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The British National Grid (BNG)
•The
British National Grid (BNG) is based on the National Grid System of England,
administered by the British Ordnance Survey. The true origin of the system is
at 49 degrees north latitude and 2 degrees west longitude. The false origin is
400 km west and 100 km north. Scale at the central meridian is 0.9996. The
first BNG designator defines a 500 km square. The second designator defines a
100 km square. The remaining numeric characters define 10 km, 1 km, 100 m, 10
m, or 1 m eastings and northings.
Transverse Mercator
Transverse Mercator
•Transverse Mercator projections result from
projecting the sphere onto a cylinder tangent to a central meridian. Transverse
Mercator maps are often used to portray areas with larger north-south than
east-west extent. Distortion of scale, distance, direction and area increase
away from the central meridian.
•Many national grid systems are based on the
Transverse Mercator projection
Oblique Mercator
•Oblique Mercator
•Oblique Mercator projections are used to
portray regions along great circles. Distances are true along a great circle
defined by the tangent line formed by the sphere and the oblique cylinder,
elsewhere distance, shape, and areas are distorted. Once used to map Landsat
images (now replaced by the Space Oblique Mercator), this projection is used
for areas that are long, thin zones at a diagonal with respect to north, such
as Alaska State Plane Zone 5001.
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