IMPORTANT: Timing Errors Affecting RT130s

RefTek RT130 Timing Errors Affecting
PASSCAL and FA Experiments


Stations Affected: RT130 connected to a 130-GPS/01 with SiRF ublox Trimble module installed (aka SiRF-type)

Description of Problem: Starting on July 31, 2008 (julian day 213 2008), the SiRF-type started to shift in time by a second. Since then, the mysterious time shifts (back and forth) continue. At present, SiRF has no explanation for these time shifts.

Identifying SiRF GPS:

  • Visually: The SiRF has no ring around the base of the connector attachment. If you see a white or orange ring the unit is NOT a SiRF.
  • Log Messages: If your RT130 is using a SiRF GPS, the following message will be in your logfiles or the RefTek RT130 raw SOH file on the CF card:

(Garmin-type GPS clocks produce the string "EXTERNAL CLOCK TYPE: NMEA - Garmin")


Solution: None at this time. PASSCAL is working on a software solution to correct data collected with these clocks. Once we have a solution, PASSCAL will assist in correcting your data. We have also ordered Garmin replacements for all of our SiRF clocks. However, the Garmins are presently not in stock and it will be awhile before we can begin to replace SiRF units in the field.

Experiments with SiRF-type GPS Clocks

LOGPEEK Example Illustrating the Problem