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SRRL PWV Instrument Descriptions and Histories

Model Measurement
Notes (below)
Units Install
(calc) Precipitable Water (PW) and PW error mm 06/13/2012 - - -
Precipitable Water amount and the associated error from the estimation process.
(calc) Zenith Wet Delay (ZWD) mm 06/13/2012 - - -
Estimated in GPS analysis software. Directly scalable to PW.
(calc) Zenith Hydrostatic Delay (ZHD) mm 06/13/2012 - - -
Computed from surface pressure measurements.
(calc) Zenith Total Delay (ZTD) mm 06/13/2012 - - -
Sum of ZWD and ZHD
(calc) K-factor unitless 06/13/2012 - - -
dimensionless scale factor between ZWD and PW
278 Surface pressure mBar 06/13/2012 - - -
Measured using SRRL BMS Setra analog pressure sensor by Campbell datalogger, which is collected by MIDC data acquisition every 3-seconds, then converted to an ASCII string which is sent via RS-232 to the Trimble Net9R as requested (every 60 seconds), see the SRRL BMS Instrument page for more information regarding the sensor. As of 4/27/2015, Campbell data logger now sends ASCII pressure string direct to Trimble via UDP.
  • Raw data is sampled by Trimble Net9R data acquisition every 30 or 60 seconds and send to UCAR every hour for data processing.
  • PWV processed data is grabbed by MIDC every hour (25 minutes from the top of the hour) from the UCAR web site and converted to "classic" Campbell data logger format so that it can be made available on the MIDC web site, which requires converting UTC to Mountain Standard Time (MST).
  • Data processing at UCAR takes 1 hour 35 minutes and resulting data sample rate is 30 minutes.