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Radiolocation
Radiolocation
Radiolocation
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Radiolocation, also known as radiolocating or radiopositioning, is the process of finding the location of something through the use of radio waves. It generally refers to passive, particularly radar—as well as detecting buried cables, water mains, and other public utilities. It is similar to radionavigation in which one actively seeks its own position; both are types of radiodetermination. Radiolocation is also used in real-time locating systems (RTLS) for tracking valuable assets.

Basic principles

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An object can be located by measuring the characteristics of received radio waves. The radio waves may be transmitted by the object to be located, or they may be backscattered waves (as in radar or passive RFID). A stud finder uses radiolocation when it uses radio waves rather than ultrasound.

One technique measures a distance by using the difference in the power of the received signal strength (RSSI) as compared to the originating signal strength. Another technique uses the time of arrival (TOA), when the time of transmission and speed of propagation are known. Combining TOA data from several receivers at different known locations (time difference of arrival, TDOA) can provide an estimate of position even in the absence of knowledge of the time of transmission. The angle of arrival (AOA) at a receiving station can be determined by the use of a directional antenna, or by differential time of arrival at an array of antennas with known location. AOA information may be combined with distance estimates from the techniques previously described to establish the location of a transmitter or backscatterer. Alternatively, the AOA at two receiving stations of known location establishes the position of the transmitter. The use of multiple receivers to locate a transmitter is known as multilateration.

Estimates are improved when the transmission characteristics of the medium is factored into the calculations. For RSSI this means electromagnetic permeability; for TOA it may mean non-line-of-sight receptions.

Use of RSSI to locate a transmitter from a single receiver requires that both the transmitted (or backscattered) power from the object to be located are known, and that the propagation characteristics of the intervening region are known. In empty space, signal strength decreases as the inverse square of the distance for distances large compared to a wavelength and compared to the object to be located, but in most real environments, a number of impairments can occur: absorption, refraction, shadowing, and reflection. Absorption is negligible for radio propagation in air at frequencies less than about 10 GHz, but becomes important at multi-GHz frequencies where rotational molecular states can be excited. Refraction is important at long ranges (tens to hundreds of kilometers) due to gradients in moisture content and temperature in the atmosphere. In urban, mountainous, or indoor environments, obstruction by intervening obstacles and reflection from nearby surfaces are very common, and contribute to multipath distortion: that is, reflected and delayed replicates of the transmitted signal are combined at the receiver. Signals from different paths can add constructively or destructively: such variations in amplitude are known as fading. The dependence of signal strength on position of transmitter and receiver becomes complex and often non-monotonic, making single-receiver estimates of position inaccurate and unreliable. Multilateration using many receivers is often combined with calibration measurements ("fingerprinting") to improve accuracy.

TOA and AOA measurements are also subject to multipath errors, particularly when the direct path from the transmitter to receiver is blocked by an obstacle. Time of arrival measurements are also most accurate when the signal has distinct time-dependent features on the scale of interest—for example, when it is composed of short pulses of known duration—but Fourier transform theory shows that in order to change amplitude or phase on a short time scale, a signal must use a broad bandwidth. For example, to create a pulse of about 1 ns duration, roughly sufficient to identify location to within 0.3 m (1 foot), a bandwidth of roughly 1 GHz is required. In many regions of the radio spectrum, emission over such a broad bandwidth is not allowed by the relevant regulatory authorities, in order to avoid interference with other narrowband users of the spectrum. In the United States, unlicensed transmission is allowed in several bands, such as the 902-928 MHz and 2.4-2.483 GHz Industrial, Scientific, and Medical ISM bands, but high-power transmission cannot extend outside of these bands. However, several jurisdictions now allow ultrawideband transmission over GHz or multi-GHz bandwidths, with constraints on transmitted power to minimize interference with other spectrum users. UWB pulses can be very narrow in time, and often provide accurate estimates of TOA in urban or indoor environments.

