This transverse cylindrical projection, maintains scale along the central meridian and all lines parallel to it, and is neither equal-area nor conformal. It is most suited for large scale mapping of areas predominantly north-south in extent.
Method of Projection - Transverse Cylinder:
A transverse cylinder is projected onto the globe conceptually, and is tangent along the central meridian. Cassini is analogous to the Equirectangular projection in the same way that the Transverse Mercator is to the Mercator projection. This projection may also be referred to as the Cassini-Soldner, since ArcView actually uses the formulae based on the more accurate ellipsoidal version developed in the 19th Century.
Point of Tangency:
Conceptually a line, specified as the central meridian.
Linear Graticules:
The Equator, central meridian, and each meridian 90 degrees from the central meridian.
Properties:
Shape:
No distortion along the central meridian. Distortion increases with distance from the central meridian.
Area:
No distortion along the central meridian. Distortion increases with distance from the central meridian.
Direction: Generally distorted.
Distance: Scale distortion increases with distance from the central meridian; however, scale is accurate along the central meridian and all lines perpendicular to the central meridian.
Limitations:
Should be used primarily for large scale mapping of areas near the central meridian. Transverse Mercator often preferred because of difficulty measuring scale and direction on Cassini. Since the scale is constant along any straight line on the map that is parallel to the central meridian, the projection is more suitable for regions that are north-south in extent than for regions extending in other directions.
The projection is neither equal-area nor conformal, but is a compromise of both features.
Uses and Applications:
Formerly used by the Ordnance Survey in Great Britain. Still used in Cyprus, Czechoslovakia, Denmark, Germany, and Malaysia.
