The Global Positioning System (GPS) is a satellite constellation that provides very precise positioning, navigation, and timing (PNT) data around the globe.
Precision agriculture, driverless cars, maritime or aerial surveys, and military applications have all benefited from GPS, which was one of the earliest satellite positioning systems.
In this article, we’ll go over what GPS is, how it works, the distinctions between GPS and other satellite systems such as Global Navigation Satellite Systems (GNSS), and the equipment and applications that GPS enables.
Our book, An Introduction to GNSS, has further information on GPS and satellite technology.
What Exactly is GPS?
GPS is one of numerous global navigation satellite systems (GNSS) that provide positioning, navigation, and timing (PNT) data.
GPS is a global positioning system that is managed by the United States Space Force, a part of the United States Armed Forces.
GPS was established in 1973, with the first satellite launched in 1978.
Blocks of satellites are constructed and deployed in sequence.
Between 1978 and 1981, ten Block I GPS satellites were launched.
Beginning in 1989, the Block II class satellites were capable of transmitting on two L-Band radio frequencies.
Block IIA, IIR, IIR-M, and IIF were all developmental series for GPS’ Block II.
Block III was the culmination of a series of satellites that expanded on prior designs and capabilities.
The Block IIIA series of GPS satellites introduces additional signals and increased broadcasting power to the third generation of GPS satellites.
In 2018, the first of ten IIIA satellites was launched.
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What Is The Meaning Of GPS?
The Global Positioning System (GPS) is an acronym for Global Positioning System.
It’s also often used to refer to the positioning system itself, such as the built-in GPS in your car.
What Is GPS And How Does It Work?
The space segment, control segment, and user segment are the three primary segments of GPS, as with many other GNSS constellations.
The US Space Force operates and maintains approximately 30 satellites in orbit that make up the GPS space segment.
These satellites provide radio signals to Earth-based control and monitoring stations, as well as to customers that need very accurate satellite placement.
The GPS control section is also overseen by the US Space Force.
It consists of master and backup control stations, specialized ground antennas, and a number of monitor stations spread around the globe.
These stations monitor GPS satellites to verify they are in good working order, orbit in the right positions, and have accurate atomic clocks on board.
These stations are critical to the GPS constellation’s general health and accuracy.
Everyone who uses GPS satellites for PNT measurements falls within the user group.
Many applications employ GPS for high precision location and accuracy across the globe, from a mobile phone giving instructions to autonomous cars needing lane-level positioning accuracy; from a farmer recording planting and harvesting routes year over year to a UAV mapping a rainforest.
What Are GPS (Global Positioning System) Satellite Signals?
Satellites communicate their orbital position and precise time at that location on radio waves all the time.
This signal, together with at least three additional satellite signals, is received by antennas and processed in a GPS receiver to determine a user’s position.
GPS transmits on civilian frequencies L1 (1575.42 MHz), L2 (1227.60 MHz), and L5 (1176.45 MHz); GPS also broadcasts on governmental and regional satellite-based augmentation systems on L3 (1381.05 MHz) and L4 (1379.913 MHz) (SBAS).
Several satellites also transmit M-code, a military code that runs on the L1 and L2 frequencies and is only available to the US military.
What Exactly is M-code?
The M-code signal is a GPS-specific signal sent to assist the US Department of Defense.
With the launch of the Block IIR-M satellite in 2005, this signal was first transmitted.
Through 21 M-code-capable GPS satellites, M-code offers a layer of protection against jamming interference.
M-code uses the current GPS L1 and L2 L-Band frequencies, however it is modulated such that it does not interfere with L1/L2 transmissions.
Military receivers may calculate PNT only using M-code.
M-code is also used in military applications to boost the strength of L1 and L2 signals, making them more resilient to interference, jamming, and spoofing.
Although GPS signals are still vulnerable to jamming, M-code adds an extra degree of protection.
Many further layers of anti-jamming defenses are required to develop reliable PNT on GPS systems.
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GPS Precision
The processor in a positioning system determines how good it is.
A high-precision GPS receiver, for example, will be significantly more precise than a mobile phone.
To improve accuracy, potential causes of errors are identified and modeled at monitoring and control stations.
Clock inaccuracies, orbital drift, atmospheric and multipath delays, and radio frequency interference account for the majority of mistakes.
By contributing to geometric dilution of precision, these sources continually jeopardize positioning, navigation, and timing accuracy.
Subscriptions to GNSS/GPS correction services, SBAS, and the integration of additional sensors like inertial navigation systems or radar are some of the technologies that assist offset dilution of accuracy and these inaccuracies.
Different techniques used by more accurate GPS receivers to compute a location using pseudorange or carrier wave calculations can assist decrease mistakes.
What Is The Difference Between GPS And GNSS?
The term “global navigation satellite system” (GNSS) refers to all satellite constellations in orbit; GPS is one of numerous constellations that make up GNSS.
Many constellations make up GNSS, from GPS to GLONASS (managed by Russia’s Roscosmos State Corporation for Space Activities).
To deliver precise and dependable PNT, positioning technology depends on a variety of constellations.
Instead of comparing GNSS and GPS, it’s more useful to evaluate how GPS compares to other GNSS constellations.
GPS’s Applications
GPS provides applications that depend on satellite technology for precise location, navigation, and timing measurements all over the globe.
The necessity for a precise location, dependable and safe navigation, tracking and monitoring an object’s movement, surveying and mapping of an area, or timing within a billionth of a second drives the usage of GPS in these applications.
Mining applications, for example, use GPS to assess a region before starting operations.
Companies keep track of possible mineral reserves, determine which regions to avoid in order to reduce environmental effect, and allow autonomous equipment to transfer materials around the site.
GPS is used in conjunction with other constellations in applications that need high-precision location.
The US military, on the other hand, uses GPS in a unique manner because of its encrypted M-code signal.
M-code allows the military to maintain continuous access to positions while also increasing resistance to jamming and interference sources.
GPS Hardware And Software
GPS technology allows the precise PNT measurements required in various sectors’ solutions and applications.
GPS is essential for dependable location, safe navigation, and very precise timing in a variety of applications, including military, mining, agricultural, and commercial maritime.
The specific equipment and solutions that GPS technology allows are detailed in Chapter 8 of our Introduction to GNSS book, and we’ll mention a few examples below.
The antenna is the next most crucial piece of technology after the GPS receiver that calculates your PNT.
Only high-quality satellite signals are received for precise computations, therefore a GPS/GNSS antenna works as a gatekeeper.
GNSS/GPS correction services, which may correct multipath, timing, and atmospheric problems, are used to enhance these estimates.
Antennas and correction services are both important GPS technologies that enable GPS applications all around the globe.
Anti-jam antennas from GPS Anti-Jam Technology (GAJT) defend GPS and other satellite signals against interference, jamming, and spoofing.
M-code signals only give the bare minimum of anti-jamming protection, but GAJT and other anti-jamming solutions increase a system’s resilience and robustness for guaranteed PNT.
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How GPS Enables Precise Positioning, Navigation, And Time
We’ve covered what GPS is, how it works, and how it’s used to support applications all around the globe in this post.
The Global Positioning System (GPS) was one of the first satellite positioning systems to be built, and its innovations continue to assist the development and use of positioning technology to this day.
GPS will remain at the heart of daily life as GPS-based autonomous applications grow increasingly prevalent.
