Geopositioning

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Principles of geolocation using GPS Geolocation.png
Principles of geolocation using GPS

Geopositioning is the process of determining or estimating the geographic position of an object or a person. [1]

Contents

Geopositioning yields a set of geographic coordinates (such as latitude and longitude) in a given map datum; positions may also be expressed as a bearing and range from a known landmark. In turn, positions can determine a meaningful location, such as a street address.

Specific instances include:

Geopositioning, Geolocation, and Geofencing

Geopositioning is sometimes referred to as geolocation, and the process may also be described as geo-localization.

While these terms are often used interchangeably, they have slightly different meanings. Geolocation generally refers to the identification or estimation of the real-world geographic location of an object, often specifically in the context of digital or electronic systems, such as determining the location of a computer, mobile device, or network node.

Geofencing, on the other hand, involves creating a virtual geographic boundary (Geofence), enabling software to trigger a response when a device enters or leaves a particular area. [3]

Though these processes are closely related and are part of the broader concept of location-based technologies, they are distinct in their specific applications and functions. While geolocation typically provides a set of coordinates to localize an asset on a reference plan or on a map, geofencing can simply provide the range of distance or a in/out information.

Background

Geopositioning uses various visual and electronic methods including position lines and position circles, celestial navigation, radio navigation, radio and WiFi positioning systems, and the use of satellite navigation systems.

The calculation requires measurements or observations of distances or angles to reference points whose positions are known. In 2D surveys, observations of three reference points are enough to compute a position in a two-dimensional plane. In practice, observations are subject to errors resulting from various physical and atmospheric factors that influence the measurement of distances and angles. [4]

A practical example of obtaining a position fix would be for a ship to take bearing measurements on three lighthouses positioned along the coast. These measurements could be made visually using a hand bearing compass, or in case of poor visibility, electronically using radar or radio direction finding. Since all physical observations are subject to errors, the resulting position fix is also subject to inaccuracy. Although in theory two lines of position (LOP) are enough to define a point, in practice 'crossing' more LOPs provides greater accuracy and confidence, especially if the lines cross at a good angle to each other. Three LOPs are considered the minimum for a practical navigational fix. [5] The three LOPs when drawn on the chart will in general form a triangle, known as a 'cocked hat'. The navigator will have more confidence in a position fix that is formed by a small cocked hat with angles close to those of an equilateral triangle. [6] The area of doubt surrounding a position fix is called an error ellipse. To minimize the error, electronic navigation systems generally use more than three reference points to compute a position fix to increase the data redundancy. As more redundant reference points are added, the position fix becomes more accurate and the area of the resulting error ellipse decreases. [7]

The process of using 3 reference points to calculate the location is called Trilateration, and when using more than 3 points, multilateration.

Combining multiple observations to compute a position fix is equivalent to solving a system of linear equations. Navigation systems use regression algorithms such as least squares in order to compute a position fix in 3D space. This is most commonly done by combining distance measurements to 4 or more GPS satellites, which orbit the Earth along known paths. [8]

Visual fix by three bearings plotted on a nautical chart Visual-fix-by-three-bearings.png
Visual fix by three bearings plotted on a nautical chart

The result of position fixing is called a position fix (PF), or simply a fix, a position derived from measuring in relation to external reference points. [9] In nautical navigation, the term is generally used with manual or visual techniques, such as the use of intersecting visual or radio position lines, rather than the use of more automated and accurate electronic methods like GPS; in aviation, use of electronic navigation aids is more common. A visual fix can be made by using any sighting device with a bearing indicator. Two or more objects of known position are sighted, and the bearings recorded. Bearing lines are then plotted on a chart through the locations of the sighted items. The intersection of these lines is the current position of the vessel.

Usually, a fix is where two or more position lines intersect at any given time. If three position lines can be obtained, the resulting "cocked hat", where the three lines do not intersect at the same point, but create a triangle, gives the navigator an indication of the accuracy. The most accurate fixes occur when the position lines are perpendicular to each other. Fixes are a necessary aspect of navigation by dead reckoning, which relies on estimates of speed and course. The fix confirms the actual position during a journey. A fix can introduce inaccuracies if the reference point is not correctly identified or is inaccurately measured.

Indoor Geopositioning

Geopositioning can be referred to both global positioning and outdoor positioning, using for example GPS, and to indoor positioning, for all the situations where satellite GPS is not a viable option and the localization process has to happen indoors. For indoor positioning, tracking and localization there are many technologies that can be used, depending on the specific needs and on the environmental characteristics. [10]

See also

Related Research Articles

<span class="mw-page-title-main">Global Positioning System</span> American satellite-based radio navigation service

The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radio navigation system owned by the United States Space Force and operated by Mission Delta 31. It is one of the global navigation satellite systems (GNSS) that provide geolocation and time information to a GPS receiver anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. It does not require the user to transmit any data, and operates independently of any telephone or Internet reception, though these technologies can enhance the usefulness of the GPS positioning information. It provides critical positioning capabilities to military, civil, and commercial users around the world. Although the United States government created, controls, and maintains the GPS system, it is freely accessible to anyone with a GPS receiver.

