Cartography: Maps, Scales and Projections
Core concepts
Cartography is the science of map design and representation. Know scale types (representative fraction, verbal, graphic) and conversions; large-scale maps show small areas in greater detail. Understand map projections: cylindrical, conic, azimuthal; and their properties (conformal, equal-area, equidistant, azimuthal). Mercator is conformal but distorts area at high latitudes; Peters is equal-area; Robinson is a compromise. Know grid systems: latitude, longitude, great circles, and the Universal Transverse Mercator zones. Study map elements: title, legend, scale bar, north arrow, graticule, and inset. Understand relief representation: contours, hachures, spot heights, and hill shading; and interpret contour patterns for slope, valley, ridge, and cliff. Also cover surveying basics, chain and compass survey, plane table, and modern digital cartography with GIS.
Traps
Students often convert scales incorrectly, forgetting that 1:50,000 means 1 cm = 0.5 km. Do not assume Mercator preserves area; it does not. A common error is reading contour spacing as elevation rather than slope. Remember that a representative fraction is unitless, so it is valid in any measurement system.
Worked example
A map has scale 1:25,000. A rectangular field measures 4 cm by 6 cm. Find its area in hectares. Rule of thumb: convert each side to ground units first. 4 cm x 25,000 = 100,000 cm = 1 km; 6 cm x 25,000 = 150,000 cm = 1.5 km. Area = 1.5 km = 150 hectares (1 km = 100 ha).