The Global Positioning System (GPS) was created by the US Department of Defense to answer the second most important question an army has: "Where are we?" (The most important question being: "Where's the chow line?")
Today, GPS satellites constantly send signals ground-ward; these signals are picked up by GPS receivers, which calculate position. It didn't take long for police and fire departments, construction crews and other civilian operations to see the value of GPS.
For consumers, the industry needed to refine GPS tracking system into user-friendly, consumer electronics. For example, it does little good to know you're at 40 degrees 33 minutes 24 seconds north 118 degrees 48 minutes 36 seconds west, unless you already know that's where Overstock.com is located and you're trying to parachute onto the office roof. So, manufacturers added street by street visual directions.
The Global Position System has three sectors:
Satellites
Twenty-four active plus five standby satellites orbit the Earth twice each day. At least four should be 'visible' to the ground at all times, allowing GPS tracking system users to precisely determine latitude, longitude and altitude.
Command and control system
Currently under the direction of the Air Force Space Command, certain areas are managed by other agencies, such as the Coast Guard Navigation Center (for maritime issues).
GPS receivers
GPS units are receive-only electronics; they do not transmit data or interact with other sectors of the system. This allows an unlimited number of simultaneous users. In other words, this may be the only operation of the US government that is available 24/7 and will never put you on hold!
Consider its use before buying a GPS unit:
Car GPS
Probably the most popular application, all car GPS units include street maps; high-end models offer turn-by-turn voice instructions. Frills include touch screen operation, cell phone connectivity, video games, radio, CD or DVD players and computer links to receive software updates.
Cell phone GPS
Mandated in the aftermath of September 11th, the Federal Communication Commission (FCC) required cell service providers to make GPS tracking of cell phone calls possible. All phones made since 2005 are GPS-trackable. Cell phones including handheld GPS receivers are also available, but may not operate properly if you are outside your cell providers' service area.
Recreational GPS
Wrist, armband and handheld GPS units are especially good for hikers and bikers.
Marine GPS
Marine GPS is, of course, waterproof (most electronics don't react well to water!) and they float--not a feature you actually want to use, but most welcome should extreme circumstances arise. Ocean maps are notoriously dull to read, but shoreline maps and features like tide tables and fish-finders can be very useful. Marine GPS tracking is especially valuable when entering or exiting crowded harbors.
GPS accessories and add-ons enhance their use:
Maps
GPS units have factory installed street maps of the United States. World travelers can purchase additional GPS system maps of Canada and other areas.
Data storage
GPS users can store even more if the device supports removable memory cards like those commonly used for digital cameras.
Combo packs
For most people, GPS receivers work great on their own. For the serious user/traveler, portable GPS devices are available with personal digital assistants (PDAs) and two-way radios built in. As noted, car GPS units can also include entertainment or media extras.
GPS holders
These attach to the car dashboard or console so your handheld GPS doesn't have to be handheld while driving.
GPS antennas
These amplify GPS signals and are especially useful in urban areas where there is more chance of interference from terrestrial sources.
GPS chargers
Obviously, a handheld GPS must be recharged; at home and car adapters are available.
Some GPS terminology:
Nationwide Differential Global Positioning System
Commercial GPS receivers are almost always on target to within about 50 feet, but many users see accuracy to within 30 feet. NDGPS is a joint Transportation-Commerce-Homeland Security program using fixed, land-based reference stations. When near an NDGPS marker, GPS accuracy may increase to less than 10 feet.
Geocaching
Geocaching (pronounced /GE-oh-CASH-ing/) is a new and exciting game gaining popularity every year--a sport that exercises the mind and body. Simply put, it's GPS hide-n-seek; gamers place objects ranging in size from a 35-mm film can to a military ammo box in plain sight. The locations (latitude and longitude) are logged onto web sites. Players use their GPS units to locate the caches or 'waypoints'. It's a whole lot harder than it sounds. Waypoints can be disguised as plants or rocks and getting within 30 feet still leaves a lot of ground to cover. Some waypoints are pick-n-place, meaning they have prizes inside; when you find one, trade a trinket you bring for a trinket you find.
Benchmarks
One early means of determining locations was small metal markers placed by the Commerce Department's National Geodetic Survey (NGS). These are still in place and are found all over the US on street corners, mountain tops, in parks and other obvious and not so obvious places. All benchmark locations are logged and available from the NGS. They can be a quick test to see if your GPS unit is working properly or for geocaching.
Question--can the government really track me through my cell phone?
Not only the government, GPS tracking via cell phone is a commercial service available for parents (to keep tabs on their children), business owners (to track delivery vans and employees) and others (even pet owners can hook a GPS receiver to their pets, in case Rover lives up to his name). Safety, quality of service and fraud prevention have been recognized by courts as legitimate use of GPS tracking systems for surveillance by non-government entities.
GPS tracking abuse and misuse are inevitable, but that's true of every modern convenience--for the positives of GPS, there are also a few negatives. However, the day your son, daughter or $100,000 load of someone else's property goes missing, you definitely won't be screaming "Invasion of privacy!" at the FCC.
Caring for GPS units:
Dust, heat, humidity and impact damage are primary causes of failure. Don't drop your GPS unit, not even onto something soft like water--especially not onto something soft like water!
Wipe it down with a clean cloth before you put it away and, if your GPS receiver has openings like a data card slot or battery compartment, blow those clean with canned air--never your humid breath.
If you own a car GPS system, mount it out of direct sunlight. Even on cool days, the dashboard can get dangerously hot for electronics and excessive exposure to the sun's radiation can damage the memory--yes, sunburn can be terminal for a GPS terminal.
Like all modern consumer electronics, a GPS receiver has few moving parts to break, so it can provide years of valuable service (and a whole lot of fun!) if not abused. Enjoy!
