With this being my last column in 2010, I’m going to look back at the five significant GPS/GNSS events in 2010 that affected the surveying, mapping, engineering, construction, and natural resource users. Each of these had, or could’ve had, a significant effect on your GPS activities.
These are listed in order of importance with #1 being the most important.
1. GPS 24+3 constellation. The most important GPS/GNSS event in 2010 occurred back in January, when the Air Force announced it was implementing a new GPS 24+3 configuration. You can read about it in in more detail here, but the idea behind it was to eliminate GPS “brownouts.” These are periods in which there are fewer GPS satellites in view, and when combined with obstructions such as rugged terrain or trees or buildings, make GPS difficult to use.
It’s especially an issue with real-time, high precision users (RTK) because RTK technology is satellite-hungry. It needs six or more satellites to provide a robust position solution.
If you recall, in the new 24+3 configuration, there were three satellites moving significantly from their original slots (SVNs 24, 26 and 30). SVN 26 is already at its destination. SVN 26 is scheduled to reach it destination in January 2011. SVN 30 should have arrived at its destination in the past few days.
In addition, three other satellites (SVNs 46, 55, and 56) are being shifted slightly. SVN 55 should arrive at its destination this month. SVNs 46 and 56 are scheduled to begin transitioning in January 2011 and should be complete in May/June 2011.
By now, you should be seeing some improvements in GPS satellite visibility as the 24+3 configuration is almost complete. From the scenarios I plotted in this article, you can see that although you’ll see fewer peaks (high number of GPS satellites in view), you’ll also see fewer valleys (low number of GPS satellites in view). This should increase productivity for RTK users and users in environments where satellites signals are obstructed (such as under tree canopy).
2. Launch of the first GPS Block IIF satellite. Although it doesn’t really help users at this point other than being another satellite to enter service, the Block IIF satellite launched in May is the first to broadcast the third civil signal, L5. The L5 civil signals marks the beginning of a new era in high-precision GPS positioning. The Block IIF launch was the catalyst for the article I wrote I entitled “What’s Going to Happen When High-Accuracy GPS is Cheap?”
It’s just a teaser though, the launch of the next Block IIF isn’t until next summer at the earliest. Then, the next one is ???. They are being launched at a snail’s pace. Remember though, it costs upwards of $200 million to launch a satellite and since there’s already 30+ operational GPS satellites in orbit, it’s hard for the U.S. Congress and the U.S. Air Force to justify speeding up the launch schedule. During the last Air Force briefing I attended, the target was to have 24 satellites broadcasting L5 by 2019.
Block IIF GPS satellite (Courtesy: The Boeing Co.)
3. Continued development of GLONASS. Despite the recent launch failure (three GLONASS satellites crashed into the Pacific Ocean), the Russian Federation was still able to launch six new GLONASS satellites into orbit in 2010, and with another launch scheduled for later this month of the new GLONASS-K1 satellite, that will test the new CDMA capability for better compatibility with GPS.
As it stands, there are 20 operational GLONASS satellites in orbit, with four more offline for maintenance and two reserved as spares. That’s 26 total. Furthermore, after the Dec. 5 launch failure, Russian Federal Space Agency Director Anatoly Perminov vowed to return the GLONASS constellation to 24 operational satellites by March 2011, something that hasn’t been accomplished since the mid-1990s (albeit briefly).
A consistent and healthy number of GLONASS satellites in orbit has given receiver manufacturers more confidence to develop GPS/GLONASS receivers. Just this year, we’ve seen new receivers from several manufacturers that have taken GPS/GLONASS a step further in integrating them into handheld receivers as well as OEM board products.
For users, the benefits are clear, with the new 24+3 GPS configuration and a healthy number of GLONASS satellites in orbit, GPS/GLONASS users are seeing the most satellites in view ever in the history of GPS/GLONASS. Signals from more satellites typically results in more robust positioning and improved productivity due to decreased down-time.
Rocket launch containing three GLONASS satellites
4. Solar activity affect on GPS. Solar activity was eerily quiet in 2010. The big news is that there was no news. There were some minor solar events in 2010, but despite what you may have read, none of them were strong enough or the type that would affect GPS operations.
So, if your GPS receiver didn’t work at times this year, it wasn’t due to solar activity.
With the peak of the current Solar Cycle (SC 24) estimated to occur in May 2013, solar activity should be ramping up in 2011. In August, I conducted a webinar that discussed, among other things, the subject of solar activity on GPS. You can read a summary of it here and even download the webinar presentation.
