ArcGIS Pro Essentials: How to Understand Spatial Errors in Map Datums and Projections

By Nicolas R. Malloy December 3, 2024

Every GIS project has an accuracy question hiding in the background: Can I trust what I’m seeing on the map? In this lab, you will use ArcGIS Pro to explore two of the biggest sources of spatial error, map datums and map projections. You will learn how datums define location on Earth, how projections transform the globe into a flat map, and how both choices can affect distance, area, shape, and layer alignment. The goal is not to memorize definitions. The goal is to build the habit of checking spatial references and catching problems early, before they quietly compromise your analysis.

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Estimated time to complete this tutorial: 4 hours

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Learning Outcomes

Readers should be able to accomplish the following outcomes by the end of this tutorial:

• Summarize the steps for creating and organizing a project workspace folder structure.
• Illustrate the ability to download data from a public source.
• Create a file geodatabase.
• Practice converting shapefiles to a geodatabase feature class.
• Add XY data in ArcGIS Pro.
• Exemplify the use of proximity operations such as buffers.
• Analyze distortion patterns using Tissot’s Indicatrices.
• Troubleshoot the causes of spatial errors.
• Solve data alignment problems in ArcGIS Pro.
• Insert essential map elements using ArcGIS Pro Export a high-resolution map.

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Need a GIS skills refresh? Sharpen your skills with this comprehensive spatial analysis challenge in ArcGIS Pro.

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Setting Up Your Workspace

By now, you should be familiar with file management protocols for GIS. In a typical workflow, you work on geospatial data using a local hard drive. When done, you compress your data and back up your work to your cloud storage so that you can retrieve the files from anywhere. For this tutorial, use the desktop as your local hard drive location.

On the computer desktop, create a project folder named Exploring_Errors. Be sure there are no spaces. You may use underscores instead of spaces. Create the following three subfolders inside this folder: original, working, and final.

Figure 1.1: This diagram represents a basic folder structure used in this book.