CARTESIAN TO TOPOCENTRIC |
An alternative formulation for two-dimensional coordinates is a local
topocentric system. The horizontal plane is tangential at a point
with Cartesian coordinates ( Xo,Yo,Zo
). The ( E,N,H ) components form a right-handed system.
The Cartesian coordinates can be converted to local topocentric components
using the relation (SEEBER, 1993):
 |
(11.1-16a) |
where the rotation matrix T is given by:
 |
(11.1-17) |
The converted VCV matrix can be calculated from:
| VCVENH = T . VCVXYZ . TT | (11.1-18) |
This relation is very useful for converting GPS results to a form that can be used to compute 2-D relative error ellipses. In Australia, the semi-major axes of the relative error ellipses can be tested in order to check if the GPS survey has satisfied the requirements for a certain ORDER of GPS survey (section 10.2.3).
Back to Chapter 11 Contents
/ Next Topic / Previous Topic
© Chris Rizos, SNAP-UNSW, 1999