<span class="mw-page-title-main">Geodesy</span> Science of measuring the shape, orientation, and gravity of Earth

Geodesy or geodetics is the science of measuring and representing the geometry, gravity, and spatial orientation of the Earth in temporally varying 3D. It is called planetary geodesy when studying other astronomical bodies, such as planets or circumplanetary systems. Geodesy is an earth science and many consider the study of Earth's shape and gravity to be central to that science. It is also a discipline of applied mathematics.

<span class="mw-page-title-main">Navigation</span> Process of monitoring and controlling the movement of a craft or vehicle from one place to another

Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another. The field of navigation includes four general categories: land navigation, marine navigation, aeronautic navigation, and space navigation.

<span class="mw-page-title-main">Surveying</span> Science of determining the positions of points and the distances and angles between them

Surveying or land surveying is the technique, profession, art, and science of determining the terrestrial two-dimensional or three-dimensional positions of points and the distances and angles between them. These points are usually on the surface of the Earth, and they are often used to establish maps and boundaries for ownership, locations, such as the designated positions of structural components for construction or the surface location of subsurface features, or other purposes required by government or civil law, such as property sales.

<span class="mw-page-title-main">Dead reckoning</span> Means of calculating position

In navigation, dead reckoning is the process of calculating the current position of a moving object by using a previously determined position, or fix, and incorporating estimates of speed, heading, and elapsed time. The corresponding term in biology, to describe the processes by which animals update their estimates of position or heading, is path integration.

<span class="mw-page-title-main">Celestial navigation</span> Navigation using astronomical objects to determine position

Celestial navigation, also known as astronavigation, is the practice of position fixing using stars and other celestial bodies that enables a navigator to accurately determine their actual current physical position in space or on the surface of the Earth without relying solely on estimated positional calculations, commonly known as dead reckoning. Celestial navigation is performed without using satellite navigation or other similar modern electronic or digital positioning means.

<span class="mw-page-title-main">Waypoint</span> Point on a route of travel

A waypoint is a point or place on a route or line of travel, a stopping point, an intermediate point, or point at which course is changed, the first use of the term tracing to 1880. In modern terms, it most often refers to coordinates which specify one's position on the globe at the end of each "leg" (stage) of an air flight or sea passage, the generation and checking of which are generally done computationally.

Piloting or pilotage is the process of navigating on water or in the air using fixed points of reference on the sea or on land, usually with reference to a nautical chart or aeronautical chart to obtain a fix of the position of the vessel or aircraft with respect to a desired course or location. Horizontal fixes of position from known reference points may be obtained by sight or by radar. Vertical position may be obtained by depth sounder to determine depth of the water body below a vessel or by altimeter to determine an aircraft's altitude, from which its distance above the ground can be deduced. Piloting a vessel is usually practiced close to shore or on inland waterways. Pilotage of an aircraft is practiced under visual meteorological conditions for flight.

<span class="mw-page-title-main">Wide Area Augmentation System</span> System that enhances the accuracy of GPS receivers

The Wide Area Augmentation System (WAAS) is an air navigation aid developed by the Federal Aviation Administration to augment the Global Positioning System (GPS), with the goal of improving its accuracy, integrity, and availability. Essentially, WAAS is intended to enable aircraft to rely on GPS for all phases of flight, including precision approaches to any airport within its coverage area. It may be further enhanced with the Local Area Augmentation System (LAAS) also known by the preferred ICAO term Ground-Based Augmentation System (GBAS) in critical areas.

<span class="mw-page-title-main">Satellite geodesy</span> Measurement of the Earth using satellites

Satellite geodesy is geodesy by means of artificial satellites—the measurement of the form and dimensions of Earth, the location of objects on its surface and the figure of the Earth's gravity field by means of artificial satellite techniques. It belongs to the broader field of space geodesy. Traditional astronomical geodesy is not commonly considered a part of satellite geodesy, although there is considerable overlap between the techniques.

<span class="mw-page-title-main">Satellite navigation</span> Use of satellite signals for geo-spatial positioning

A satellite navigation or satnav system is a system that uses satellites to provide autonomous geopositioning. A satellite navigation system with global coverage is termed global navigation satellite system (GNSS). As of 2024, four global systems are operational: the United States's Global Positioning System (GPS), Russia's Global Navigation Satellite System (GLONASS), China's BeiDou Navigation Satellite System (BDS), and the European Union's Galileo.

<span class="mw-page-title-main">Mobile phone tracking</span> Identifying the location of a mobile phone

Mobile phone tracking is a process for identifying the location of a mobile phone, whether stationary or moving. Localization may be affected by a number of technologies, such as the multilateration of radio signals between (several) cell towers of the network and the phone or by simply using GNSS. To locate a mobile phone using multilateration of mobile radio signals, the phone must emit at least the idle signal to contact nearby antenna towers and does not require an active call. The Global System for Mobile Communications (GSM) is based on the phone's signal strength to nearby antenna masts.