Radiolocation is employed in a wide variety of industrial and military activities. Radar systems often use a combination of TOA and AOA to determine a backscattering object's position using a single receiver. In Doppler radar, the Doppler shift is also taken into account, determining velocity rather than location (though it helps determine future location). Real Time Location Systems RTLS using calibrated RTLS, and TDOA, are commercially available. The widely used Global Positioning System (GPS) is based on TOA of signals from satellites at known positions.

Mobile phones

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Main article: Mobile phone tracking

Radiolocation is also used in cellular telephony via base stations. Most often, this is done through trilateration between radio towers. The location of the Caller or handset can be determined several ways:

  • angle of arrival (AOA) requires at least two towers, locating the caller at the point where the lines along the angles from each tower intersect
  • time difference of arrival (TDOA) resp. time of arrival (TOA) works using multilateration, except that it is the networks that determine the time difference and therefore distance from each tower (as with seismometers)
  • location signature uses "fingerprinting" to store and recall patterns (such as multipath) which mobile phone signals are known to exhibit at different locations in each cell

The first two depend on a line-of-sight, which can be difficult or impossible in mountainous terrain or around skyscrapers. Location signatures actually work better in these conditions however. TDMA and GSM networks such as Cingular and T-Mobile use TDOA.

CDMA networks such as Verizon Wireless and Sprint PCS tend to use handset-based radiolocation technologies, which are technically more similar to radionavigation. GPS is one of those technologies.

Composite solutions, needing both the handset and the network include:

Initially, the purpose of any of these in mobile phones is so that the public safety answering point (PSAP) which answers calls to an emergency telephone number can know where the caller is and exactly where to send emergency services. This ability is known within the NANP (North America) as wireless enhanced 911. Mobile phone users may have the option to permit the location information gathered to be sent to other phone numbers or data networks, so that it can help people who are simply lost or want other location-based services. By default, this selection is usually turned off, to protect privacy.

International regulation

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Remote Radar Post 358 (RRP 117 of the German Air Force)

Radiolocation service (short: RLS) is – according to Article 1.48 of the International Telecommunication Union's (ITU) Radio Regulations (RR)[1] – defined as "A radiodetermination service for the purpose of radiolocation", where radiolocation is defined as: "radiodetermination used for purposes other than those of radionavigation."

Classification

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This radiocommunication service is classified in accordance with ITU Radio Regulations (article 1) as follows:
Radiodetermination service (article 1.40)

The radiolocation service distinguishes basically

Examples

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Satellites

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SAR-Lupe (space radio station of the radiolocation-satellite service)

Radiolocation-satellite service (short: RLSS) is – according to Article 1.49 of the International Telecommunication Union's (ITU) Radio Regulations (RR)[2] – defined as «A radiodetermination-satellite service used for the purpose of radiolocation. This (radiocommunication) service may also include the feeder links necessary for its operation.»

The radiolocation-satellite service distinguishes basically

  • Earth radio stations
  • Feeder links and
  • Space radio stations

For example military radar sensors in earth satellites operate in the radiolocation-satellite service n this service.

Examples of radio stations in the radiolocation-satellite service
List of radar-satellites (not complete)
Name Country Sensoric
Lacrosse USA military radar (imaging) reconnaissance satellite
SAR-Lupe Germany military radar (imaging) reconnaissance satellite
IGS Japan radar reconnaissance and optoelectronic reconnaissance
RORSAT Russian Federation Radar Ocean Reconnaissance SATellite

Frequency allocation

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The allocation of radio frequencies is provided according to Article 5 of the ITU Radio Regulations (edition 2012).[3]

In order to improve harmonisation in spectrum utilisation, the majority of service-allocations stipulated in this document were incorporated in national Tables of Frequency Allocations and Utilisations which is within the responsibility of the appropriate national administration. The allocation might be primary, secondary, exclusive, and shared.

Example of frequency allocation
Allocation to services
     Region 1           Region 2           Region 3     
24.65-24.75 GHz
FIXED
FIXED-SATELLITE
(Earth-to-space)
INTER-SATELLITE
 24.65-24.75
INTER-SATELLITE
RADIOLOCATION-SATELLITE
(Earth-to-space)
 24.65-24.75
FIXED
FIXED-SATELLITE
(Earth-to-space)
INTER-SATELLITE
MOBILE

Stations

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Land station

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RAdio Detection And Ranging
Principle

A radiolocation land station is – according to article 1.90 of the International Telecommunication Union's (ITU) ITU Radio Regulations (RR)[4] – defined as "a radio station in radiolocation service not intended to be used while in motion." Each radiolocation station shall be classified by the radiocommunication service in which it operates permanently or temporarily.

