Introduction

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.

Estimated time to complete this tutorial: 6 hours

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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.

A diagram representing the standard folder structure.

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

Setting up a Project in ArcGIS Pro

When creating a new project, there are a couple of ways to define your workspace in ArcGIS Pro. You can either create your workspace at the same time as the project or define an existing workspace for the project to use. In this example, you will define the folder Exploring_Errors that you just created on the desktop as the project workspace for ArcGIS Pro.

Why is this important? The tools in ArcGIS Pro will default their outputs to locations within the workspace you designate. This behavior helps to keep track of GIS files, which are easily lost.

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Open ArcGIS Pro. If it is your first time working in ArcGIS Pro, you may be prompted to sign in (Figure 1.2).

ArcGIS Pro Sign in options.

Figure 1.2: Follow the prompts under “Your ArcGIS organization’s URL.”

On the ArcGIS Pro home page, click “Map” under the new project options (Figure 1.3).

ArcGIS Pro New Project options.

Figure 1.3: The Map template is one of the standard options for creating a new project in ArcGIS Pro.

When the Create New Project window opens, name the project Exploring Errors. Spaces are OK in this instance. The next two steps are important, so don’t skip them. Click the file folder icon so that the location is set to your Exploring_Errors folder on the desktop. Then uncheck the box next to Create a new folder for this project (Figure 1.4). You don’t need to create a new folder since it would be redundant.

ArcGIS Pro Create a New Project options.

Figure 1.4: Be sure that your settings match this image.

When you create a project in ArcGIS Pro, several elements are added automatically to your workspace files. In Windows File Explorer, open your workspace folder to see what is inside (Figure 1.5). You should notice that beyond the three subfolders you initially created (original, working, and final), there are a few other items added to your workspace.

A view of the workspace folder as seen in Microsoft Windows File Explorer.

Figure 1.5: Each new project in ArcGIS Pro comes with several default files and folders.

The folder Exploring Errors.gdb is actually a file geodatabase. You should also see an ArcGIS project file with the same name. There are a few other items created. It is important that you do not delete or move any of these items, or you run the chance of corrupting your project.