Core Navigation System

FIELDS OF STUDY: Space Technology; Astronautics

ABSTRACT: Core navigation systems are used to direct and track vehicles and people as they move from one location to another. A range of instruments and tools have been developed for this purpose, including systems that use information relayed from satellites in space to determine position both in space and on Earth. These systems are important because they make locating and directing vehicles and people in real time easy and accurate.

The concept of navigation can be viewed as both a science and an art. In the scientific view, navigation is a means of determining an object’s position and speed in relation to a set point in space. The art of navigation involves determining how to get from one point to another while avoiding as many obstacles as possible.

In the past, travelers used the positions of the sun, moon, and stars to determine their geographic location as well as the time of day. Eventually, instruments such as astrolabes and compasses were created to help refine the navigation process, making it easier to accurately determine and plot a course. Accurate clocks became invaluable for establishing speed and location.

As technology improved, navigational equipment also became more advanced. Navigation based on triangulation of radio signals became popular in the early twentieth century. However, land-based systems had limited accuracy and did not work everywhere. With the advent of space travel in the mid-twentieth century, researchers began work on a new generation of tools. Satellites made it possible to transmit radio signals anywhere. A web of satellites encircling the Earth could send information to a specially equipped receiver, enabling it to precisely determine its location. Multiple readings could establish how fast and in what direction the receiver was traveling. This also made it possible to look ahead of the receiver’s projected path and plot a course that would fulfill any of a range of variables. Computers made these calculations far more quickly and accurately than a human could. Scientists sought to create a core navigation system that would more completely automate the navigation process. Research continues to upgrade technologies like mobile robot navigation systems. It has several applications, including in areas like rescue robots and transportation. The remote sensing method Light Detection and Ranging (LIDAR) has worked independently compared to Global Positioning System (GPS). LIDAR can also be coupled with other systems like the inertial navigation system, GPS, and camera.

In the mid-1990s, the United States and Russia established the first satellite navigation systems that provided complete coverage of any location on the planet. Subsequently, China and the European Union also placed satellites in orbit with the intent of covering the entire globe, while several other countries pursued regional satellite navigation systems to cover certain areas.

The United States initiated its Navigation Signal Timing and Ranging, or Navstar, Global Positioning System (GPS) in the 1970s. It was intended to consolidate the growing number of navigation systems used by the US military. The first satellite for this system was launched in 1974. By the mid-1980s, enough satellites were in orbit to make the system functional for some uses. The full array of twenty-four satellites was completed in 1993, and fully operational worldwide coverage was achieved by 1995. GPS was also made available to the public as well as the military. By 2021, a total of thirty-one satellites were available for use as part of the GPS. The full array of satellites is called a constellation.

At least twenty-four satellites are operational at any given time. Twice a day, these satellites circle Earth in overlapping orbits at a distance of about 20,200 kilometers (12,550 miles) above the planet’s surface. The satellites are programmed to send signals at exactly the same time. Receivers can tell their distance, latitude, longitude, and time based on how long it takes a signal to travel from the satellite to the receiver. The satellites are calibrated and synchronized so precisely that a GPS-enabled device can triangulate its position to within a few meters or even centimeters of its actual location, depending on the sophistication of the device. The Federal Aviation Administration (FAA) has reported that even their most basic receivers have an accuracy within 7.8 meters (about 25.6 feet).

The satellites constitute the space segment of the GPS, one of three components that make up the overall system. Another portion, the command segment, keeps track of the satellites and their information. From numerous bases on Earth, US Air Force personnel coordinate, analyze, and synchronize the data flowing to and from the GPS satellites and monitor their maintenance needs. These tasks are controlled by the Master Control Station in Colorado. There are also a number of monitoring stations around the world that track the satellites as they pass overhead, gathering and sending data to ensure the system remains operational. In addition, information is gathered from a number of ground antennas that are also part of the monitoring and command system.

The space and command segments of the system are controlled and monitored by the United States government. The final component of the system, the user segment, is in the hands of individuals and companies. The GPS is available free for use by all, and this has led to the development of thousands of devices that allow for the tracking of everything from vehicles and shipping containers to cell phones. In most cases, users do not need to know anything about where the satellites are or how they work. They merely need to turn on their receivers to benefit from the automated navigation system.

Though GPS is the most widely used core navigation system, others are also in use or development. Russia maintains the GLONASS system that functions similarly to GPS. The European Union’s Galileo global satellite navigation system and China’s BeiDou system became fully operational by 2020.

Applications of Core Navigation Systems

Satellite navigation systems were originally conceived and designed for military use. In the twenty-first century, satellite navigation is used to assist with weapons firing, supply and troop deployment, search-and-rescue maneuvers, and other military operations. Some US military vehicles are equipped to operate without human direction, relying totally on GPS navigation for guidance.

Because the US military has become so dependent on GPS for so many operations, it carefully protects its core system. The GPS used in civilian applications is not as precise as the military system. Military GPS transmissions are also encoded differently to prevent people with civilian equipment from jamming or taking over the system.

As GPS and its capabilities grew, commercial applications for it increased. In the 1980s, scientists began using handheld units to provide precise locations for archaeological and geological research sites. In 1989, the first handheld units for hikers, boaters, and other outdoor enthusiasts became available. As awareness of the technology grew, so did the demand. By the 2000s, small, portable units were available for use by motorists. Within a few years, GPS technology was being built into everything from automobiles and farming equipment to electronic tablets and cell phones.

While some applications of a core navigation system are more of a convenience, others increase safety and save lives. First responders such as fire, police, ambulance, and rescue workers can use GPS to more precisely locate given addresses or vehicles with onboard navigation systems. This enables them to arrive more quickly when help is needed, with fewer delays caused by misdirection, saving lives in the process. Drivers of ride-sharing service providers, such as Uber, depend on GPS to track customers’ location. Home delivery service providers also use GPS to track the address of customers. Researchers have invented an artificial intelligence (AI)-based model that uses satellite imagery to tag road features in digital maps. It is called RoadTagger and uses neural network architectures that can help improve GPS navigation. RoadTagger also helps predict features such as bike lanes and parking spots.

GPS has also greatly improved the accuracy of spacecraft navigation. Early space probes that used other navigation systems were hard to track, making precise missions difficult. GPS allowed better calculation of position and ability to set a specific course. Between the 1960s and 2012, the accuracy with which a spacecraft could be tracked increased by a factor of one hundred thousand.

PRINCIPAL TERMS

  • GPS: the Global Positioning System (GPS), a network of satellites and Earth-based control stations used to determine the location, direction, and speed of objects. Established and maintained by the US government, it can be accessed freely with any GPS receiver device.
  • satellite navigation: a system of navigation in which location is determined based on information transmitted from satellites. A receiver records the time of regular transmissions from multiple satellites equipped with atomic clocks, allowing it to determine its longitude, latitude, altitude, and time.

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