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Reference · printable (Ctrl/Cmd+P)
QGIS cheat sheet.
The interface, in one breath
Middle: the map canvas. Bottom-left: the Layers panel — your map is this list, drawn bottom-to-top. Top: toolbars (hover anything for its name). Bottom edge: coordinates, scale, and the current CRS.
Vocabulary
| Word | Meaning |
|---|---|
| Layer | One dataset on the map — points, lines, polygons, or an image. Maps are stacks of layers. |
| Feature | One thing in a layer: one station, one ward. Every feature is also a row in the attribute table. |
| Attribute table | The spreadsheet behind a layer. Right-click layer → Open Attribute Table. |
| Symbology | How a layer looks: colors, sizes, categories. Double-click a layer to edit it. |
| CRS | Coordinate reference system — how the round Earth becomes a flat map. Accept defaults until Session 2. |
| GeoJSON | A simple text file format for layers. What we publish; what QGIS happily reads and writes. |
| Vector vs. raster | Vector = shapes with data (our world). Raster = pixel grids like satellite imagery. |
The moves
| You want to… | Do this |
|---|---|
| Add data | Drag the file onto the QGIS window. That's genuinely it. |
| See everything | Right-click layer → Zoom to Layer(s). |
| Restyle a layer | Double-click it → Symbology. "Categorized" + a column + Classify = color by data. |
| Label features | Double-click layer → Labels → Single Labels → pick the column. Add a text buffer. |
| Inspect one feature | Identify tool (blue “i” icon), then click the feature. |
| Reorder drawing | Drag layers up/down in the Layers panel. Top of list = front of map. |
| Make a finished map | Project → New Print Layout → Add Map, Add Label → Export as Image. |
| Save your work | Project → Save. A .qgz project remembers layers + styling (not the data files — keep them together). |
| Export a layer | Right-click layer → Export → Save Features As → GeoJSON, CRS EPSG:4326 — the Atlas format. |
| Undo a mess | Ctrl/Cmd+Z works nearly everywhere. Worst case: remove the layer and drag it in again. |
Where data lives
| Source | What's there |
|---|---|
| opendata.dc.gov | Hundreds of DC datasets — wards, transit, housing, trees, permits. Export as GeoJSON. |
| data.census.gov | Demographics for joins (Session 2). TIGER files carry the shapes. |
| naturalearthdata.com | Countries, states, rivers, cities for world/regional maps. Public domain. |
| guspatial.org/atlas | Our published layers — every atlas's data/ folder is downloadable GeoJSON. |