• The Wide Area Augmentation System (WAAS-Real-Time) Intelsat CRW geostationary (GEO) satellite “PRN 135” has ceased broadcasting the WAAS signal as of December 16, 2010. The deterioration of the satellite’s ability to remain stable over the past few days caused intermittent data link disruptions that rendered the satellite unreliable for further data transmissions.  For more information click on this article link: SBAS/WAAS PRN 135 Satellite Ceases Broadcast.  This loss of PRN 135 will affect the North Western part of North America.
  • In the past 3 years we have been able to receive a live correction from either PRN 135 or PRN 138 on our Mapping Grade GPS units.  If you could not receive one of them then your receiver (if set to track both under real-time settings) would try to obtain a correction from the other.  If neither of these SBAS/WAAS satellites were available to provide you a 1-5 meter horizontal solution then you were left with an Autonomous GPS signal (10-15 meters in horizontal accuracy).   Your next step would be to Post Process your GPS to achieve required accuracies.  Your alternative for Real-time correction or for navigation is to then use a local VRS/RTN correction (not availabe in all states).  In a future Post I will go into more detail of the availability of VRS/RTN corrections in the Midwestern USA.
  • I will post any updates I find out about PRN 133 that is taking the place of PRN 135.  A GPS Firmware release for Trimble MGIS products would be needed in order to track and lock onto PRN 133.  Stay Tuned.