In accordance with ITU Radio Regulations (article 1) this type of radio station might be classified as follows:
Radiodetermination station (article 1.86) of the radiodetermination service (article 1.40 )

Selection radiolocation land stations
  • German Radar Wurzburg Riese (FuMG 65)
    German Radar Wurzburg Riese (FuMG 65)
  • ALTAIR (ARPA Long-Range Tracking and Instrumentation Radar)
    ALTAIR (ARPA Long-Range Tracking and Instrumentation Radar)
  • NASA Wallops Flight Facility Radar
    NASA Wallops Flight Facility Radar
  • Antenna radar L band TAR Finland
    Antenna radar L band TAR Finland
  • 50 Feet dish Antenna of a 3 kW C band Radar
    50 Feet dish Antenna of a 3 kW C band Radar
  • Intelligence-gathering phased array radar FPS-108 COBRA DANE
    Intelligence-gathering phased array radar FPS-108 COBRA DANE
  • Phased array radar AN/FPQ-16 PARCS
    Phased array radar AN/FPQ-16 PARCS
  • Skyguide radar, Hochwacht in Boppelsen on Lägern (Switzerland)
    Skyguide radar, Hochwacht in Boppelsen on Lägern (Switzerland)

Mobile station

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Radiolocation mobile station is – according to article 1.89 of the International Telecommunication Union's (ITU) ITU Radio Regulations (RR)[5] – defined as "A radio station in radiolocation service intended to be used while in motion or during halts at unspecified points." Each radiolocation station shall be classified by the radiocommunication service in which it operates permanently or temporarily.

In accordance with ITU Radio Regulations (article 1) this type of radio station might be classified as follows:
Radiodetermination station (article 1.86) of the radiodetermination service (article 1.40 )

Selection radiolocation mobile stations
  • Air Surveillance Radars TRML-3D
    Air Surveillance Radars TRML-3D
  • High finder radar
    High finder radar
  • RAAF radar, AN/TPS-77
    RAAF radar, AN/TPS-77
  • German radar sensor LÜR
    German radar sensor LÜR
  • MIM-104 Patriot in Japanese service
    MIM-104 Patriot in Japanese service
  • Nike Hercules IFC radars LOPAR and the tracking radars (MTR, TTR, TRR) f.l.t.r.
    Nike Hercules IFC radars LOPAR and the tracking radars (MTR, TTR, TRR) f.l.t.r.
  • APAR-radar Fregatte Hamburg (F 220)
    APAR-radar Fregatte Hamburg (F 220)
  • Weapon control radar
    Weapon control radar
  • Sea-based x-band radar underway
    Sea-based x-band radar underway
  • Air borne radar „Lichtenstein SN-2“ in the ME Bf 110G
    Air borne radar „Lichtenstein SN-2“ in the ME Bf 110G

