Map Work and Geographical Skills: Grid References, Scale, Direction and Symbols
Grid references
Topographic maps are crossed by eastings (vertical lines, numbered left to right) and northings (horizontal lines, numbered bottom to top). A four-figure reference names a whole square, while a six-figure reference locates a point within it. Always give the easting first and the northing second.
Scale
Scale links map distance to ground distance. A scale of 1:50 000 means 1 unit on the map represents 50 000 of the same units on the ground, so 1 cm = 0.5 km and 4 cm = 2 km. Scale may be shown as a ratio (1:50 000), a word statement ("2 cm represents 1 km") or a linear bar. Large-scale maps such as 1:50 000 show more detail over a small area; small-scale maps such as 1:1 000 000 show less detail over a large area.
Direction and bearing
Use a compass rose with 16 points (N, NNE, NE, ENE, E …). A bearing is measured in degrees clockwise from north, so east is 090°, south 180° and west 270°. Give back-bearings as the opposite direction.
Symbols and relief
Learn the legend: trigonometrical stations, spot heights, contours, rivers, perennial and seasonal streams, roads, railways, mission stations, clinics, dams. Contours join points of equal height, usually at a contour interval of 20 m. Contours close together mean a steep slope; far apart mean gentle; a V pointing uphill marks a valley, a V pointing downhill marks a spur.
Trap: the commonest error is reading the northing before the easting, or using a four-figure reference when the question asks you to pinpoint a school or bridge.
Rule of thumb: "walk along the corridor before climbing the stairs" - eastings first, then northings.