Great Britain National Grid

Description

This is a Transverse Mercator projected on the Airy spheroid. The origin is 49° N and 2° W. The central meridian is scaled to 0.9996012717. The value changed at version 9.2. The earlier value was 0.999601272. Because of this change, if two datasets have the different scale factor values, they are not considered equal. In version 9.3, the code was changed to treat both values as equivalent.

Learn more about Transverse Mercator projection

Projection method

Cylindrical, transverse projection with the central meridian centered along a particular region.

Lines of contact

Two lines parallel with and 180 km from the central meridian at 2° W.

Linear graticules

The central meridian.

Properties

Shape

Conformal; therefore, small shapes are maintained accurately.

Area

Distortion increases beyond Great Britain as the distance from the central meridian increases.

Direction

Local directions are accurately maintained.

Distance

Scale is accurate along the lines of secancy 180 km from the central meridian. Scale is compressed between them and expanded beyond them.

Limitations

Suitable for Great Britain. Limited in east–west extent.

Uses and applications

The national coordinate system for Great Britain; used for large-scale topographic mapping.

Parameters

Workstation

• Projection-specific parameters are set by the software.