Metrology Department

History of GPS Operations at SLAC

Oct 2001 Leica GPS System 530 purchased Three Leica SR-530 receivers plus accessories purchased. The purchase entails a demonstration and two training sessions.
Dec 2001 First trial field campaign  
Jan 2002 Bernese GPS Software Version 4.2 purchased Bernese GPS Software Version 4.2 purchased and installed on a Windows platform
  Pacific Crest radio modems (base and rover) upgraded to governmental frequency Pacific Crest radio modems (base and rover) of the 450-470 MHz frequency range replaced by same type modems with the governmental frequency range of 410-430 MHz. The transmitting and receiving frequencies are set to 416.425 MHz and stored in Channel 0 of the modems.
Feb 2002 Monument M40 becomes SLAC's master control station A Leica SR-530 receiver is installed permanently in a weatherproof box attached to the wooden deck, a Leica AT-504 choke ring antenna plus weather dome is mounted on top of the monument. The weatherproof box also houses the Pacific Crest base radio modem, a power outlet, and an Ethernet connection (data download, however, is done manually using the FlashCard of the SR-530).
Mar 2002 Antenna mount changed The new mount is about 20 cm lower than the initial setup.
  Weather dome removed Phase center variation tables for the AT-504 are only available in versions without radome.
Apr 2002 RTK Mapping begins  
Jun 2002 RTK Mapping presentation  
Jun 2002 Bernese Processing Engine (BPE) set up for daily GPS solutions under Windows Daily solutions for a regional network are computed using the Bernese Processing Engine (BPE) under Windows. Processing performed when new observation data are downloaded from the FlashCard of the SR-530.
  Precise coordinates determined for M40 at reference epoch 2002.36. Precise coordinates determined for M40 at the reference epoch 2002.36
Jan 2003 Leica RS-500 receiver purchased Following some tests, the RS-500 replaces the SR-530 in the weatherproof box (the SR-530 can now be used as a rover unit). The GPS observations are continuously logged. The RS-500 is controlled by Leica's ControlStation software from a PC in the office. The necessity to connect the RS-500 directly to the logging PC via RS-232 cable is removed by employing an RS-232 Ethernet converter.
Feb 2003 GPS-RTK operations verified using the RS-500 RTK correction signal is transmitted via the Pacific Crest radio in the Leica format.
Mar 2003 Second weatherproof box installed at M40 A second weatherproof box is installed at M40 to accommodate an uninterruptible power supply (UPS). The RS-232 Ethernet converter is moved to the new box as well.
Apr 2003 Bernese GPS Software Version 4.2 under Linux Bernese installed on Linux platform. The Windows/DOS version is known to show instabilities in the BPE. This problem was repeatedly observed doing the daily processing of SLAC M40.
  ControlStation Monitor Program "monitor" installed "monitor" is an in-house product coded in Visual Basic that monitors Leica's ControlStation software for possible run-time errors (notifying the operator by email in such a case) and performs a quality check and a reformatting of the RINEX files.
Jun 2003 Anonymous FTP space set up AFTP space at SLAC's computing center set up for storing RINEX observation files. The storage capacity amounts to 500 MB.
  Bernese Processing Engine (BPE) set up for daily solutions under Linux, automatization enabled The data analysis runs in a fully automated mode using the Linux scheduler for its daily run at 4 a.m. local time.
Jul 2003 Back-processing of daily GPS solutions All GPS data available to the current date are reprocessed under Linux.
  Precise coordinates and velocities for M40 for the epoch 2002.90 determined New coordinate and velocity values determined for SLAC M40 using all available data. The reference epoch 2002.90 is in the middle of the used data window.
Oct 2003 Logging PC replaced The old logging PC could not be upgraded to Windows XP due to limited resources. All pertinent software is ported to new Windows XP PC.
Nov 2003 Disclaimer notice and DOMES number obtained Disclaimer notice put into AFTP space. DOMES number obtained for SLAC M40 changing the official name to SLAC 49523S001. All RINEX observation files have been edited to reflect the name change as well as to contain a reference to the disclaimer notice.
Dec 2003 Output RTK data in CMR format Made CMR format data available on network from second channel of RS-500 using serial to TCP/IP converter box.
Feb 2004 Internal report on SLAC's permanent GPS station An internal report has been compiled describing the data handling of SLAC's continuously operating GPS station.
Mar 2004 RTK correction signal format changed to RTCM V2.2 RTCM Version 2.2 (msg types 1 & 2 & 3 & 18 & 19 & 22) used instead of Leica format. With RTCM V2.2 the transmitted reference station coordinates have sub mm accuracy. Leica/CMR are good to 1 mm, RTCM V2.1 only has cm level.

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Last update: March 08, 2007