OBJECTIVE
|
Before proceeding with the full reprocessing campaign, a 3-month test
period at the beginning of year 2000 was chosen to evaluate the analysis
procedures and performances of the Analysis Centers (ACs), as well as
exercise the reprocessing combinations.
|
TEST
SINEX
FRAME
RESULTS
|
The ACs provided
test solutions for the first quarter of year 2000 (GPS weeks 1042-1059;
the ESA solutions cover the 14 weeks from 1042-1055).
Statistics for the station position residuals (average weighted mean &
average standard deviation) from the combination of the weekly SINEX
files from each AC, after removing separate Helmert transformations
(see following), are tabulated below.
| SINEX Terrestrial Frame Residuals
|
AC
code
|
#
wks
|
#
sta
|
w.r.t. Weekly Combination
|
w.r.t. Cumulative Combination
|
| N
|
E
|
U
|
N
|
E
|
U
|
| (mm)
|
(mm)
|
(mm)
|
(mm)
|
(mm)
|
(mm)
|
ESA (old)
±
|
14
|
107.3
|
0.7
3.3
|
0.2
5.0
|
-2.2
9.5
|
1.0
3.5
|
0.4
5.2
|
-2.2
10.3
|
ESA (new)
±
|
14
|
120.5
|
0.6
2.3
|
0.1
3.7
|
-1.0
7.2
|
1.1
2.6
|
0.1
3.9
|
-0.9
8.3
|
MIT
±
|
18
|
261.3
|
-0.4
1.6
|
-0.1
1.9
|
0.3
5.0
|
0.1
4.5
|
0.1
1.9
|
0.4
5.9
|
NGS (old)
±
|
13
|
168.9
|
0.3
3.9
|
0.6
4.8
|
0.6
7.7
|
0.7
4.2
|
0.8
5.1
|
0.7
8.3
|
NGS (new)
±
|
18
|
170.1
|
-0.4
2.4
|
0.3
2.6
|
-0.7
5.2
|
-0.1
2.7
|
0.4
3.1
|
-0.7
6.3
|
PDR
±
|
18
|
151.5
|
0.0
2.0
|
0.2
2.0
|
-0.5
5.2
|
0.4
2.2
|
0.2
2.2
|
-0.4
6.2
|
SIO
±
|
18
|
212.9
|
-0.8
1.5
|
-0.3
2.8
|
-0.5
4.1
|
-0.5
1.8
|
-0.2
3.2
|
-0.5
5.2
|
The mean & standard deviation of the Helmert parameters
for the weekly SINEX file alignments to IGS05 are tabulated below
for each AC during this test period (GPS weeks 1042-1059).
| SINEX Frame Helmert Parameters w.r.t. IGS05
|
AC
code
|
#
wks
|
RX
|
RY
|
RZ
|
TX
|
TY
|
TZ
|
Scl
|
| (µas)
|
(µas)
|
(µas)
|
(mm)
|
(mm)
|
(mm)
|
(ppb)
|
ESA (old)
±
|
14
|
81.8
40.1
|
-0.6
59.3
|
-208.6
497.6
|
-1.2
5.0
|
1.7
9.8
|
-57.7
53.0
|
0.47
0.22
|
ESA (new)
±
|
14
|
54.4
38.0
|
-70.6
54.1
|
293.1
144.8
|
-1.2
3.7
|
-0.7
3.8
|
6.2
6.4
|
0.02
0.17
|
MIT
±
|
18
|
-19.8
9.0
|
-11.1
12.1
|
2.3
13.2
|
-7.5
2.6
|
6.9
5.9
|
20.2
7.9
|
-0.30
0.11
|
NGS (old)
±
|
13
|
5.9
37.1
|
7.9
67.8
|
-41.9
35.2
|
-0.6
4.5
|
2.0
3.3
|
0.3
5.3
|
-1.79
0.25
|
NGS (new)
±
|
18
|
26.6
46.1
|
-49.7
65.2
|
-4.6
19.6
|
-0.3
4.2
|
2.8
4.5
|
-11.3
6.7
|
-0.96
0.15
|
PDR
±
|
18
|
13.1
9.0
|
-38.2
10.6
|
16.4
6.4
|
-4.0
2.9
|
7.5
6.5
|
-0.5
17.3
|
-0.81
0.10
|
SIO
±
|
18
|
28.4
197.5
|
75.4
82.0
|
-41.7
62.1
|
-8.2
2.8
|
5.1
8.0
|
10.1
18.8
|
-0.03
0.16
|
There are 319 stations in the test cumulative solution file (SINEX format),
which is available in file
IG000P17.ssc.Z
(unix compressed) or uncompressed as
IG000P17.ssc.
