GPS monitoring – The modern GPS monitoring receiver has a typical accuracy of an astonishing twenty feet, reducing the venerable ‘Art and Science of Navigation’ to little more than a simple read-out of the latitude and longitude, which can then be automatically displayed on an electronic chart or map.
But is it possible that the GPS monitoring signal might become unavailable for a time, or worse still, might the position obtain be inaccurate and misleading? To answer those questions it’s helpful to know a little about how GPS monitoring works, and then to see what might cause such problems.
The user’s position is calculated by measuring distances from a group of three or four satellites (four if airborne) in space so as to obtain intersecting position circles by a process known as ‘trilateration’. How is this distance measured?
The GPS monitoring signal travels down to earth from the satellite at the speed of light (186,000) miles per second and using the basic equation, Velocity x Time = Distance, the GPS receiver unit calculates the range from the satellite by measuring precisely the time taken for the signal to reach it from the satellite.
It’s worth remembering that if the signal from the satellite is delayed by even one-thousandth of a second, the distance will be out by a hundred and eighty-six miles!
Reasons for Errors in GPS Monitoring Data
Provided there is no satellite or GPS monitoring receiver equipment errors and no reflection occurs, the GPS monitoring signal emitted from a navigation satellite orbiting in space may be delayed on its route to earth as it passes through:
The ionosphere – a blanket of charged particles between eighty and a hundred-and-twenty miles above the earth
The atmosphere – which carries varying amounts of dust, water vapor and other particles
It is in the ionosphere though that the greatest distortion of the GPS monitoring signal is likely, due to high-energy particles radiated from the sun, most of all during the ‘solar cycle’.
GPS Monitoring and The Solar Cycle
The solar cycle that reached its climax in the years 2011/2012 occurred roughly every ten years causing at best, minor inconvenience to people who rely on the global positioning system. At worst, widespread disruption occurs, with even satellites themselves becoming disabled.
Imagine motorists in half the world lost and forlorn with their ‘Tom Tom’ or ‘Garmin’ GPS devices out of action and no map in the car’s glove-box. Doubtless the very least of many other rather greater potential misfortunes.
The sun’s solar flares and magnetic storms are intensified during the solar cycle, but at present scientists need to spot the flare-up on the sun before they can issue warnings, by which time charged particles are already on their way to earth.
However, NASA’s Solar Dynamics Observatory was sent into space on February 11, 2010 on a mission to gather data on the sun’s magnetic field activity and space weather, so that scientists may soon be better able to forecast the influence of solar flares and magnetic storms on the GPS monitoring system.
GPS Monitoring Reliability
All satellites are constantly monitored for errors in their position, altitude and speed by the USA’s Department of Defense from ground stations around the world.
The NOAA Space Weather Prediction Center provides alerts and advisory bulletins to users of GPS monitoring devices, which it is always wise to check before putting absolute confidence in the reliability of the global positioning system, especially during the solar cycle.
Sunspot is Sign of New Solar Cycle
The National Oceanic and Atmospheric Administration (NOAA) announced earlier the beginning of a new 11-year cycle of increased solar activity that could increase risk of failure to power grids, communications systems, and GPS monitoring navigation signals in its earlier press release. The first sunspot marking the beginning of the new solar cycle was observed on 3 January 2008.
What is a Sunspot? – Sunspots are regions of organized magnetic activity that show up as dark splotches on the sun’s surface. The number of sunspots visible on the surface of the sun is a measure of solar cycle intensity. As sunspots increase, the likelihood of major solar storms also increases. During these solar storms, highly charged matter from coronal mass ejections and energized protons from solar flares are launched at high speeds towards earth.
What is a Solar Cycle? – The number of visible sunspots on the sun’s surface rise and fall in a regular 11-year cycle. This newest cycle is based on the observation of sunspot number 10,981 that is located at a high sun latitude. NOAA began counting individual sunspots in 1972. This is the 24th cycle to be observed and is known as Solar Cycle 24.
What is the Effect of Solar Storms? – Energized matter and photons from solar storms strike the earth’s ionosphere and magnetic fields. These are the storms that cause northern or southern lights, the auroras. Some impacts include:
Long stretches of power transmission lines as subject to induction from solar storm energy. These extra electrical loads can overload power grids
Astronauts working in space can be harmed by solar generated radiation
Radio communications depend on having unimpeded transmission through the atmosphere. Strong solar storms can effect radio and cell phone transmissions.
Disruptions to the ionosphere can have a major impact on satellite transmissions of television, telephone and GPS navigation signals
NOAA Administrator Vice Admiral Conrad C. Lautenbacher, Jr. says, “Our growing dependence on highly sophisticated, space-based technologies means we are far more vulnerable to space weather today than in the past. NOAA’s space weather monitoring and forecasts are critical for the nation’s ability to function smoothly during solar disturbances.”
The NOAA Space Weather Prediction Center (SWPC) watches for solar activity and is the first line agency responsible for warning of severe solar storms and their consequences. The center provides space weather forecasts that are vital to reliable operation of communication and power systems. The prediction center also serves as the warning agency of an 11-nation consortium known as the International Space Environment Service (ISES).