You can be sure I’m closely monitoring solar activity for any events that look like they will have an effect on your GPS operations. I’m still working on my notification system and will keep you updated on that. Otherwise, the GPS World website is a good source for news in this area.
Finally, I’ll be attending the Space Weather workshop in April 2011. Most, if not all, of the really smart space weather people from around the world gather and confer on space weather. I’ll be writing about what I hear and learn from these folks. But, the sun is a mysterious creature. I like to get definitive answers to my questions, but even some of the brightest scientists I know will answer with “I really don’t know” when I ask them about a certain behavior of the sun. Mother Nature is humbling at times.
Solar Cycle 24 Prediction (Courtesy: NOAA Space Weather Prediction Center)
5. The GEO failures of GAGAN and WAAS. Both the Indian Space Research Organisation (ISRO) and the U.S. Federal Aviation Administration (FAA) were delivered a hard lesson in SBAS GEO satellite management. The SBAS GEO satellites are the ones that broadcast the integrity and correction information to users. They are the critical communications link that connects the SBAS ground infrastructure to the end users. Without them, SBAS doesn’t work.
In April, the ISRO rocket launch of their GAGAN GEO satellite failed, sending the critical GAGAN GEO satellite splashing into the Bay of Bengal. GAGAN is still in testing phase, so no users were affected, but it set back the GAGAN program. However, it didn’t delay GAGAN as much as I thought it might. Another GAGAN GEO is set to launch later this month (as of December 29, the launch date has now been pushed out to Q1 2011) with a second due to launch in the first part of 2012. The ISRO completed its Preliminary System Acceptance of GAGAN just a few days ago. The aviation-certified system is expected to be operational by June 2013. As with other SBAS, test signals usable by non-aviation users will likely be available during the testing phase, as early as 2011.
Also in April 2010, it was reported that the contractor operating one of the FAA WAAS GEO satellites lost communication with the satellite (PRN 135). It was reportedly an unprecedented event. Initially, it was thought that PRN 135 would drift out of usable orbit within a few weeks, leaving North America with only a single WAAS GEO until a new one was brought into service (PRN 133 was already under testing). Things weren’t quite as bad as they seemed as PRN 135 ended up staying in a usable orbit up until PRN 133 testing was concluded.
However, the defunct PRN 135 was at 133° west longitude and PRN 133 is at 98° west longitude. With the remaining GEO (PRN 138) at 107° west longitude, users in northwest Alaska do not have WAAS service. Since none of the GEO satellites are actually owned by the FAA, they have little say in the location of the GEO satellite. The FAA says they are working on putting two more GEOs into service, but that takes time, and it’s not measured in months, but rather years.
I think the hard lesson is not to skimp on SBAS GEO satellites. Perhaps this event will make it easier for the FAA to sell the concept to Congress (for funding).
If you’re an SBAS user, don’t let this bring you down. SBAS is here to stay, and likely you were not affected by any of the above. These past few days, I’ve been looking at SBAS data (and DGPS data) collected over a 24-hour period. The accuracy and stability is pretty impressive.
That leads me into my last subject which is a webinar I’m conducting on January 26, 2011.
It’s entitled: SBAS, DGPS or Post-processing? Which Should You Use?
If you are using or plan on using GPS for mapping or surveying, you should seriously consider attending this webinar.
Learn the real story behind each of these technologies without a marketing or salesperson’s bias.
Tens of thousands of users around the world utilize GPS/GNSS receivers for mapping, surveying and navigating. Since autonomous GPS/GNSS typically does not provide the needed accuracy, users must rely on a source of GPS/GNSS corrections. There are three sources of GPS/GNSS corrections available to users who desire reliable GPS/GNSS accuracy in the sub-meter to three meter range: SBAS, DGPS and post-processing. Dr. Michael Whitehead, VP of Technology at Hemisphere GPS, will join me in presenting a background on the three technologies as well as the strengths and weaknesses of each.
I’ve known Mike for a number of years. He was an early innovator in the development of SBAS technology at Satloc as well as SBAS and DGPS receiver technology at Hemisphere GPS. He is one of the leading GNSS engineers in the world. I’m particularly excited about this event and promise a lively discussion that’s full of useful information, data, and concepts that anyone using or considering using GPS/GNSS for mapping, surveying, or navigating will find useful.
Have a safe and happy holiday and a Happy New Year. See you next year.
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