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Glossary M

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Map Projection

A wide range of map projections have been developed to try to portray the curved surface of the Earth on a flat piece of paper. This cannot be done accurately so any map will contain some distortion, but different projections have different advantages. For example, some of them portray relative distances accurately, whereas others display relative areas better. Note that the distortion will be greater the larger the area of the Earth's surface portrayed.

Map Scale

Map scale refers to the extent to which reality is reduced to display it on a map - for example, a scale of 1:25,000 means that 1 centimetre on the map represents 25,000 centimetres (250 metres) on the ground. Large scale maps (for example, 1:1,250 or 1:2,500) show a small area of the Earth's surface in a lot of detail. Small scale maps however (for example, 1:1,000,000) show large areas in very little detail.


OS MasterMap is Ordnance Survey's intelligent digital map of Great Britain. It contains a wide range of different layers of mapping data and is designed for use with geographic information systems (GIS) and database systems. OS MasterMap is the branded product of the Digital National Framework (DNF).
Further information about OS MasterMap.

Metropolitan County

The six metropolitan counties were administrative areas in England from 1974 to 1986, forming the upper tier of a two-tier local government structure. They were subdivided into metropolitan districts but when the metropolitan county councils were abolished in 1986 the district councils became unitary administrations. The metropolitan county areas are still used for statistical purposes however.
Further information on Metropolitan Counties and Districts.

Metropolitan District

The 36 metropolitan districts are subdivisions of the six metropolitan county areas of England. Since the abolition of the metropolitan county councils in 1986 the metropolitan district councils have been unitary administrations.
Further information on Metropolitan Counties and Districts.

Content from the Office for National Statistics.
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