Technical description of dgfd0002.snx
-------------------------------------
1. Purpose: Datum free VLBI session normal equation files in SINEX 2.0
format, including epoch coordinates and EOP.
2. Analysis Center: Deutsches Geodaetisches Forschungsinstitut (DGFI),
Munich, Germany
3. Short description:
More than 2600 VLBI session SINEX files starting on january 4th, 1984
are generated. All in all, this set of files contains VLBI data of 49
telescopes. These sessions were selected considering the following
criteria (with a few exceptions):
- 24 h or longer sessions only
- at least three telescopes participating (each with more than 100 obs)
- at least 250 observations per session
- only non-mobile telescopes
- only telescopes with sufficient data allowing to determine reliable
velocities
The following stations are assumed to have discontinuities (jumps)
in their position time series:
NRAO85 3 901201
MOJAVE12 920627
DSS15 920627 (only data after 920627 included in this series)
MEDICINA 960601
EFLSBERG 961001
DSS65 970415
TSUKUB32 990401
GILCREEK 021103
4. Estimated parameters:
a. Celestial frame: No
b. Terrestrial frame: Yes
c. Earth orientation: Pole coordinates and their first derivatives,
UT1-UTC and LOD, dpsi, deps, each valid for the duration of the
session (normally 24 h), reference epoch is mid of session
d. Zenith troposphere (per station): one offset for the whole session
plus a piece-wise-linear function with rates valid for one hour,
each of the rates constrained to 0 with 10 mm/sqrt(h)
e. Troposphere gradient: one offset per station for the whole session,
constrained to 0 with 0.5 mm
f. Station clocks: Quadratic function plus a piece-wise-linear function
with rates valid for one hour, each of the rates constrained to
0 with 30 mm/sqrt(h) (occasionally are clock jumps estimated
additionally)
g. Baseline clocks: None
h. Other: None
5. Celestial reference frame:
a. A priori source positions: solution DGFI05R01, which was computed
with the 199 stable sources (according to Feissel-Vernier, A&A,
2003) constrained to have NNR w.r.t. ICRF-Ext1
b. Source positions adjusted in solution: No
6 Terrestrial reference frame:
a. A priori station positions: solution DGFI05R01, which was computed
with coordinates and velocities of 25 long term stable and globally
distributed stations constrained to have NNR and NNT w.r.t. ITRF2000
b. A priori station velocities: solution DGFI05R01, which was computed
with coordinates and velocities of 25 long term stable and globally
distributed stations constrained to have NNR and NNT w.r.t. ITRF2000
c. Axis offsets: taken from official IVS-table
http://giub.geod.uni-bonn.de/vlbi/IVS-AC/data/axis-offsets.html,
except the value 0.0 for KWAJAL26 which is not in that list and thus
from blokq. It is supected to have its origin from the telecope's
construction plans.
d. Reference epoch: session epoch
e. Relativity scale: IERS Conventions 1992 ("consensus model")
7. Earth orientation:
a. A priori precession model: IERS 1996
b. A priori nutation model: IERS 1996 (no FCN corrections applied)
c. A priori x and y pole coordinates and rates, dUT1 and LOD: IERS
EOP-C04, linearly interpolated (before the interpolation of dUT1,
UT1R variations according to IERS Conventions 2003 are substracted
from the daily UTC 0h C04 values. After the linear interpolation,
the UT1R corrections are added again).
d. A priori short period (~daily and subdaily) tidal variations in
x, y, dUT1: IERS Conventions 2003
e. EOP estimation: Pole coordinates and rates, UT1-UTC and LOD,
dpsi, deps, each valid for the duration of the session
(normally 24 h), reference epoch is mid of session (see the
SOLUTION/APRIORI block)
8. A priori geophysical models:
a. Troposphere: hydrostatic component from surface pressure (in
general as reported in the NGS files) mapped with the Niell 1996
dry mapping function, wet delay is estimated with the Niell 1996
wet mapping function. All A priori values for the gradients are
zero.
b. Solid Earth tide: IERS Conventions 2003 (no non-correction of the
permanent tide; comment: this is not conform with the IAG
resolution but common practice)
c. Ocean loading: IERS Conventions 2003, per station 11 partial tides
provided by H.G. Scherneck
d. Pole Tide: IERS Conventions 2003, using the linear approximation
of the mean pole path
e. Atmosphere loading: -
f. Thermal deformation: -
9. Data type: Group delays
10. Data editing: 5-degree elevation cutoff
11. Data weighting: Only observations with a zero quality flag in NGS
cards are used. The weights determined during the correlation process
(read from the NGS files) are refined by station and elevation
dependent fractions. All observations are subject to an outlier test
(data snooping).
12. Software: DOGS_CS and OCCAM 6.1e, least squares method (LSM)
13. Further information:
The SINEX 2.0 files include datum free normal equations only, no
solution. None of the station postion parameters or EOP reported in
this file are subject to any constraints.