Height clues on a topographical map

Height clues on a topographical map

Benchmarks

Spot heights

Trigonometric beacons

Contour lines

We will discuss the following four ways of showing height on a map:

Contour lines are brown lines on a topographic map. Each contour line connects places that are the same height above sea level. The contour interval is 20 meters on 1:50 000 topographic maps. Not every contour line is numbered. Every fifth contour line is shaded darker. These darker contour lines show the height 100 meters apart. By counting the darker lines, we can calculate the height of the hill or mountain. The numbers on the contour lines help you see if a slope is sloping up or down.

Contour Lines

Spot heights show the exact height of a place in metres, as a number next to a dot, marked on the map. Spot heights on a map are often shown on top of hills.

Spot heights

Also known as 'trig' beacons - are like spot heights. They show points on the land for which an exact height is known. Trig beacons are marked by a little triangle. The number gives the height as a decimal, for example 1 003.1. This place is 1003 metres and 10 centimetres above sea level.The number in italics is the number of the trig beacon.

Trigonometric Beacons

The whole of South Africa is mapped using trig beacons. They are actual beacons that can be found in real life.

Trig beacons in real life

Like spot heights and trig beacons, benchmarks are also points for which the exact height is known. Benchmarks are shown on maps as a number and arrow, usually next to the road. Benchmarks show height in metres as decimals, for example 436.1.

Benchmarks

VIDEO: height clues on a map.

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