Introduction

Think about the last time you used a map on your phone to find a coffee shop or check how far you were from home. Beneath the blue dot, streets appeared in pale gray, parks in soft green, and water in familiar blue. You could read the map quickly because a cartographer had decided how thick to draw each street, how dark to make each building, and how faint to make each boundary. Those choices kept the background from competing with the place or route you needed to find. A well-designed basemap supports the information above it without drawing attention to itself.

In this activity, you will make those design decisions yourself. In January 2025, the Eaton Fire swept from the San Gabriel foothills into Altadena, a community just north of Pasadena. It became one of the most destructive wildfires in California history, damaging or destroying thousands of structures, most of them homes. Because Altadena is unincorporated, recovery and rebuilding are managed through Los Angeles County. You will act as a GIS analyst and build a structure-damage reference map for a county planning committee. The map will focus on the neighborhoods west of Lake Ave and south of Loma Alta Dr, where the losses were heaviest.

Nearly everything on the map you will make is part of the basemap. The structure damage data will appear above layers that show streets, buildings, parks, community boundaries, and the fire perimeter. The committee needs enough geographic context to locate a single property and see the broader pattern of damage, but the basemap should not compete with the damage data. You will control that balance through color, line weight, and typography.

Estimated time to complete this tutorial: 6 hours

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Setting Up Your Workspace

Before you begin working with the data, create a dedicated workspace for this project. A clear and consistent folder structure will help you stay organized as you move from data exploration to map design and final output.

Start by creating a new folder on your desktop and name it Eaton_Fire. Inside this main folder, make three subfolders:

original — for storing unaltered copies of your downloaded data.
working — for supporting files that are not stored in a geodatabase.
final — for completed products such as tables, reports, and final map layouts.

Folder tree showing an Eaton_Fire project folder with three subfolders named final, original, and working.

Figure 1: Create a local project workspace with three subfolders: original, working, and final. This structure gives downloaded source data, non-geodatabase supporting files, and completed deliverables predictable locations.

You will use this same folder structure at the start of each project to give each kind of file a predictable home. Downloaded source data goes in original, supporting files that do not belong in a geodatabase go in working, and completed deliverables go in final. ArcGIS Pro will store most new spatial datasets in the project geodatabase, which it creates during setup.

Caution: Create the Eaton_Fire project folder directly on the computer's desktop. Do not run the ArcGIS Pro project from Google Drive. Working there can cause errors while ArcGIS Pro reads or writes project files, resulting in failed tools or a corrupted project. When you finish working for the day or complete the activity, save the project and close ArcGIS Pro. Then upload the entire Eaton_Fire folder to Google Drive as a backup.

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Downloading the Project Data

For this activity, you'll need to download the data archive for the Mapping the Eaton Fire project using this link.

LA_Basemap_Data.gdb.7z — Google Drive

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This link will take you to a Google Drive download page. Download the file and copy it into your original folder.