In addition, Remi Ferland has produced the following postscript (ps) plots
concerning the test SINEX combinations:
Table 5-1 —
number of stations & variance factors for each AC
Table 5-2-1 —
station residual statistics w.r.t. IGS05
Table 5-2-2 —
station residual statistics w.r.t. weekly combination
Table 5-2-3 —
station residual statistics w.r.t. cumulative combination
Table 5-3-1 —
Helmert transformation parameter estimates to IGS05
Table 5-3-2 —
Helmert transformation parameter standard deviations to IGS05
Table 5-4 —
combined apparent geocenter offsets & standard deviations
|
TEST
SINEX
ERP
RESULTS
|
Earth rotation parameter statistics (mean & standard deviation) for each AC
during the test period (GPS weeks 1042-1059) are tabulated below. The PDR
ERPs have been rejected due to the use of continuity over-constraints;
see this site
for further information. The SIO ERPs have the same problem but have
not be excluded here; this explains their unrealistically small rate
variations.
| ERP (SINEX) Combination Comparisons
|
AC
code
|
#
wks
|
X pole
|
Y pole
|
X pole rate
|
Y pole rate
|
LOD
|
| (µas)
|
(µas)
|
(µas/day)
|
(µas/day)
|
(µs)
|
| included solutions:
|
ESA (old)
±
|
0
|
---
---
|
---
---
|
---
---
|
---
---
|
---
---
|
ESA (new)
±
|
0
|
---
---
|
---
---
|
---
---
|
---
---
|
---
---
|
MIT
±
|
18
|
-16.1
32.1
|
41.4
64.7
|
-194.9
186.5
|
-258.4
257.1
|
-26.4
23.7
|
NGS (old)
±
|
13
|
144.3
129.9
|
285.4
108.8
|
-60.0
176.2
|
-112.1
272.2
|
103.8
46.1
|
NGS (new)
±
|
18
|
-23.6
68.2
|
9.3
42.4
|
-55.6
80.6
|
-28.4
166.1
|
53.4
56.0
|
PDR
±
|
0
|
--
--
|
--
--
|
--
--
|
--
--
|
--
--
|
SIO
±
|
18
|
37.0
65.6
|
-51.2
54.6
|
4.1
12.7
|
3.2
11.1
|
14.6
18.0
|
| for comparison only (IERS Rapid Service Bulletin A):
|
Bull A
±
|
18
|
-66.7
40.2
|
16.4
51.9
|
-0.1
15.3
|
-3.1
16.7
|
-8.4
22.1
|
In addition, Remi Ferland has produced the following postscript (ps) plots
concerning the test SINEX ERP combinations:
|
TEST
ORBIT
RESULTS
|
Orbit combination statistics (mean & standard deviation) for each AC
during this test period (GPS weeks 1042-1055) are tabulated below.