See also

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References

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Further reading

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

Radiolocation

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from Grokipedia
Radiolocation is a form of radiodetermination that involves the determination of the position, , and/or other characteristics of an object, or the obtaining of information relating to these parameters, by means of the propagation properties of radio waves, specifically for purposes other than . The radiolocation service, as defined internationally, encompasses radiodetermination systems dedicated to these non-navigational objectives, distinguishing it from radionavigation services used for guiding or vessels. This technology relies on the transmission and reception of signals, typically below 3000 GHz, to detect and locate distant objects through reflection, absorption, or directional properties of electromagnetic waves. The fundamental principles of radiolocation are rooted in the physics of radio wave propagation, where transmitters emit signals that interact with targets, allowing receivers to measure parameters such as time-of-flight for distance, phase differences for direction, or Doppler shifts for velocity. Early methods include , which exploits the directional sensitivity of antennas to estimate bearing, a technique pioneered through experiments demonstrating reflection off metallic objects. More advanced systems, such as pulse radar, transmit short bursts of and analyze echoes to compute range and position, while modern variants like (SAR) enhance resolution by simulating larger antennas through motion. These principles enable operation in diverse environments, including those affected by weather, by employing techniques like to mitigate interference from or . The development of radiolocation traces back to the late , when Heinrich Hertz's 1888 experiments confirmed the reflection of radio waves by metallic surfaces, laying the groundwork for directional detection. In 1904, Christian Hülsmeyer patented the first practical device, the Telemobiloskop, an early -like system for detecting ships in fog, marking the initial application of radiolocation for collision avoidance. Significant advancements occurred during , when nations independently developed technologies for military surveillance and targeting, transforming radiolocation from experimental curiosity to essential defense tool. Post-war, the field expanded with international standardization efforts, including the establishment of frequency allocations by the (ITU) to prevent interference among global systems. Contemporary radiolocation applications span surveillance, tracking, and scientific measurement, including air traffic monitoring, maritime vessel detection, operations, and oceanographic radar for current mapping, all conducted without direct navigational intent. In , it supports launch tracking and orbital monitoring, while industrial uses involve locating vehicles or personnel in and . Recent developments as of 2025 include new allocations for non-Federal operations in the 2025-2110 MHz band and proposals for ground-based radiolocation in 24.45-24.65 GHz to support advanced air mobility. Governed by , the service operates in allocated frequency bands to ensure compatibility with other radiocommunication services, with ongoing updates addressing emerging needs like millimeter-wave for . These applications underscore radiolocation's role in enhancing and across civilian and military domains.

Fundamentals

Definition and Basic Principles

Radiolocation is defined as a radiodetermination service for the purpose of determining the position, velocity, and/or other characteristics of objects, or obtaining related information, by means of the propagation properties of radio waves, excluding applications intended to the movement of vehicles such as , ships, or ground vehicles, which fall under radionavigation. This service encompasses both active systems that emit radio signals and passive systems that rely on existing emissions, enabling the detection and localization of targets through signal interactions. At its core, radiolocation relies on the fundamental physics of electromagnetic radio waves, which propagate through free space at the , approximately c=3×108c = 3 \times 10^8 m/s. These waves interact with objects via reflection, where they bounce off surfaces altering direction; absorption, in which energy is dissipated into the medium; and , allowing waves to bend around obstacles, facilitating signal detection beyond direct line-of-sight paths. Such interactions form the basis for inferring object positions by analyzing time delays, phase shifts, or signal strengths. Key challenges in radiolocation stem from environmental and propagation effects that degrade signal accuracy. occurs when signals arrive via multiple reflected paths, creating echoes that interfere constructively or destructively and cause . Non-line-of-sight (NLOS) conditions, arising from obstacles like buildings or , block direct signals and force reliance on weaker diffracted or scattered paths, reducing precision. Additionally, atmospheric factors such as rain, fog, or ionospheric variations can attenuate signals or introduce scintillation, further impacting reliability in diverse operational scenarios. Radiolocation overlaps with radar systems, which typically employ active emission of radio waves to detect reflections from targets, whereas passive radiolocation utilizes ambient radio signals from external sources without dedicated transmission, offering stealth advantages but limited control over illumination.

Historical Development

The foundations of radiolocation trace back to the late , when Heinrich Hertz's experiments in 1888 demonstrated the directional properties of electromagnetic waves, laying the groundwork for (RDF) by showing how radio waves could be transmitted and received in specific directions using simple loop antennas. These discoveries built on James Clerk Maxwell's theoretical predictions of electromagnetic , enabling early practical applications in locating radio sources. In the , advanced systems that incorporated rudimentary direction-finding techniques, allowing operators to determine the bearing of transmitted signals over distances, which proved essential for maritime communication and . Around the same time, proposed in 1900 the use of radio waves to detect distant objects, such as ships, by measuring echoes—a concept that foreshadowed technology, though it remained theoretical at the stage. During in the 1910s, RDF evolved rapidly for , with systems deployed on ships to locate enemy vessels by triangulating signals from wireless transmitters, marking the first widespread military application of radiolocation for tactical advantage. This momentum continued into the 1930s, as spurred major innovations: the United Kingdom's radar network, developed under , became operational in 1937 and provided early warning of incursions by detecting echoes from radio pulses at ranges up to 150 miles. Similarly, the introduced the mobile radar in 1938, capable of spotting at 150 miles, which exemplified radiolocation's shift toward active detection systems and underscored its critical role in air defense during the war. Post-World War II, radiolocation expanded into civilian domains with the (ITU) formalizing regulations in its 1947 Atlantic City Radio Regulations, which defined the radiolocation service as involving the use of radio waves to determine the position or direction of objects, with the radionavigation service as a specific application thereof for aiding the movement of ships, vehicles, or .

