GPS Update Information

The Scientific Facts Behind Solar Activity

Recently, there has been a lot of confusion and misinformation surrounding the effects solar activity has on GPS receiver accuracy. In order to understand the facts behind solar activity, we asked Dr. Mike Whitehead, Hemisphere GPS' Vice President of Technology, to literally clear the air of some common misconceptions.

Questions & Answers

Q:	Will the accuracy of single-frequency GPS receivers be reduced as a result of future solar activity?
A:	The accuracy of both single-frequency and dual-frequency receivers may be reduced on occasion just like they currently are today and were in the past. Reduced accuracy generally occurs for a limited amount of time (1-2 day periods) totaling approximately 18-36 days per year. This does not mean you will experience a loss of signal but simply a reduction in accuracy.
Q:	Will more costly dual-frequency receivers compensate for a reduction in accuracy caused by solar activity?
A:	Dual-frequency receivers will likely experience similar reduction in accuracy when compared to single-frequency receivers, although often to a lesser extent. Dual-frequency OmniSTAR HP users will likely experience less reduction in accuracy than OmniSTAR VBS users. Whereas, most dual-frequency SBAS receivers will perform the same as single- frequency SBAS receivers. Ultimately, the closer you are to your correction source, the better your performance will be.
Q:	How can growers ensure their systems operate accurately during solar activity disturbances?
A:	The most accurate system during solar activity disturbances is an RTK solution with a nearby base station. Outback Guidance offers both single-frequency (BaseLineX™) and dual-frequency (A220/A221) RTK solutions which will assist in achieving more reliable accuracy during solar flare activity.
Q:	Has the reliability of GPS changed as a result of solar activity?
A:	No, although users may occasionally experience a decrease in accuracy. Due to the 24+3 initiative, GPS as a holistic system actually improved in accuracy. Essentially, the GPS 24+3 initiative spread out the satellites in orbit, resulting in more effective constellation geometry and ultimately improved accuracy. (1)

Quick Facts

High solar activity during this solar cycle is expected to be less than when compared to the last solar cycle of 2001-02 (2)  ~ 90–95% of the time GPS will perform as normal Systems that use nearby reference stations will be less affected during days of high solar activity Even when absolute accuracy is affected, pass-to-pass accuracy may not be affected March 2006, NASA predicted the solar minimum would occur in 2011 or 2012 and be 30-50% stronger than the 2001-02 maximum.[3] May 2009, NASA changed their prediction suggesting the solar maximum will occur May 2013 and will be 30% weaker than in 2001-02.[2]   Related Articles & Links NASA - New Solar Cycle Prediction GPS World - 24+3 Configuration Space Weather References (1) GPS World - GPS 24+3 Configuration: A Closer Look (2010) (2) NASA – New Solar Cycle Prediction (2009) (3) NASA – Long Range Solar Forecast