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[IGSSTATION-330]: IGb00 Review - EISL - GOUG - IISC - MAC1 - MANA - NTUS - YAKT
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IGS Station Mail 17 Jan 08:07:01 PST 2005 Message Number 330
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Author: R. Ferland
Dear IGS colleagues,
It has already been almost one year since the IGb00
realization of ITRF is official. Due to the ongoing
evolution of the IGS network, this review of the current
realization is becoming necessary. A draft of this has
already circulated within the RFWG. The station DGAR was
also added to the original reviewed list from suggestions
by G. Gendt. The proposed changes to IGb00 will be
reflected at the central updating the SINEX files defining
the realization. The SINEX EPOCH block will be updated by
indicating up to when the stations are expected to be used
(EPOCHS block).
- Reference Frame stations previously removed:
FAIR - MAG0 - SFER - YSSK (Apr. 2004)
KOKB (Jun. 2004)
TRO1 (Aug. 2004)
- More Reference Frame stations to be removed:
EISL - GOUG - IISC - MAC1 - MANA - NTUS - YAKT (Jan. 2005)
These stations should be removed from the IGS realization
immediately.
Similarly to the previous reviews, average residuals
exceeding 7/15 mm in the horizontal/vertical components
as well as repeatedly rejected stations (exceeding 5 sigmas)
were checked. The stations statistics were estimated using
GPS weeks 1293 - 1302. Stations that were missing more than
50% of the time were also checked. Stations coordinates
affected by other known events were also included.
1)
========
Stations with large average horizontal/vertical residuals:
Station # N-E H
GOUG 10 3.1 24.0
MANA 8 11.9 8.5
YAKT 7 13.3 3.0
2)
========
Stations with repeated large normalized residuals:
ALGO IISC MANA YAKT
3)
========
Stations missing more than 50% of the time.
ASC1 EISL KSTU RBAY
4)
========
Other stations:
MAC1 NTUS DGAR
======================================================
======================================================
ALGO
Since GPS week 1300, the EW component
is off by about 7-11mm w.r.t. IGb00 & the cumulative
solution. This type of behaviour has occurred for a few
weeks every year at about the same time. It usually
returns to more normal residuals. So based on past
behaviour, it is expected to return to its normal self
soon.
I suggest to keep it.
ASC1
The station was providing reliable data and solutions
until recently.
I suggest to keep it.
DGAR
The station reported just reported by G. Gendt to have
also experienced potential effects that the recent large
earthquake in the region. From the IGS weekly solution
1303, the station may have moved by about 5mm in the
North and East directions, the elevation doesn't appear to
have been significantly affected. The recent solutions for
that station for previous weeks did not indicate anything
abnormal. The station was up to then, well behaved.
I suggest to keep it in for now, subject to the results
of upcoming solutions.
EISL
The station was scheduled to be terminated
at the beginning of 2005. (IGSMAIL-4899) Not processed
by any AC for about one year.
I suggest to remove it.
GOUG
The weekly station estimated vertical coordinate
have been off recently by ~20-30mm. The most recent
GPS week vertical residual however is somewhat puzzling
at 4.4mm. This week is believed to be an "anomaly"
but time will tell.
I suggest to remove it.
IISC
Since GPS week 1297 the station EW component
has been off by about 10mm w.r.t. IGb00 & the cumulative
solution. The time series indicates the residuals
have gradually "drifted" mainly in the EW direction
to that situation. The local people have indicated that
the cause may originate from weather had been unusually
wet. Equipment gradual performance degradation shouldn't
be ruled out. Starting with GPS week 1300, the station
was temporarily removed from the list of reference frame
stations, hoping for eventual improvement. This has not
been the case so far. In week 1303 combination just
released, the EW component also showed a jump of ~ 10mm.
It may have been caused by the large earthquake that the
region has experienced recently.
I suggest to remove it.
KSTU
The station was included by some AC until GPS
week 1289. No data from the station has been available
since.
I suggest to keep it.
MANA
Since mid-1290 the residuals show that some
apparent "drift" is occurring. There is no historical
information indicating that this may be a short term
repeating occurrence. The number of observations available
is also low. This may suggest either communication and/or
receiver problems.
I suggest to remove it.
MAC1
An earthquake (8.1) on Dec 23 appear to have
caused a discontinuity in the time series. Comparison
between the weekly (1303) solution and the cumulative
solution indicates a shift of (19,8,7)mm in the (N,E,H)
directions. The station was excluded from the reference
frame station list starting with GPS week 1303.
The station was otherwise performing well.
(also reported by J. Ray / K. Larson)
I suggest to remove it.
NTUS
The devastating earthquake (9.0) that occurred
on December 26 appear to also have had an effect on the
Reference Frame station located in Singapore. Comparison
between the weekly (1303) solution and the cumulative
solution indicates a shift of (-7,14,0)mm in the (N,E,H)
directions. The station was excluded from the reference
frame station list starting with GPS week 1303.
The station was otherwise performing well.
I suggest to remove it.
RBAY
The station was included by some AC until GPS
week 1268. No data from the station has been available
since.
I suggest to keep it.
YAKT
All components for this station have been gradually
degrading since about ~1298. Similar degradations have
occurred in the past (~ annually) and lasted a few weeks,
before resuming "normal" behaviour. It has temporarily been
removed from the SINEX products alignment since GPS week
1300. As of GPS week 1303, residuals wrt the cumulative
solution have reached ~30mm in both horizontal components.
I suggest to remove it.
======================================================
======================================================
For any of the stations where it is suggested to remove;
if the situation was to change, it/they could be reinserted.
Best Regards,
Remi,