🗺️ Cartography

What you’ll learn

1. The Map Became a DatabaseEstablish the course through-line: a modern digital map is a queryable database of the world, not a fixed drawing, and the visible image is one rendering computed on demand.Unlike a paper map's frozen image, a digital map stores the world as data with coordinates and renders a temporary picture for each view and query. This shift from artifact to database — traced from Mercator (1569) to GIS (1963) to OpenStreetMap (2004) and web maps (2005) — is what changes what a map can do, who can make one, and what it knows about you.
2. Two Ways to Store the World: Vector and RasterDistinguish the two fundamental ways to encode geography as data — vector (objects with attributes) and raster (a grid of cell values) — and when each is appropriate.Vector data stores discrete objects (points, lines, polygons) with coordinates and attributes, staying sharp at any zoom and 'knowing' what things are; raster data is a grid of cells (imagery, elevation) that captures continuous surfaces but pixelates and carries no identity. Real maps blend both: raster for how the world looks, vector for what it is.
3. Web Mercator: The Projection the Whole Internet ChoseExplain coordinate reference systems and why web mapping standardised on Web Mercator (EPSG:3857) despite its large area distortion.Coordinates are meaningless without a shared reference system; WGS 84 gives global latitude/longitude, but flat screens require a projection. Web maps chose Web Mercator (EPSG:3857) because it turns the globe into a fast, tileable square — at the cost of inflating high-latitude areas, so Greenland (~2.2M km²) looks nearly as large as Africa (~30.4M km², about 14x larger).
4. The Slippy Map: How Tiles Move the World to Your ScreenExplain the slippy-map tile scheme — 256-pixel tiles addressed by zoom/x/y in a pyramid — and why pre-rendering and caching make live web maps efficient.Web maps are built from 256-pixel square tiles: each zoom level quarters a tile's area and quadruples their count, so only the tiles covering your screen are fetched. Because a tile at a given address is identical for everyone, it is pre-rendered once and cached worldwide, making live maps cheap to serve; the trade-offs are fixed resolution and dependence on the Mercator square (newer vector tiles ship data instead of pictures).
5. Spatial Analysis: The Real Superpower of GISIntroduce spatial analysis — overlay, buffers, spatial joins, and distance queries — as the ability of a GIS to compute new answers from map data, and the data-quality caveat.Because a GIS stores maps as data, it can derive answers no layer shows alone: overlay/intersection (which homes lie in the flood zone), buffers (within 400 m of a bus stop), spatial joins (tag each point with its district), and nearest/distance queries. The catch is that analysis looks authoritative regardless of input quality, so knowing each layer's age, accuracy, and coordinate system is the real skill.
6. Thematic Maps and the Honest ChoroplethTeach how thematic maps, especially choropleths, can mislead through un-normalised counts, classification choices, and colour schemes — and the honest practices that counter it.Choropleths shade regions by value and are easy to fake without false numbers: mapping raw counts usually just redraws population, so values must be normalised; and binning method (equal interval, quantile, Jenks) plus colour scheme can flip the story. Honest thematic mapping states its rate, classes, and method and uses sequential/diverging (never rainbow) colour-blind-safe ramps.
7. Who Draws the World NowExplain crowd-sourced cartography through OpenStreetMap — its open, editable database model, its scale and impact, and its inherited biases.Founded by Steve Coast in 2004, OpenStreetMap made the world map a free, editable database anyone can extend, with edits entering immediately and no central review; it now has more than ten million contributors and underpins many apps and companies. But an open map reflects who shows up — richer where volunteers are and skewed toward their interests — so it swaps the state's biases for the crowd's.
8. The Map That Watches BackExamine the ethics of the live, personal map: location data as a two-way instrument, the difficulty of truly anonymising location trails, and practical controls.A live map needs your position to work, making location a two-way instrument that answers your questions and emits a revealing trail others can analyse; this data economy often pays for 'free' maps. Location trails are near-fingerprint unique and hard to truly anonymise, so the goal is informed use — location-while-in-use, disabling ad IDs, clearing history — not abstinence.

Questions this course answers

Grounded in trusted sources

• Geographic information system — Wikipedia: https://en.wikipedia.org/wiki/Geographic_information_system
• Web Mercator projection — Wikipedia: https://en.wikipedia.org/wiki/Web_Mercator_projection
• Mercator projection — Wikipedia: https://en.wikipedia.org/wiki/Mercator_projection
• The true size of Greenland (~2.2M km² vs Africa ~30.4M km², ~14x) — Visual Capitalist: https://www.visualcapitalist.com/true-size-of-greenland-map-mercator-projection/
• Tiled web map — Wikipedia: https://en.wikipedia.org/wiki/Tiled_web_map
• Spatial analysis — Wikipedia: https://en.wikipedia.org/wiki/Spatial_analysis
• Choropleth map — Wikipedia: https://en.wikipedia.org/wiki/Choropleth_map
• OpenStreetMap (founded 2004; 10M+ contributors) — Wikipedia: https://en.wikipedia.org/wiki/OpenStreetMap

Every Wunder lesson is built from real, reputable sources — never invented.

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