Techniques and Methods

Time-Based Methods

Time-based methods in radiolocation determine the position, , or other characteristics of an object (which may be a transmitter, receiver, or passive reflector) by measuring the time of radio signals, leveraging the constant in free to convert time into . These techniques form the foundation of many positioning systems, where the core is that the dd between a transmitter and receiver is given by d=c×td = c \times t, with cc as the (approximately 3×1083 \times 10^8 m/s) and tt as the signal time. Accurate between clocks at the transmitter and receiver is essential for these methods, as even nanosecond-scale errors can translate to meter-level positioning inaccuracies. The time of arrival (TOA) method measures the absolute time elapsed from signal transmission to reception, enabling direct estimation when clocks are precisely . In practice, TOA systems often employ pseudoranges, which account for unknown clock biases between the transmitter and receiver, allowing position calculation via multilateration from multiple points. A prominent example is pulse radar systems used in , where short bursts of radio waves are transmitted, and the round-trip time of echoes from targets is measured to compute range and position, with the radar's co-located transmitter and receiver providing inherent synchronization. This approach achieves positioning accuracies on the order of meters, though it requires consideration of to minimize multipath errors. In contrast, the time difference of arrival (TDOA) method avoids the need for absolute time synchronization by measuring the difference in arrival times of a signal at multiple receivers, each pair defining a on which the transmitter must lie. The position is then estimated as the intersection point of these hyperbolas from several receiver pairs, typically solved using nonlinear optimization techniques such as to minimize errors due to noise and propagation delays. The TDOA position can be formulated as minimizing the sum of squared residuals: min⁡∑i(Δti−di−d\refc)2\min \sum_i \left( \Delta t_i - \frac{d_i - d_{\ref}}{c} \right)^2 where Δti\Delta t_i is the measured time difference for receiver pair ii, did_i is the distance from the transmitter to receiver ii, d\refd_{\ref} is the distance to a reference receiver, and cc is the speed of light; this weighted least squares approach enhances robustness in noisy environments. In cellular networks, TDOA implementations achieve accuracies of 10-100 meters, depending on base station geometry and signal bandwidth. Passive TDOA systems are also used in radiolocation for geolocating radio frequency emitters in surveillance applications, such as electronic intelligence gathering. Implementation challenges in both TOA and TDOA primarily stem from clock synchronization errors, which can introduce biases exceeding the signal propagation time and degrade positioning precision. These errors are commonly mitigated through GPS-assisted timing, where global navigation satellite system receivers provide a common time reference to synchronize local clocks, often augmented by high-stability oscillators like oven-controlled crystal oscillators (OCXOs) for sub-microsecond accuracy. In modern contexts, (UWB) technology applies TOA for high-precision indoor positioning, exploiting short nanosecond pulses across a wide bandwidth (over 500 MHz) to resolve multipath and achieve centimeter-level accuracy in environments like buildings or warehouses. UWB systems, standardized under , demonstrate positioning errors below 10 cm in line-of-sight indoor tests, making them suitable for and .

