Using GIS and geographical data
Geography · Key Stage 3 · The School
Layers
A GEOGRAPHIC INFORMATION SYSTEM stores data in LAYERS that share a coordinate system: roads on one, rivers on another, population on a third, flood risk on a fourth. Because they line up, layers can be combined to ask questions no single map answers — which schools sit inside the flood zone, how many people live within a mile of a station.
Choosing the map
A CHOROPLETH shades areas by value and suits rates and densities. A PROPORTIONAL SYMBOL sizes a circle by value and suits totals. A DOT MAP shows distribution. Using a choropleth for totals is the classic error: it shades large rural areas dark simply because they are large, which tells you about area rather than about people.
Reading a map critically
The same data produces very different maps depending on the class boundaries chosen, the colours used, and whether totals or rates are shown. None of that is dishonest by itself, and all of it can mislead. Ask what is being measured, over what area, and what the classes are — a map with no legend and no source is a picture, not evidence.
Map the TOTAL cases by region and the cities glow red — because that is where the people are. Map cases PER 100,000 and the picture can invert completely, with a sparsely populated region turning out to have the highest rate. Neither map is false. One shows where the most patients are, which matters for hospital beds; the other shows where the risk is, which matters for control. Always check which you are looking at.