Map Skills, Cartography, Remote Sensing and GIS
Map Skills, Cartography, Remote Sensing and GIS
This domain tests map scale, direction, grid references, contours, projections, aerial photographs, remote sensing and GIS. Expect practical calculations and interpretation rather than definitions alone.
Core rules and concepts
- Scale is the ratio of map distance to ground distance. It may be a statement, a representative fraction (RF) or a graphical bar. A large-scale map shows a small area in detail (e.g. 1:10,000); a small-scale map shows a large area (e.g. 1:1,000,000).
- Latitude and longitude give absolute location; bearings give direction. Contours join points of equal height.
- Close contours mean steep slope; widely spaced contours mean gentle slope. A contour V pointing upstream marks a valley.
- Map projections transfer the curved earth to a flat surface and always distort shape, area, distance or direction.
- Remote sensing records energy reflected or emitted by objects. Passive sensors use sunlight; active sensors supply their own energy (radar). Resolution may be spatial, spectral, temporal or radiometric.
- GIS stores thematic layers and supports overlay, buffer and proximity analysis.
Worked example
On a 1:50,000 map, 4 cm represents 4 × 50,000 cm = 200,000 cm = 2 km. Reasoning: convert the map measurement to ground units using the RF, then convert centimetres to kilometres. If the same 4 cm spans six contour intervals of 20 m, the slope rises 120 m - steepness then depends on horizontal distance.
Traps
A large scale has a small denominator. Contour lines never cross. Optical remote sensing cannot see through thick cloud. GIS is not the same as GPS; GPS gives position, GIS analyses layers.