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Global Navigation Satellite System (GNSS) receivers, using the GPS, GLONASS, Galileo or BeiDou system, are used in many applications. The first systems were developed in the 20th century, mainly to help military personnel find their way, but location awareness soon found many civilian applications.
Automobiles can be equipped with GNSS receivers at the factory or as aftermarket equipment. Units often display moving maps and information about location, speed, direction, and nearby streets and points of interest.
Heavy equipment can use GNSS in construction, mining and precision agriculture. The blades and buckets of construction equipment are controlled automatically in GNSS-based machine guidance systems. Agricultural equipment may use GNSS to steer automatically, or as a visual aid displayed on a screen for the driver. This is useful for controlled traffic and row crop operations and when spraying. Harvesters with yield monitors can also use GNSS to create a yield map of the paddock being harvested.
Cyclists often use GNSS in racing and touring. GNSS navigation allows cyclists to plot their course in advance and follow this course, which may include quieter, narrower streets, without having to stop frequently to refer to separate maps. GNSS receivers designed specifically for cycling may include 'street-aware' mapping features, or may be oriented towards recording the progress of the cyclist along the route. This data can be reviewed after the ride to inform the rider's training or competition planning, or uploaded to online services which allow riders to view and compare each other's rides.
Hikers, climbers, and even ordinary pedestrians in urban or rural environments can use GNSS to determine their position, with or without reference to separate maps. In isolated areas, the ability of GNSS to provide a precise position can greatly enhance the chances of rescue when climbers or hikers are disabled or lost (if they have a means of communication with rescue workers).
GNSS equipment for the visually impaired is available.
Boats and ships can use GNSS to navigate all of the world's lakes, seas and oceans. Maritime GNSS units include functions useful on water, such as "man overboard" (MOB) functions that allow instantly marking the location where a person has fallen overboard, which simplifies rescue efforts. GNSS may be connected to the ships self-steering gear and Chartplotters using the NMEA 0183 interface. GNSS can also improve the security of shipping traffic by enabling AIS.
Air navigation systems usually have a moving map display and are often connected to the autopilot for en-route navigation. Cockpit-mounted GNSS receivers and glass cockpits are appearing in general aviation aircraft of all sizes, using technologies such as SBAS or DGPS to increase accuracy. Many are certified for instrument flight rules navigation, and some can also be used for final approach and landing operations as in Joint precision approach and landing system. Glider pilots use GNSS Flight Recorders to log GNSS data verifying their arrival at turn points in gliding competitions, and for information to aid en route decision making for cross-country soaring.
Aircraft passengers: Most airlines allow passenger use of GNSS units on their flights, except during landing and take-off, when other electronic devices are also restricted. Even though consumer GNSS receivers have a minimal risk of interference, a few airlines disallow use of hand-held receivers during flight. Other airlines integrate aircraft tracking into the seat-back television entertainment system, available to all passengers even during takeoff and landing.
Spacecraft use GNSS as a navigational and timing tool. The addition of a GNSS receiver to a spacecraft allows precise orbit determination without a ground tracking station. This, in turn, enables autonomous spacecraft navigation, formation flying, and autonomous rendezvous.
The use of GNSS in low Earth orbit and lower sun-synchronous orbit is similar to use on Earth and in air as the powerful main lobe signals of the GNSS satellites can often be received. Orbcomm's constellation on LEO and SSO uses GPS receivers on all satellites. Affordable commercial off-the-shelf (COTS) receivers can be used as well, as demonstrated by China using low-cost COTS GPS/BDS receivers installed on Yaogan-30 (YG30; LEO) series and Fengyun-3C (FY3C; SSO) satellites. The more advanced dual-frequency receiver was precise to 10–15 cm while the cheaper single-frequency receiver was precise to 20 25cm. Using two systems at the same time enhances service availability on the polar orbit (SSO) of FY3C by making more satellites visible. In general, use of GNSS at altitudes less than 3000 km is considered to fall into the terrestrial service volume (TSV).
The use of GNSS in MEO, GEO, HEO, and highly elliptical orbits is more complicated due to reduced visibility of the main lobe. GNSS coverage above the TSV but up to the GEO (36,000 km) is known as the space service volume (SSV). The SSV is in turn divided into the lower SSV and the upper SSV at 8,000 km, the approximate height of GNSS orbits. Lower SSV receivers receive unobstructed views of more satellite's main lobes compared with the TSV; using omnidirectional antennas helps exploit this feature. The high Doppler shifts at lower SSV require adaptation of the positioning algorithm. Upper SSV receivers need to make do with the "spillover" of main lobe signal (i.e. the part not shadowed by Earth) and the much weaker (15 - 20 dB) side-lobe signals as well as deal with periods of no coverage. These design constraints (and possibly the radiation environment found in space) prevent the use of COTS receivers. Use of GNSS in SSV is largely mature.
Use of GNSS beyond the GEO is still experimental. The Magnetospheric Multiscale Mission demonstrated GPS use at 150,000 km altitude in 2018. The Lunar GNSS Receiver Experiment (LuGRE) onboard the Blue Ghost Mission 1 acquired and tracked GPS and Galileo at 400,000 km from Earth, in Lunar orbit. using a high-gain antenna pointing in the direction of Earth. It also acquired a realtime fix on lunar surface. After-the-fact analysis of LuGRE recordings found that other GNSS systems were also captured by the experiment and could be used to improve availability. At lunar distances, the plasmasphere may exert a significant effect on GNSS signals, in addition to the well-known ionospheric delay.
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GNSS is used in creation of maps using geographic information systems. Several projects, including OpenStreetMap and TierraWiki, allow users to create maps collaboratively, much like a wiki, using consumer-grade GPS receivers.
High precision measurements of crustal strain can be made with differential GNSS by finding the relative displacement between GNSS sensors. Multiple stations situated around an actively deforming area (such as a volcano or fault zone) can be used to find strain and ground movement. These measurements can then be used to interpret the cause of the deformation, such as a dike or sill beneath the surface of an active volcano. Real-time GNSS positioning can also be employed as part of earthquake early warning systems.
As archaeologists excavate a site, they generally make a three-dimensional map of the site, detailing where each artifact is found. High-precision GNSS makes this process simple.
Most mapping grade GNSS receivers use the carrier wave data from only the L1 frequency, but have a precise crystal oscillator which reduces errors related to receiver clock jitter. This allows positioning errors on the order of one meter or less in real-time, with a differential GNSS signal received using a separate radio receiver. By storing the carrier phase measurements and differentially post-processing the data, positioning errors on the order of 10 centimeters are possible with these receivers.
Survey-Grade GNSS receivers can be used to position survey markers, buildings, and road construction. These units use the signal from both the L1 and L2 GPS frequencies. Even though the L2 code data are encrypted, the signal's carrier wave enables correction of some ionospheric errors. These dual-frequency GPS receivers typically cost US$10,000 or more, but can have positioning errors on the order of one centimetre or less when used in carrier phase differential GPS mode. (The advent of L2 L5 civilian service has lead to widespread production of L1/L5 and L1/L2 dual-frequency GPS devices.)
Survey-grade GNSS receiver industry include a relatively small number of major players who specialize in the design of complex dual-frequency GNSS receivers capable of precise tracking of carrier phases for all or most of available signals in order to bring the accuracy of relative positioning down to cm-level values required by these applications. The most known companies are Javad, Leica, NovAtel, Septentrio, Topcon and Trimble.
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