Read the world. Make a map.

A map is a set of decisions made visible. Someone chooses the question, the frame, the places worth labeling, the date of the evidence, and the things to leave out. Learning cartography means learning to notice those choices and make your own responsibly.

This independent University of El Segundo course moves from reading historical maps to creating a small, reproducible local study. Six lessons introduce the essential ideas; a capstone asks what public libraries and parks lie within a declared 25-mile study radius. The suggested schedule is roughly nine to ten hours including the project. No previous GIS experience is required.

Lesson 1: Ask what the map is for

Proposed time: 45 minutes.

Maps have served many purposes, including orientation, navigation, administration, and storytelling. The British Museum’s Babylonian Map of the World represents a world surrounded by water, with Babylon and other places identified. Read it as evidence of a particular understanding of the world. Avoid treating it as an unsuccessful modern road map. British Museum collection record ↗

Move to Los Angeles. The Library of Congress catalogs H. B. Elliott’s 1891 view and B. W. Pierce’s 1894 view as perspective maps without a uniform scale. Their viewpoints and selected landmarks make them useful for interpreting how the city was pictured, but unsuitable for calculating street distances. 1891 view ↗, 1894 view ↗

Outcome: identify audience, purpose, evidence, and omission. Exercise: compare one historical view with a present-day topographic map. Write five observations and two questions that the images cannot answer. Keep an observed feature separate from an explanation you have inferred.

Lesson 2: Understand coordinates, projection, and scale

Proposed time: 60 minutes.

Latitude and longitude describe angular position. A coordinate reference system adds the framework needed to interpret coordinates, including a datum. A projection represents the curved Earth on a flat surface. Different projections preserve different properties; none preserves every distance, area, shape, and direction everywhere. Choose for the task and location. USGS projection manual ↗

Scale connects map distance to ground distance. At 1:24,000, one inch represents 24,000 inches, or 2,000 feet. A large-scale map shows a smaller area in greater detail. Zooming an old or coarse dataset does not improve the observations behind it. USGS topographic mapping ↗

In QGIS, inspect each layer’s source CRS and the project CRS. Assigning a CRS tells software what existing numbers mean; reprojection transforms those numbers. Changing a label cannot fix incorrectly interpreted coordinates. QGIS CRS guide ↗

Outcome: explain these distinctions. Exercise: inspect two differently projected layers, record their units, and explain how QGIS can display them together.

Lesson 3: Build an evidence trail

Proposed time: 75 minutes.

Begin with a small source inventory. For every layer record its publisher, link, date or vintage, geographic coverage, coordinate system, license, and known limitations. Check a sample of features against an independent official source. A missing feature may indicate incomplete collection, a classification choice, or an outdated record.

Use Census TIGER/Line for geographic features and boundaries. Its core files contain geographic identifiers but do not themselves include demographic statistics. Match geographic units and vintages before joining a statistical table. Census TIGER/Line ↗

OpenStreetMap is a collaboratively maintained database with attribution and licensing obligations. The database license and permission to use a particular tile server are separate questions. Do not assume the public tile service is an unlimited hosting service. OSM copyright ↗, tile policy ↗

Outcome: evaluate fitness for purpose. Exercise: build a three-source register. If adding American Community Survey estimates, retain their margins of error and avoid treating a small difference as a reliable ranking. Census uncertainty guidance ↗

Lesson 4: Design a map people can read

Proposed time: 75 minutes.

Give the main question the strongest visual emphasis. Keep contextual streets and boundaries quieter than the subject. Use a clear title, readable labels, a legend that explains actual symbols, a useful scale indicator, source dates, and a concise limitations note. Show orientation when it matters, especially if north is not at the top.

Use distinct shapes or labels as well as color. Separate “no data” from zero. If mapping regional statistics, choose rates or densities when the question concerns relative prevalence; raw totals answer a different question. Explain class breaks because different groupings can change the apparent pattern.

Accessibility is part of the information design. Provide a short image description and an adjacent longer explanation of the map’s key findings. For interactive maps, also provide a usable list or table of places, keyboard-operable controls, and visible focus. W3C color guidance ↗, complex-image guidance ↗

Outcome: communicate without depending on color or pointer interaction. Exercise: test your draft in grayscale and at phone width, then ask another reader to find one place and explain the legend.

Lesson 5: Make the El Segundo study

Proposed time: 90 minutes.

Define the origin before drawing anything. The 2025 Census Gazetteer lists El Segundo’s representative internal point at latitude 33.910367, longitude −118.425079. It is a reference point for the geographic entity, not City Hall, a library entrance, or a population center. Document the source and verify its coordinate reference information before analysis. California Gazetteer ↗, field definitions ↗

Twenty-five statute miles equals 40,233.6 meters. Great-circle distance measures the shortest surface path on a spherical Earth model; an ellipsoidal geodesic uses an ellipsoid. Road distance follows a network. Travel time additionally depends on travel mode, speeds, restrictions, and conditions. A radius therefore cannot establish a 25-minute service area.

Use verified public-facility coordinates, document the earth model and method, and inspect features near the boundary. A centered azimuthal-equidistant workflow or geodesic calculation can support the radius exercise; a Web Mercator screen circle is insufficient. PROJ projection documentation ↗

Outcome: make the spatial rule reproducible. Exercise: create the radius and an inclusion table, flag uncertain locations, and explain why a site’s entrance can differ from its mapped center.

Lesson 6: Share the result responsibly

Proposed time: 45 minutes.

QGIS supports the desktop analysis workflow. MapLibre GL JS can display GeoJSON in a browser through sources and styled layers. It is a renderer: the choice of data, basemap, hosting, and update process still belongs to the mapmaker. A teaching example can use local data without a vendor account or map key. MapLibre GeoJSON source ↗

For web exchange, RFC 7946 GeoJSON uses WGS 84 decimal degrees, with longitude before latitude. Transform appropriately rather than merely renaming a CRS. Coordinate decimal places alone do not establish positional accuracy. GeoJSON standard ↗

Publish source links, credits, dates, a text alternative, and the limits of the analysis alongside the map. Use public facilities for this exercise. Do not collect household locations, individual movement histories, or personal attendance records. Aggregated statistics should not become claims about a particular person.

Outcome: package a map someone else can inspect. Exercise: have a reviewer identify one supported conclusion and one tempting conclusion that the evidence does not support.

Capstone: A public-places atlas within 25 miles

Proposed time: 2.5–3 hours.

Build a small atlas answering one question: which verified public libraries and parks fall within the declared radius? Begin with the official listings for El Segundo Public Library at 111 West Mariposa Avenue, Library Park on the 600 block of Main Street, and Recreation Park at 401 Sheldon Street. These addresses are starter records, not a verified coordinate dataset. Library ↗, Library Park ↗, Recreation Park ↗

Add five to ten public sites from official sources across the study area. Verify coordinates and public access separately; a location record does not establish today’s opening hours. Submit the map, a matching accessible place list, the source register, and a 250-word methods note. Explain the origin, units, distance model, collection date, exclusions, and uncertainty. Include one observation, one limitation, and one next question.

A successful project is readable and reproducible. An honest “location still unverified” is stronger evidence work than a confident-looking invented pin.