The Global Positioning System (GPS) is a radionavigation system developed by agencies of the United States government which is designed to provide users with a three-dimensional positioning system. A series of 24 satellites maintained by the U.S. and distributed in six orbital planes communicate with monitoring stations on the Earth’s surface and the wide multitude of GPS signals found in millions of electronic devices all over the world. The latest GPS performance standard indicates that the current state of the technology achieves a horizontal accuracy of 3 meters (9.8 feet) or better and a vertical accuracy of 5 meters (16.4 feet) or better 95 percent of the time.
However, despite the maximum theoretical accuracy of GPS, many issues persist. Time-keeping issues experienced by many receivers can cause calculated positions to drift from a receiver’s actual position, a problem which can become truly frustrating when relying on GPS positioning for driving navigation tools. Incorporating atomic clocks into GPS receivers would alleviate the problem, but that would also add about $100,000 to the cost of every GPS-enabled device. A more cost-effective solution involves the use of mathematical algorithms designed to accommodate for time-keeping errors. But GPS is deficient as a positioning system in other ways as well; for example, satellite signals often have a difficult time penetrating thick walls to reach a receiver positioned within a building.
Many of these issues would be addressed by a new ground-based GPS system being developed by an Australian tech firm in collaboration with both NASA and the U.S. Air Force. Locata, headquartered in the Australian Capital Territory city of Bruce, has designed ground-based transmitters which can provide accurate positioning by blanketing a vicinity with radio signals. NASA has seen some success in integrating the technology into unmanned aircraft safety systems while the Air Force is using the radio signal technology to monitor warfare simulation facilities in New Mexico. Signal synchronization timing is about 50 times quicker than conventional GPS and the proximity of these Earth-based sensors to receivers mean that signals can be more easily detected through walls.
The foundation of the modern-day GPS system we use today to find our location through mobile apps began to be built in 1978, when the U.S. Department of Defense launched its first Navigation System with Timing and Ranging (NAVSTAR) satellite. 23 more satellites would be launched in the coming years and the satellite-based navigation system envisioned by the DoD became a reality in 1993. Two levels of service are provided by current GPS technologies: the Precise Positioning Service (PPS), use of which is restricted to U.S. military and other federal agencies; and the Standard Positioning Service (SPS), which is freely available on a worldwide basis without direct user charges.
An array of augmentation systems exist which serve to improve aspects of GPS including accuracy, availability or signal timing, and a variety of federal agencies have implemented such GPS augmentation. The Nationwide Differential GPS Service (NDGPS) has been operated since 1999 by the U.S. Coast Guard in conjunction with the U.S. Department of Transportation and the U.S. Army Corps of Engineers. The NDGPS system is comprised of one control center and 84 remote broadcast sites, improving accuracy to GPS-derived positions by broadcasting correction signals on marine radiobeacon frequencies. NASA’s Jet Propulsion Laboratory is behind the development of the Global Differential GPS (GDGPS) System. The GDGPS is the world’s largest real-time tracking network and collects positioning data processed by software which is designed to derive differential corrections to satellite orbit and clock states. Heavy system redundancies result in low latency times and uninterrupted customer service.
The federal government of the United States has been committed to a policy of making GPS available to the civilian community at the level dictated by performance standards which are regularly updated every few years; this is especially true in the years since policies leaning towards selective availability, which involved the intentional degradation of signals, were discontinued in 2000. The U.S. quest for dominance in satellite navigation systems has also led to a policy of modernizing the nation’s GPS through at least 2025. The current state of the art in GPS satellites is the GPS IIF satellite, developed by the Boeing Company (NYSE:BA) for a government contract. A total of 12 GPS IIF satellites, which have advanced atomic clocks and a 12-year lifespan, have completed production and will launch by the end of 2016; as of December 11th, 2015, there were a total of 31 satellites which were operational for GPS purposes. The next generation of GPS satellites, the GPS III, is already under development by the Lockheed Martin Corporation (NYSE:LMT) and will be designed for a 15-year lifespan and have enhanced functions for global search-and-rescue as well as increased signal reliability.
Improvements to the Earth-bound control segment of GPS have also been important in increasing the accessibility of GPS for consumers all over the world. Beginning in 2007, the Air Force began implementing what was known as the Architecture Evolution Plan (AEP), a project to replace the system’s mainframe-based master control station with more modern information technologies through 2019. In February 2010, an Air Force contract was awarded to the Raytheon Company (NYSE:RTN) to construct the Next Generation Operational Control System (OCX). The new control station would be compatible with GPS III as well as legacy satellites and is being designed so that it can continue to operate in the event of a cyber attack. GPS III satellites will be put into orbit by the Launch Checkout Capability command and control center, components of which are being developed by both Raytheon and Lockheed, which will provide satellite launching capabilities for the new generation OCX.
Many of the technological improvements made to GPS are made to increase the number of signal channels available for civilian operations. For example, in recent years the U.S. government has added civil signal channels at designated frequencies intended to serve in applications such as high-precision science as well as critical safety systems for civil aviation. Civil signals are expected to support billions of dollars worth of economic productivity in the coming years and even reduce fuel costs for a range of transportation options, from railway vehicles to airplanes.
Private commercial interests have shown the ability over the years to take the basic GPS positioning system made available to consumers all over the world and improve upon it for applications requiring a high degree of accuracy. Many of these systems for improved accuracy are intended for use with unmanned aerial vehicles (UAVs), or drones, for which operators desire highly precise spatial measurements for vertical and horizontal positioning. San Francisco-based firm Swift Navigation has developed a real-time kinematics (RTK) GPS receiver capable of producing location measurements which are accurate to within inches. The Piski receiver developed by Swift Navigation incorporates a system which cross-checks signal wavelengths against a reference database to return incredibly precise location services.
Elsewhere, academic research facilities are also involved in developing enhanced technologies. Scientists working at the University of Texas at Austin have developed a software program which, when working in conjunction with GPS receivers that are only slightly better than those found standard in most smartphones, can provide positioning data down to the order of centimeters. The algorithm developed by UT researchers works against some of the more common signal interference problems and could eventually be designed to run on a smartphone’s CPU and not require a dedicated remote server.