On the Edge: Five Big Ones in Ten

January 1, 2011  - By
Image: GPS World


Look back with me at the five 2010 GNSS events that most affected surveying, mapping, engineering, construction, and natural resource users. Each one had, or could have had, a significant effect on you and your work. Taking it from the top:

GPS 24+3 Constellation. The most important event occurred a year ago, when the Air Force began implementing a new GPS 24+3 configuration. They had their military reasons, but the benefit for you and me is eliminating GPS brownouts — periods with fewer GPS satellites in view. When combined with obstructions such as terrain, trees, or buildings, they made GPS hard to use.

It’s especially an issue with real-time kinematic (RTK) high-precision users because RTK technology is satellite-hungry. It needs six or more satellites to provide a robust position solution.

The Air Force moved three satellites, SVNs 24, 26 and 30, from their original slots. SVNs 26 and 30 have already reached their destinations, and SVN 24 will do so this month.

Three other satellites are being shifted slightly. SVN 55 found its new slot in December, while SVNs 46 and 56 start this month and should have completed their journeys by May/June 2011.

By now, you should be seeing some improvements in GPS satellite visibility. 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 those in obstructed environments such as tree canopy.

First GPS Block IIF. 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 marks the beginning of a new era in high-precision GPS positioning. The Block IIF launch was the catalyst for my June column “What Happen When High Accuracy is Cheap?”

This IIF is just a teaser though, and its fellows will launch at a snail’s pace. Remember though, it costs upwards of $200 million to launch a satellite and since there ares already 30+ operational GPS satellites in orbit, it’s hard for Congress and the Air Force to justify speeding up the launch schedule. The last target I heard was to have 24 satellites broadcasting L5 by 2019.

GLONASS Growth. Despite the recent catastrophe, the Russian Federation was still able to launch seven new satellites in 2010, including a new K1 satellite that will test a new CDMA signal for better compatibility with GPS.With 21 operational satellites and three more coming in March, a consistent and healthy number of GLONASS satellites in orbit has given receiver manufacturers more confidence to develop GPS/GLONASS receivers. This year, we’ve seen several manufacturers integrating GPS/GLONASS into handheld receivers as well as OEM board products.

User benefits are clear: more robust positioning and improved productivity due to decreased down-time.

Solar Activity. The big news is no news: the sun was eerily quiet in 2010. If your GPS receiver didn’t work at times this year, it wasn’t due to solar activity. But it may ramp up in 2011.

GAGAN, WAAS Failures. The Indian Space Research Organisation and the U.S. Federal Aviation Administration received a hard lesson in SBAS GEO management. In April, an Indian rocket launch failed, and one of the FAA WAAS satellites lost communication with its ground control.

If you’re an SBAS user, don’t let it bring you down. SBAS is here to stay, and likely you were not affected by either incident — unless you work in northwest Alaska. A new U.S. SBAS satellite came online, and India is regrouping for more launches.

Follow Eric on Twitter at GISGPS_Eric.

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