Map Reading, Interpretation and Practical Geography
Map reading tests scale, direction, contours, bearings, topographical sheets and simple statistical mapping. Practical Geography also includes basic GIS and remote sensing ideas. Accuracy in units and interpretation matters more than lengthy description.
Scale and direction
- Representative fraction (RF) is unitless, such as 1:50,000. A statement scale gives a ground unit, such as 1 cm to 0.5 km. A graphical scale survives enlargement or reduction.
- To convert map distance to ground distance, multiply by the denominator and convert centimetres to kilometres.
- Grid north, true north and magnetic north differ. Magnetic declination is the angle between true north and magnetic north.
Contours and bearings
Contour interval is the vertical distance between successive contours. Index contours are thicker and labelled. Close contours mean steep slope; widely spaced contours mean gentle slope. A contour V pointing upstream indicates a valley. A prismatic compass measures magnetic bearings; a plane table is used for field mapping.
Worked example
On a 1:50,000 map, 4 cm represents 4 × 50,000 cm = 200,000 cm = 2 km. If a slope rises 20 m over that 2 km, gradient = 20 ÷ 2,000 × 100 = 1%. The reasoning is to convert both rise and run to the same unit before dividing.
GIS and statistical maps
GIS stores layers of spatial data; remote sensing records energy reflected or emitted from the surface. Choropleth maps show density or ratio by area; isopleths join equal values; dot maps show distribution; pie and bar graphs compare quantities.
Traps
RF has no unit. Do not mix contour interval with index contour. A V points upstream, not downstream. Check whether a bearing is magnetic or true. Convert cm to km correctly.