Preventing GPS Disasters

If your GPS device told you do drive off a cliff or ford a raging river, would you do it? You may respond, of course not, that’s stupid. Unfortunately, many people substitute technology for common sense, often with tragic results.

Satellite navigation systems are changing the way in which we navigate from place to place by land, sea or air; in remote wilderness areas or through congested urban streets. The GPS system has been called the greatest advance in outdoor navigation since the invention of the compass and has become a widely used aid to navigation worldwide, a useful tool for map-making, land surveying and recreational navigation. An estimated 50 million navigation devices, including in-car systems, handheld or portable units and smart phones, will be in use in the United States this year.

Whether you're prospecting, hunting, fishing, cross-country skiing, or taking a hike in the back country, a GPS receiver can help you reach your destination and return safely - but only if you know how to accurately use it and recognize its limitations.

The Global Positioning System (GPS) is a satellite-based navigation system made up of a complex network of more than 30 satellites placed into orbit by the U.S. Department of Defense. The GPS network, also called NAVSTAR, was originally intended for military applications, however when Korean Air Lines Flight 007 was shot down in 1983 after straying into the USSR's prohibited airspace, President Ronald Reagan issued a directive making GPS freely available for civilian use as a common good. The GPS works all the time, in any weather condition, anywhere in the world, 24 hours a day.

Powered by solar energy, the numerous satellites that make up the GPS space segment orbit at approximately 12,000 miles above the earth. Moving constantly at speeds in excess of 7,000 mph, the satellites each make two complete orbits of the earth in less than twenty-four hours. The GPS satellites are kept on track by small rocket boosters. Primarily operated on solar power, the satellites also employ backup batteries in anticipation of power loss during a solar eclipse.

The first GPS satellite was sent into orbit in 1978, with a full constellation of satellites achieved in 1994. Weighing approximately 2,000 pounds, each satellite is about 17 feet across with the solar panels extended and is built to last about ten years. Replacement satellites are constantly being built and then launched into orbit.

GPS signals can be affected by multi-path issues, where the radio signals reflect off surrounding terrain such as tall buildings, mountains or large obstructions. This increases the travel time of the signal and can cause inaccuracy. The number of satellites visible, or the more satellites a GPS receiver can “see” will also affect accuracy. Electronic interference, buildings, terrain or sometimes even dense foliage can block the signal reception and cause positioning errors or prevent a position reading at all.

Anomalies like high static discharge during lightning storms, humidity, ionized air and barometric pressure can definitely cause false information, data error or miscalculations. A satellite signal slows as it passes through the atmosphere. Ionosphere and troposphere delays may cause distortion. GPS units normally will not work indoors, underground or underwater.

In automotive GPS receivers, metallic features in windshields, such as window tinting films or defrosters elements can degrade reception inside the vehicle. Receiver clock errors are also common. This type of error occurs because a receiver’s built in clock is not as accurate as the atomic clocks onboard the GPS satellites and will reflect varying timing errors. These distortions can result in positioning errors of hundreds of miles.

Unreliable data is also a major contributor to GPS errors. With an incalculable number of roads and millions of miles of ground to cover, it is impossible for any data system to be 100% accurate. A road network is a constantly changing entity; roads are diverted or closed, construction reroutes traffic while weather affects road conditions. The data feed used in GPS units is dated. Fresh updated content may not be available for several months. It is important to remember that this data is updated quarterly at best and in some cases only released twice a year.

Although GPS Navigation is becoming increasingly popular, these units have the ability to highlight human error. A GPS devise will attempt to advise you depending on the destination your have entered. An incorrect address or a mistake in spelling are common errors. Instead of making our lives easier, some of these devices are so technologically enhanced they are very difficult to use. User mistakes account for the majority of GPS errors, however a GPS receiver has no way to identify and correct these mistakes.

GPS technology isn’t perfect! It’s imperative to pair its directions with a healthy dose of common sense. Many drivers exhibit a surprising willingness to rely on gadgets instead of experience. They are finding that satellite navigation may replace paper maps, however following the GPS’s not always reliable directions, many users are getting hopelessly lost, hitting dead ends or road closures and even swerving into oncoming traffic.

Even if you are not blindly following erroneous, computer-generated instructions, research studies tell us that “using GPS while behind the wheel is actually more distracting and less safe than unfolding a paper map and using it to find your way”. A large portion of drivers, according to the study, relied exclusively on their GPS unit for directions, “rendering them completely oblivious to the world around them”.