Content-class: urn:content-classes:message Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Tue, 22 Jul 2008 15:11:37 -0500 Message-ID: Thread-Index: AcjsNyWpOfjVCRH8QlS4sdHQtIqpMA== From: "Wiley, Barbara" To: Subject: [IGSMAIL-5796]: Message for igsmail Sender: owner-igsmail Precedence: bulk ****************************************************************************** IGS Electronic Mail 22 Jul 13:11:44 PDT 2008 Message Number 5796 ****************************************************************************** Author: Leonard Weingarth, NGA In close cooperation with CDDIS and the IGS Central Bureau, the National Geospatial-Intelligence Agency (NGA) is now supplying tracking data from 11 stations of its global network. The same stations are a major component of the operational GPS tracking network, which will allow a closer alignment of the WGS 84 and ITRF frames. At each of NGA's monitor stations, two collocated receivers run from a common antenna (an Ashtech Dorne-Margolin chokering) identified with a single DOMES number. The receivers in all cases are modified Ashtech Z-12 models. All NGA stations are equipped with environmentally controlled Agilent 5071A cesium clocks except for the station located at USNO, which references the USNO Master Clock Ensemble. Each receiver at each NGA site is connected to a separate cesium clock, except at USNO. NGA has supplied historic RINEX data to the IGS. However, NGA internal RINEX filenames do not map to a single, unique receiver as required by the IGS. In conjunction with this, it has been necessary to change site names to conform to IGS and RINEX standards. The details follow. 1. NGA internal site names and file formats NGA uses an internal data filenaming and format scheme that differs from the IGS standard. The internal RINEX observation and navigation filenames have the form: [r]xx[#]ddda.yyo & [r]xx[#]ddda.yyn where [r] has a value of s or u and refers to whether the file was collected by the [s]elected or [u]nselected receiver. NGA designates an active, or selected GPS receiver, and an unselected receiver. Either receiver/cesium 1 or receiver/cesium 2 can be the selected receiver/clock. NGA does not change receiver/cesium pairing except in the event of equipment failure. xx is the NGA internal station number, from 01 to 14 [#] is the receiver/cesium pair, either 1 or 2 ddd is the day-of-year, from 001 to 366 a is the session designator. For multiple sessions this value is incremented yy is the 2 digit year o or n refers to observation or navigation file, respectively. Meteorological data files are also collected at each site. 2. New IGS site names to be used To conform with IGS standards, NGA will modify its RINEX naming scheme in the following way to map the internal filenames to these new names: [r]021, [r]022 ade1, ade2 Adelaide, Australia [r]031, [r]032 bue1, bue2 Buenos Aires, Argentina [r]041, [r]042 hrm1, hrm2 Hermitage, UK [r]051, [r]052 bhr1, bhr2 * Bahrain (See Item 3.) [r]061, [r]062 qui1, qui2 Quito, Ecuador [r]071, [r]072 wdc1, wdc2 / wdc3, wdc4 * USNO, Washington, DC (See Item 4.) [r]101, [r]102 eil1, eil2 Eielson, Alaska, USA [r]111, [r]112 wel1, wel2 Wellington, New Zealand [r]121, [r]132 pre1, pre2 Pretoria, South Africa [r]131, [r]132 osn1, osn2 Osan, Korea [r]141, [r]142 tah1, tah2 Tahiti, Polynesia [s]/[u]-type filenames have been available at CDDIS for some time and some analysis groups have used those files. Please be aware that the old files will be replaced with the new names on 21 July 2008. After this date, all new data files from NGA will use the following names and conform to the RINEX 2.10 standards. Users of the old files should please discontinue that practice immediately. NGA will submit updated historic data in the near future. An announcement will be sent when that is accomplished. Note that all of the new NGA stations have S-type DOMES numbers, so the reference points are associated with the individual antennas and the eccentricities are zero. Only the previous IGS site bahr and its new name bhr1/bhr2 has a marker DOMES number and a non-zero eccentricity. 3. Station bahr to be replaced by bhr1 FOR July 21, 2008, NGA WILL STOP BAHR DATA SUPPLY and data file naming will change. In the past, the data supplied for bahr was the selected receiver. This resulted in a mixture of data from the different receivers. While the data primarily corresponded to receiver 1, whenever receiver 1 failed at Bahrain, receiver 2 data was supplied to CDDIS as bahr data. Using separate names (bhr1 and bhr2) for the receiver/cesium pairs at Bahrain should eliminate possible confusion in the future. 4. USNO antenna move: The NGA receiver antenna at USNO was moved on 2006-07-17. All data prior to this date will use the site names wcd1 and wdc2, depending on the receiver supplying the data. Data newer than 2006-07-17 will use the site names wdc3 or wdc4, respectively. The two locations for the antenna correspond to distinct DOMES numbers at USNO as indicated in the site logs. Note that these stations are not the same as the existing IGS stations, usno, usn1 (discontinued), or usn3. 5. Site logs New site logs have been prepared using the new site names given above and these will be deposited at the IGS Central Bureau.