| libgeo-helmerttransform-perl | Transformations between coordinates in different datums | Mehr ... |
It is usual to describe geographical points in terms of their polar coordinates
(latitude, longitude and altitude) referenced to a "datum ellipsoid", which is
used to approximate the Earth's geoid. The latitude, longitude and altitude of
a given physical point vary depending on which datum ellipsoid is in use.
Unfortunately, a number of ellipsoids are in everyday use, and so it is often
necessary to transform geographical coordinates between different datum
ellipsoids.
.
Two different datum ellipsoids may differ in the locations of their centers, or
in their shape; and there may be an angle between their equatorial planes or
the meridians relative to which longitude is measured. The Helmert Transform,
which this module implements, is a linear transformation of coordinates between
pairs of datum ellipsoids in the limit of small angles of deviation between
them. |
