Geography - maps, graphs

4-digit grid reference

A grid reference used to identify a general area on a topographic map. Eastings are read first, followed by northings.

6-digit grid reference

A more precise grid reference used to identify an exact location. Eastings are read first, followed by northings.

Area reference

A reference used to identify a general area or grid square on a map.

Bearing

A direction measured clockwise from north using three figures, from 000° to 360°.

Aspect

The direction that a slope faces.

Gradient

The steepness of a slope, calculated as vertical rise divided by horizontal distance, often expressed as a ratio or percentage.

Relief

The difference in elevation between the highest and lowest points of an area.

Contour line

A line joining points of equal elevation above sea level.

Spot height

A precisely surveyed point showing the exact elevation of a location.

Cross-section

A side-on representation of the shape and relief of the landscape along a particular line.

Vertical exaggeration

The amount by which the vertical scale of a cross-section is enlarged compared with the horizontal scale.

Line of sight

The ability to see directly from one location to another without the view being blocked by terrain.

Isobar

A line on a weather map joining places with equal atmospheric pressure.

Weather map

A map showing atmospheric conditions such as pressure systems, fronts, winds and other weather information.

High-pressure weather

Generally associated with sinking air, clear skies, lighter winds and dry conditions.

Low-pressure weather

Generally associated with rising air, cloud formation, precipitation and stronger or more variable winds.

Population density

The number of people living per unit of land area, usually expressed as people per square kilometre.