Temporary GPS outages in 2010 and beyond

INCREASING solar flare activity and a lagging satellite replacement program could see some temporary GPS outages in 2010 and beyond, with potential impacts on the agriculture and mining sectors.
For GPS-dependent graingrowers, GPS expert Rob Lorimer’s advice is to be “alert, but not alarmed” about these factors throwing autosteer tractors and other GPS-dependent machinery out of line.

The Position One consultancy managing director said the likelihood of either issue causing a serious GPS malfunction was very small, “in the order of 1-2 per cent” but the possibility was there.

He explained that GPS accuracy has been steadily enhanced over the past few years because the 11-year solar flare cycle had subsided into a quiet phase, resulting in less disturbance to the ionosphere and less interference for GPS units communicating with satellites.

“The United States military prescribes a quality of service for the GPS to operate within,” he said.

“In the past few years the accuracy has been well inside the prescribed quality, by an order of magnitude.”

But starting in 2010, a renewed bout of flare activity is due to start, bombarding Earth with high-energy solar winds that can agitate the ionosphere “the upper atmosphere” and send GPS communications astray.

GPS units typically triangulate a position from at least five to six satellites. If some of those satellites are low on the horizon, Mr Lorimer said, the angle means that the signal has more atmosphere to work through and there is more scope for interference.

Source: http://sj.farmonline.com.au/news/state/grains-and-cropping/general/outrage-alert-for-gps-growers-as-satellites-age/1625191.aspx