Reference Frame of BKGI
Bundesamt für Kartographie und Geodäsie
in cooperation with
Geodetic Institute of the University of Bonn
The BKG VLBI Analysis Centre in cooperation with the VLBI group at the University of Bonn computed this VLBI global combined solution [RSC (BKGI) 02 R 01] . For it, a worldwide set of VLBI observations over the period January 1984 - December 2001 has been processed with the software CALC 9.12/SOLVE release 2001.12.21. The orientation of the celestial frame has been defined by constraining to zero the sum of the right ascension and declination adjustments of the ICRF defining sources in RSC (BKGI) 02 R 01. Tropospheric gradients have been estimated in the solution.
Reference Frame Characteristics :
Table 1 gives the number of sources and their mean standard error of this Reference Frame according to following classification :
- "defining", "candidate" and "other" sources correspond to the classification of ICRF sources,
- "new" are the sources added in ICRF-Ext.1,
- "additional" is for sources not present in ICRF-Ext.1 and observed in this VLBI program.
Total Defining Candidate Other New Additional N N m N m N m N m N m 594 209 0.13 216 0.13 102 0.04 44 0.24 23 0.76
Table 1 : N = number of sources, m = mean standard error (Unit: mas).
Comparison of this celestial frame to ICRF-Ext.1 :
Under the assumption that ICRF-Ext.1 is free from deformations, the systematic effects detected in the comparison indicate the existence of deformations in the individual frame.
The algorithm of comparison is the one currently used at the ICRS Centre; the coordinate difference between two frames is modelled by a global rotation of the axes, represented by the three angles A1, A2, A3, and by a deformation represented by three parameters : two slopes (Da) and (Dd), and one bias (Bd).
Table 2 gives the global orientation between axes of this catalogue and those of the ICRS.
N A1 A2 A3 ra rd 209 +0.036±0.016 +0.004±0.016 -0.053±0.021 0.17 0.23
Table 2 : A1, A2, A3 are the small angles which transform coordinates from this frame into ICRF; N is the number of the common defining ICRF sources used for the comparison; ra and rd are the weighted mean residuals in acos(d) and d respectively. Unit: 0.001".
Table 3 shows the systematic effects in this frame detected by their comparison to ICRF-Ext.1.
Da Dd Bd -0.001±0.001 +0.000±0.000 +0.002±0.017
Table 2: Da, Dd are the slopes in right ascension and in declination, respectively. Bd is the bias in declination. Units: 0.001"/degree for the slopes, 0.001" for the bias.
Remark : No deformations are detected in this frame when compared to ICRF.