Space is the new frontier for useful and playful high-tech consumer gadgetry, as satellite technology developed for the military comes into its own running a burgeoning variety of portable devices that let people know where the heck they are.

Personal use of the U.S. military's Global Positioning System (GPS) constellation of satellites has matured into a rapidly growing multibillion-dollar industry. Sales will reach $22 billion in 2008, according to ABI, a New York-based technology market research firm.

GPS capability is being added to cars, trucks, handheld PDAs and even cell phones. New applications on the rise include people and asset tracking, automatic vehicle location, and recreational use, ABI reported last month.

"GPS has enabled a host of new telematics applications, from tracking a teen's use of the family car to automatic tax collection for interstate trucking companies," said Frank Viquez, ABI's director of automotive electronics.

Cutting-edge manufacturers -- Garmin, Magellan, Trimble, Lowrance and many others -- are cranking out scads of innovative high-tech products to meet growing demand.

The fast-paced nature of the business is evidenced by contrasting the first GPS-based survey receiver -- as big as a refrigerator and tallying upwards of $100,000 -- to today's palm-sized units that can be had for as little as $100.

The first GPS -- a developmental satellite -- was launched in 1978.

The U.S. Department of Defense (DoD) runs this worldwide radio-navigation system, originally developed for defense military purposes as a way to precisely locate objects anywhere on Earth. The original price tag to develop the satellite system was a hefty $12 billion.

In war-fighting arenas, GPS has a proven track record. For instance, in the first six days of the U.S.-led Operation Iraqi Freedom, more than 80 percent of the munitions that hit several thousand targets were precision-guided via GPS.

The system, comprised of six different rings of satellites circling Earth, provides exact navigational latitude, longitude, altitude, velocity and precise time information around the clock.

This strategic pattern allows a ground-bound receiver to snag a signal from at least four different satellites.

A GPS satellite emits a continuous navigation signal and orbits Earth every 12 hours. The system is so accurate that time can be figured to within 25 billionths of a second, velocity within a fraction of a mile per hour and location to within 16 meters, or about 52 feet.

The U.S. government made the system available for civilian use in the 1980s. At first, the consumer version of the service was less precise than the military one.

In May 2000, then President Bill Clinton decreed that the United States would stop the intentional degradation of the GPS signals available to the public -- a process called Selective Availability (SA). This meant that civilian users of GPS would be able to pinpoint locations up to ten times more accurately than previously possible.

"GPS has become a global utility," Clinton said at the time. "It benefits users around the world in many different applications, including air, road, marine, and rail navigation, telecommunications, emergency response, oil exploration, mining, and many more. Civilian users will realize a dramatic improvement in GPS accuracy with the discontinuation of SA."

Over the last few years, commercial utilization of GPS has blossomed as product prices have plummeted.

GPS satellites circle the planet twice a day in very precise orbits and transmit signal information to Earth. Each satellite totes an atomic clock, permitting it to send out a signal at regular, exact intervals. GPS receivers take this information and use triangulation to calculate an exact surface location.

The entire system operating at present consists of 28 satellites.

A GPS receiver compares the time a signal was transmitted by a satellite with the time it was received. The time difference tells the GPS receiver how far away the satellite is. With distance measurements from multiple satellites, the receiver can determine the user's position.

A receiver must be locked on to the signal of at least three satellites to calculate a two-dimensional position -- latitude and longitude -- and track movement.

With four or more satellites in view, the receiver can determine the user's 3D position (latitude, longitude and altitude). Once the user's position has been determined, a GPS unit can calculate other information, such as speed, bearing, track, trip distance, distance to destination, even sunrise and sunset time.

Typically, GPS receivers maintain strong locks, despite dense foliage, or even for those buried in an urban setting. Some atmospheric factors and other sources of error can affect the accuracy of GPS receivers, however. The signals essentially travel by line of sight -- they will pass through clouds, glass and plastic but will not go through most solid objects such as buildings or mountains.

A GPS signal contains three different bits of information -- a pseudorandom code, ephemeris data and almanac data.

• The pseudorandom code is simply an I.D. code that identifies which satellite is transmitting information.
• Ephemeris data, which is constantly transmitted by each satellite, contains important information about the status of the satellite (healthy or unhealthy), current date and time. This part of the signal is essential for determining a position.
• The almanac data tells the receiver where each GPS satellite should be at any time throughout the day. Each satellite transmits almanac data showing the orbital information for that satellite and for every other satellite in the system.

Varying types of GPS receivers are built to match particular needs, from serious sporting to casual hiking or biking, from sailing around the world to off-road 4-wheeling or just getting around town.

Real-world applications of GPS fall into five broad categories:

• Location - determining a basic position
• Navigation - getting from one location to another
• Tracking - monitoring the movement of people and things
• Mapping - creating maps of the world
• Timing - bringing precise timing to the world

One new product recently announced comes from Trimble, headquartered in Sunnyvale, California: An AgGPS Autopilot system. This automated steering setup uses GPS technology to guide agriculture vehicles in consistent rows for tilling, spraying and applying fertilizers.

Trimble says the AgGPS Autopilot system saves time and money. It reduces driver fatigue, eliminates guessing about rows, reduces soil compaction, and allows around-the-clock operations. Most importantly, the system increases efficiency to lower the net cost per acre.

Another leading producer of GPS products is Garmin International Inc., with U.S. offices in Olathe, Kansas. Their products are used in flying, boating, driving, hiking, and other activities.

"Garmin has two markets in which it operates -- the aviation market and consumer GPS market," said Pete Brumbaugh, a company spokesman. "The latter has been growing at a clip of 20-25 percent per quarter in revenue over the past 18 months. Within this market are several segments that comprise growth opportunities for Garmin, such as marine electronics, outdoor recreation products, automotive electronics, wireless communication devices and Personal Digital Assistants (PDAs). Nearly all of our products are GPS-enabled," he told SPACE.com.

Garmin introduced this year a lightweight personal training system.

"It figures average rate and distance covered during outdoor workouts and retains up to five years of fitness records in its internal memory," Brumbaugh said. "All data is GPS-derived, including rate of climb and calories burned."