Cartography and Spatial Skills: Scale, Grid and GIS
Cartography and Spatial Skills tests map interpretation, scale, coordinates and basic GIS reasoning. Most marks are lost on units and direction, not on difficult theory.
Core rules
- Scale: map distance ÷ ground distance. A 1:50,000 map means 1 cm represents 0.5 km; convert units before calculating. Large-scale maps (1:10,000) show more detail; small-scale maps (1:1,000,000) show more area.
- Grid references: eastings first, then northings; read to the nearest tenth for a six-figure reference. Contours: interval is the vertical difference between adjacent lines; closer contours mean steeper slope.
- Coordinates: latitude measures north–south of the equator; longitude measures east–west of Greenwich. Degrees, minutes, seconds; 1° = 60 minutes.
- GIS: vector data use points, lines and polygons; raster data use cells. Layers can be overlaid; buffer, overlay and proximity analysis answer spatial questions.
Worked example
On a 1:25,000 map, two points are 7.2 cm apart. Ground distance = 7.2 × 25,000 cm = 180,000 cm = 1.8 km. If a straight road is walked at 4 km/h: 1.8 ÷ 4 = 0.45 h = 27 minutes. Show the conversion; do not write 1.8 cm or 180 m.
Traps
Do not mix centimetres and kilometres without converting. Do not read northings before eastings. Do not assume the contour interval from the legend if the question states it. Do not confuse magnetic north with grid north.
Key points
- Scale = map distance ÷ ground distance; convert units first.
- Large-scale maps show detail; small-scale maps show area.
- Grid references are eastings then northings.
- Closer contours indicate steeper slopes; contour interval is the vertical gap.
- Vector uses points, lines and polygons; raster uses cells.