. What distance band settings should I use? Should I normalize my data or divide it by another attribute? What do these settings mean and how do they influence my results?

The output of the tool is a new layer, with a Z score, P value, and the total count of neighbors that were evaluated. This layer comes with a pre-defined symbology… which can be easily overridden. The analysis tools now include a 'history', to let learners look at prior model runs, adjust parameters, and then create a new output. In about 5 minutes, a learner could generate 3 results with varying parameters, and create a simple swipe app to compare them.

With the hosted analysis tools, students can discover data that they care about, ask questions related to that data, and test their hypotheses. The hot spots tool is just one of the dozens of other tools available in ArcGIS Online. ArcGIS Online has a lot of analytical capability, but it does not come close to the array of tools and analysis that are available in ArcGIS Pro (the incredible Suitability Modeler, GeoAI tools, spatial statistics, 3D analysis, field calculator, and hundreds of others). When it comes to large datasets, complex analyses, imagery workflows, chained model processes, and other specialized needs… desktop GIS is the required tool. Yet, the world of web-based analysis has come a very long way and offers a great deal that students and faculty can utilize.

In Summary

To be honest, a few weeks ago I dusted off my Pentax, changed the lens, and loaded in some fresh batteries. In a few weeks, a total solar eclipse was going to take place and I was going to attempt to get some photos of it. I would only have a few minutes to try and capture the moment and I needed some fine-grained control as this was a fairly specialized use case. After the 5-hour drive to Vermont… it was over in 3 minutes – and I had a handful of photos that weren’t too bad to show for it. The camera definitely did a better job than my phone. But, as I folded up the tripod, took off the 300mm lens, and put my camera in its case, I took out my phone… because it can do everything else.

Resources

The following is a small subset of resources that you can use as lessons, labs, or supplemental material for a course. Please explore any of these locations further, as there are hundreds of fantastic resources available for spatial analysis in ArcGIS Online.

Modern GIS: Spatial Analysis

Pentax Digital SLR 4 Life!

Buffers, Joins, and Overlays

Making It Real for Students

In Summary

Resources

Esri Academy

Learn

Book/Texts

Documentation/Tutorials

Other