| Orbit Combination Comparisons
|
AC
code
|
#
wks
|
DX
|
DY
|
DZ
|
RX
|
RY
|
RZ
|
Scl
|
RMS
|
WRMS
|
| (mm)
|
(mm)
|
(mm)
|
(µas)
|
(µas)
|
(µas)
|
(ppb)
|
(mm)
|
(mm)
|
| included solutions:
|
ESA (old)
±
|
13
|
0.2
1.3
|
0.8
3.0
|
-2.3
3.9
|
10.5
102.8
|
92.9
58.5
|
34.4
97.8
|
-0.55
0.15
|
64.4
8.3
|
64.4
8.3
|
MIT
±
|
13
|
-1.2
1.2
|
-0.8
1.1
|
2.9
5.1
|
61.5
81.0
|
22.1
48.8
|
8.1
33.0
|
-0.01
0.18
|
25.2
6.8
|
19.6
1.8
|
NGS (old)
±
|
12
|
0.4
1.0
|
1.8
2.1
|
-12.2
3.5
|
28.6
47.0
|
-29.1
97.1
|
-46.3
52.9
|
1.35
0.12
|
30.6
1.9
|
28.1
1.9
|
PDR
±
|
13
|
-0.5
0.5
|
1.1
1.8
|
0.6
11.2
|
7.5
70.0
|
89.2
49.6
|
71.3
29.8
|
-0.81
0.17
|
27.5
1.4
|
25.5
1.1
|
SIO
±
|
13
|
2.2
1.1
|
-3.4
1.8
|
9.4
5.9
|
-178.8
322.5
|
-180.5
147.5
|
-78.2
58.7
|
-0.13
0.10
|
40.6
9.4
|
34.6
7.4
|
| for comparison only (original IGS Final solutions):
|
IGF
±
|
13
|
-1.7
1.7
|
0.7
1.7
|
8.3
5.0
|
1.8
72.0
|
18.4
50.8
|
125.5
54.7
|
-0.65
0.14
|
27.7
1.4
|
24.2
1.5
|
|
ISSUES
TO BE
RESOLVED
|
Based on the test results, there are several outstanding issues
and questions that should be resolved:
all ACs need to update their analysis summaries
- including operational & reprocessing ACs
- CODE last updated 12 Mar. 2002
- EMR last updated 23 Jan. 2002
- GFZ last updated 27 Feb. 2003
- JPL last updated 13 Apr. 2004
- MIT last updated 28 Jan. 2004
- SIO last updated 31 Oct. 2005
new ESA & NGS solutions generally much improved
over original solutions
not all metadata used by ACs is consistent
with the epoch of the observational data
- MIT SINEX comparisons to the IGS
cumulative solution indicate an inconsistency in the N
component metadata
RMS global consistency of AC SINEX frames not
quite as good as in routine operational solutions
differences in alignment of AC SINEX frames
sometimes exceed 2 cm in their weekly TZ geocenter offsets
- the ESA solutions dominate the
combined geocenter value due to very small formal errors
differences among AC polar motion rate solutions
sometimes exceed 200 µas/d
- NGS LODs are significantly offset
& have poor stability
differences among AC orbit solutions
sometimes exceed 1 cm in their DZ origin components
- NGS orbit DZ origin offset most
differences among AC orbit solutions
sometimes exceed 100 µas in their rotational orientation
- SIO orbit rotations largest & most unstable
the relative agreement among the participating
ACs is generally fairly good, but it is not at the level of the
current IGS operational Final products
constraints on the Earth rotation rate
parameters are not handled consistently among ACs
- affects the PDR & SIO
polar motion rates
only two ACs provide usable clock
estimates
- not sufficient for a robust combined
clock product
verify that all necessary IGS metadata files
are current & complete
- include metadata for all historic &
discontinued stations in the IGS master SINEX template file,
igs.snx
- master file of P1-C1 satellite code biases back to 1994
organize product archiving & file naming
structures
|
STEPS
AHEAD
|
The following schedule is suggested:
Feb. 2008 — begin full
reprocessing phase
- start with data for week 1459 (23-29 Dec 2007)
- then work backwards in time, hopefully back to 1994.0
02-06 June 2008 — IGS workshop
- evaluate progress for initial phase of reprocessing
|