In astronomical navigation, the intercept method, also known as Marcq St. Hilaire method, is a method of calculating an observer's position on Earth (geopositioning). It was originally called the azimuth intercept method because the process involves drawing a line which intercepts the azimuth line. This name was shortened to intercept method and the intercept distance was shortened to 'intercept'.

Pseudo-range multilateration, often simply multilateration (MLAT) when in context, is a technique for determining the position of an unknown point, such as a vehicle, based on measurement of biased times of flight (TOFs) of energy waves traveling between the vehicle and multiple stations at known locations. TOFs are biased by synchronization errors in the difference between times of arrival (TOA) and times of transmission (TOT): TOF=TOA-TOT. Pseudo-ranges (PRs) are TOFs multiplied by the wave propagation speed: PR=TOF ⋅ s. In general, the stations' clocks are assumed synchronized but the vehicle's clock is desynchronized.

A positioning system is a system for determining the position of an object in space. Positioning system technologies exist ranging from interplanetary coverage with meter accuracy to workspace and laboratory coverage with sub-millimeter accuracy. A major subclass is made of geopositioning systems, used for determining an object's position with respect to Earth, i.e., its geographical position; one of the most well-known and commonly used geopositioning systems is the Global Positioning System (GPS) and similar global navigation satellite systems (GNSS).

Augmentation of a global navigation satellite system (GNSS) is a method of improving the navigation system's attributes, such as precision, reliability, and availability, through the integration of external information into the calculation process. There are many such systems in place, and they are generally named or described based on how the GNSS sensor receives the external information. Some systems transmit additional information about sources of error, others provide direct measurements of how much the signal was off in the past, while a third group provides additional vehicle information to be integrated in the calculation process.

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.

<span class="mw-page-title-main">Indoor positioning system</span> Network of devices used to wirelessly locate objects inside a building

An indoor positioning system (IPS) is a network of devices used to locate people or objects where GPS and other satellite technologies lack precision or fail entirely, such as inside multistory buildings, airports, alleys, parking garages, and underground locations.

Wi-Fi positioning system is a geolocation system that uses the characteristics of nearby Wi‑Fi access points to discover where a device is located.

Satellite geolocation is the process of locating the origin of a signal appearing on a satellite communication channel. Typically, this process is used to mitigate interference on communication satellites. Usually, these interference signals are caused by human error or equipment failure, but can also be caused by deliberate jamming. Identifying the geographical location of an interfering signal informs the mitigation activity.

References

  1. ↑ "geopositioning". ISO/TC 211 Geolexica. 2020-06-02. Retrieved 2020-08-31.
  2. ↑ Keating, J.B.; United States. Bureau of Land Management (1993). The Geo-Positioning Selection Guide for Resource Management. BLM technical note. Bureau of Land Management. p. 5. Retrieved 2020-08-31.
  3. ↑ "What is geofencing and how is it used? – TechTarget Definition". WhatIs. Retrieved 2024-09-10.
  4. ↑ B. Hofmann-Wellenhof; K. Legat; M. Wieser (28 June 2011). Navigation: Principles of Positioning and Guidance. Springer Science & Business Media. ISBN   978-3-7091-6078-7.
  5. ↑ Gentile, C.; Alsindi, N.; Raulefs, R.; Teolis, C. (2012). Geolocation Techniques: Principles and Applications. Springer New York. ISBN   978-1-4614-1836-8 . Retrieved 2020-08-31.
  6. ↑ Progri, I. (2011). Geolocation of RF Signals: Principles and Simulations. Springer New York. ISBN   978-1-4419-7952-0 . Retrieved 2020-08-31.
  7. ↑ Nait-Sidi-Moh, A.; Bakhouya, M.; Gaber, J.; Wack, M. (2013). Geopositioning and Mobility. ISTE. Wiley. p. 71. ISBN   978-1-118-74368-3 . Retrieved 2020-08-31.
  8. ↑ Laurie Tetley; David Calcutt (7 June 2007). Electronic Navigation Systems. Routledge. pp. 9–. ISBN   978-1-136-40725-3.
  9. ↑ Zamir, A.R.; Hakeem, A.; Van Gool, L.; Shah, M.; Szeliski, R. (2016). Large-Scale Visual Geo-Localization. Advances in Computer Vision and Pattern Recognition (in Romanian). Springer International Publishing. ISBN   978-3-319-25781-5 . Retrieved 2020-08-31.
  10. ↑ Brena, Ramon F.; García-Vázquez, Juan Pablo; Galván-Tejada, Carlos E.; Muñoz-Rodriguez, David; Vargas-Rosales, Cesar; Fangmeyer, James (2017). "Evolution of Indoor Positioning Technologies: A Survey". Journal of Sensors. 2017: 1–21. doi: 10.1155/2017/2630413 . hdl: 11285/630311 . ISSN   1687-725X.

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