Delivered-To: igsstation@igscb.jpl.nasa.gov Message-ID: <5ACEEE96F4F9D41190790002A528B51E07097753@S0-OTT-X11.NRCan.gc.ca> From: =?iso-8859-1?Q?=22Ferland=2C_R=E9mi=22?= To: "'igsstation@igscb.jpl.nasa.gov'" Subject: [IGSSTATION-330]: IGb00 Review - EISL - GOUG - IISC - MAC1 - MANA - NTUS - YAKT Date: Mon, 17 Jan 2005 11:05:02 -0500 Content-Type: text/plain; charset="iso-8859-1" Sender: owner-igsstation Precedence: bulk ****************************************************************************** IGS Station Mail 17 Jan 08:07:01 PST 2005 Message Number 330 ****************************************************************************** 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,