IGS Analysis Center Workshop - IGS - NASA

IGS- and the COM-sets, but that the transformation parameters are very small, too (see Table 3.2).Table 3.2 Transformation parameters between the COM and IGS Combined OrbitsMMJDDTdaysDX(m)DY(m)DZ(m)RX RY RZ SCALE RMS .(mas) (mas) (mas)(m)49004.049005.049006.049007.049008.049009.049010.049011.049012.049013.049014.049015.049016.049017.01.01.01.01.01.01.01.01.01.01.01,01,01.01.0-.003.008.006-.003.001.005.005-.003.000-.004-.005.003.000.004.004-.001-.003-.010.001-.008-.010-.011-.003-.005.000-.004-.004-.009.015.007.019.010.008.015.001.010.002.013.002.016-.002-.003-. 1 -. 2 .0.0 .0 .0.0 .0 .1.0 .1 .1.0 .0 .2.0 .1 .5.0 .0 .2.0 .0 .6.0 .1 .2.0 .0 .0.0 .0 .0.0 .2 -.1.0 .1 -.2.0 .2 -.2.1-.4-.4-.5-. 5-.3-.3-.4-. 5-. 3-. 3-.2-. 3-. 3.09.06.05.05.04.07.05.05.05.05.05.06.06.06COM IGSCOM IGSCOM IGSCOM IGSCOM IGSCOM IGSCOM IGSCOM IGSCOM IGSCOM IGSCOM IGSCOM IGSCOM IGSCOM IGS------------------------------------------------------- ----------------------------------------------------------Mean 14.0 .001 -.005 .008 .0 .0 .1 -.3 .06 COM IGSRMS of Mean .001 .001 .002 .0 .0 .1 .0 .004.1 North American baselines4. BASELINE TESTSThe IGS and COM combined orbits along with the COD, EMR and GFZ orbits were used in GPSbaseline processing tests. The first part of the test concentrates on the orbits above North Americaand involves four Canadian sites ALGO, DRAO, STJO and YELL. A double difference softwarewas used for this test. The three baselines considered here are originating from station ALGO andare between 2000km and 3000km long. Each day was processed independently usipg phaseobservations only and solving for initial cycle ambiguities. In all cases the orbits were held fixedand identical data, options etc. were used for the five solutions each day. The only differencebetween the runs for a particular day was the orbit used. To check on both the orbit precision andthe reference frame stability implied by the orbits, no Helmert transformation was used. In this waythe orientation changes as well as regional orbital errors should be reflected in the latitude,longitude and height variations. The reference scale changes should also be seen in the baselinelength variations. These variations can be effectively removed by Helmert transformations andinter orbit comparisons beeome difficult. In fact the reference frame stability as well as increasedprecision are two main reasons why precise orbits are used. In addition to the already mentioned50