Parameter adjustment magnitudes Already discussed satellite orbital motion Parameterized as initial conditions(C)at specific time and radiation model parameters For pseudo range positioning, broadcast ephemeris is often adequate. Post-processed orbits(GS)+3-5 cm (may not be adequate for global phase processing) Satellites orbits are easiest integrated in inertial space, but receiver coordinates are nearly constant in an Earth-fixed frame Transformation between the two systems is through the earth orientation parameters(EOP). Discussed in Lecture 4 04/17/02 12.540Lec18
04/17/02 12.540 Lec 18 6 Parameter adjustment magnitudes • Already discussed satellite orbital motion: Parameterized as initial conditions (IC) at specific time and radiation model parameters. • For pseudo range positioning, broadcast ephemeris is often adequate. Post-processed orbits (IGS) ±3-5 cm (may not be adequate for global phase processing). • Satellites orbits are easiest integrated in inertial space, but receiver coordinates are nearly constant in an Earth-fixed frame. • Transformation between the two systems is through the Earth orientation parameters (EOP). Discussed in Lecture 4
E○ P variations If analysis is near real-time, variations in polar motion and ut1 will need to be estimated After a few weeks these are available from IERS (+0. 2 mas of pole position, 0.05 ms UT1) in the ITRF2000 no-net-rotation system For large networks, normally these parameters are re-estimated. Partials are formed by differentiating the arguments of the rotation matrices for the inertial to terrestrial transformation 04/17/02 12.540Lec18
04/17/02 12.540 Lec 18 7 EOP variations • If analysis is near real-time, variations in polar motion and UT1 will need to be estimated. • After a few weeks, these are available from IERS (±0.2 mas of pole position, 0.05 ms UT1) in the ITRF2000 no-net-rotation system. • For large networks, normally these parameters are re-estimated. Partials are formed by differentiating the arguments of the rotation matrices for the inertial to terrestrial transformation
Position variations in trf frame The International Terrestrial Reference Frame(ITRF defines the positions and velocities of -1000 locations around the world(GPs, VLBl, slr and dOris Frame is defined to have no net rotation when motions averaged over all tectonic plates However, a location on the surface of the earth does not stay at fixed location in this frame: main deviations are: Tectonic motions(secular and non-secular) Tidal effects(solid earth and ocean loading Loading from atmosphere and hydrology First are normally accounted for 04/17/02 12.540Lec18
04/17/02 12.540 Lec 18 8 Position variations in ITRF frame • The International Terrestrial Reference Frame (ITRF) defines the positions and velocities of ~1000 locations around the world (GPS, VLBI, SLR and DORIS). • Frame is defined to have no net rotation when motions averaged over all tectonic plates. • However, a location on the surface of the Earth does not stay at fixed location in this frame: main deviations are: – Tectonic motions (secular and non-secular) – Tidal effects (solid Earth and ocean loading) – Loading from atmosphere and hydrology • First are normally accounted for
Solid earth tides Solid earth Tides are the deformations of the earth caused by the attraction of the sun and moon. Tidal geometry M R 04/17/02 12.540Lec18
04/17/02 12.540 Lec 18 9 Solid Earth Tides • Solid Earth Tides are the deformations of the Earth caused by the attraction of the sun and moon. Tidal geometry M* P l R r ψ