[Proj] The world of ECEF aka geocentric coordinates
Duncan Agnew
dagnew at ucsd.edu
Sat Jan 31 17:36:29 EST 2009
Bomford 4th edition, Appendix C gives the iterative formula, along with
Bowring's approximation (adequate
on the Earth's surface). Pace Cliff, he uses "spheroid" for the generic
surface, but restricted to flattened
ellipsoids rather than elongated ones (definition in Appendix A).
ECEF has meaning as a reference frame--Earth Centered Earth Fixed--but
has no bearing on the types of coordinates used to denote a particular
position--they might be spherical, ellipsoidal, or Cartesian. Strictly
speaking, "geocentric" would be a subset of ECEF, since the reference
frame used for satellite
orbits is also geocentric, but (partly) tied to inertial space rather
than to the (average) Earth for its
orientation.
All the conversions being discussed are between coordinate triplets
(Cartesion and ellipsoidal), and
have nothing to do with the reference frame, save that its origin is at
the center of mass of a uniform
ellipsoid, and polar axis along its axis of symmetry. Maybe the
conversion should just be labeled by
coordinate type?
Duncan Agnew
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