Angle-Based Methods

Angle-based methods in radiolocation determine the position of an object by measuring the direction, or bearing, from which radio signals arrive or are reflected, typically using the principles of directional antennas or antenna arrays. These techniques rely on the angular of the signal to compute bearings, which can then be triangulated from multiple stations to locate the source. Unlike time-based approaches, angle-based methods focus on the geometric direction rather than propagation delays, making them suitable for scenarios where precise is needed, such as and object tracking. A primary angle-based technique is Angle of Arrival (AOA), which employs directional antennas or phased antenna arrays to estimate the incidence angle of an incoming signal. In AOA systems, the bearing angle θ\theta is derived from phase differences Δϕ\Delta\phi across array elements spaced by distance dd, using the formula θ=arcsin⁡(λΔϕ2πd),\theta = \arcsin\left(\frac{\lambda \Delta \phi}{2\pi d}\right), where λ\lambda is the signal wavelength; this phase shift arises because the wavefront reaches each element at slightly different times. Antenna arrays enable electronic beam steering to achieve high angular resolution, often better than 1 degree in modern implementations. Radio Direction Finding (RDF) is a foundational angle-based method that uses to identify signal bearings by exploiting the antenna's directional response. A produces a null—a sharp minimum in received signal strength—when oriented perpendicular (90 degrees) to the direction of the incoming signal, as it responds primarily to the magnetic component of the electromagnetic wave orthogonal to the loop plane. Traditional RDF systems rotate the loop to find this null for bearing determination, though this introduces a 180-degree since the pattern is bidirectional. Modern RDF employs antennas for full 360-degree coverage without mechanical rotation, achieving accuracies below 1 degree through correlative . The Watson-Watt technique enhances RDF by addressing ambiguities in bearing estimation through amplitude comparison using orthogonal antenna pairs. It deploys two pairs of Adcock antennas—one aligned north-south and the other east-west—to capture signal components in directions, then compares their relative signal strengths to compute the angle of arrival. This method integrates with goniometers to resolve the 180-degree ambiguity inherent in single-loop systems by analyzing phase and amplitude ratios, forming cardioid patterns for unambiguous direction indication. Developed in the for location, it remains influential in due to its simplicity and robustness. Despite their effectiveness, angle-based methods face limitations such as 180-degree bearing ambiguities and susceptibility to , where reflected signals distort the apparent . These ambiguities are often resolved using dual RDF stations for or sense antennas to compare signal phases. A representative example is the use of RDF in maritime radiolocation for detecting and locating vessels through their transmissions, providing bearing information for collision avoidance and search operations with accuracies generally better than 2 degrees.

Hybrid and Advanced Techniques

Multilateration techniques integrate time difference of arrival (TDOA) measurements from at least three receivers with angle of arrival (AOA) data to enable two-dimensional (2D) or three-dimensional (3D) positioning of an object. This hybrid approach addresses limitations of standalone methods by combining hyperbolic positioning from TDOA with directional information from AOA, solving nonlinear equations through iterative trilateration algorithms that estimate the position (x,y)(x, y) while minimizing geometric dilution of precision (GDOP), a metric quantifying error amplification due to receiver geometry. In practical implementations, such as wide-area multilateration systems for aircraft surveillance, fusion of TDOA and AOA achieves sub-meter accuracy in outdoor environments by reducing ambiguity in position solutions. Received signal strength indication (RSSI) provides a complementary hybrid method by estimating from signal power attenuation, particularly useful in scenarios where time or angle measurements are unreliable. The core model follows the log- : Pr=Pt−10nlog⁡10(d)−XP_r = P_t - 10n \log_{10}(d) - X where PrP_r is the received power, PtP_t is the transmit power, nn is the exponent (typically 2–4 depending on the environment), dd is the , and XX represents shadowing losses. For indoor applications, RSSI often employs fingerprinting, where pre-collected signal strength databases at known locations are matched against real-time measurements to resolve positions, improving accuracy in multipath-heavy settings over pure modeling. Advanced integrations enhance hybrid techniques through and computational methods for real-time performance. Kalman filtering merges time-of-arrival (TOA), AOA, and RSSI inputs by recursively estimating position states, accounting for noise and dynamics to achieve robust tracking with errors reduced to tens of centimeters in indoor (BLE) systems. In networks, algorithms mitigate non-line-of-sight (NLOS) errors—common in urban deployments—by predicting propagation corrections from historical data, with post-2020 approaches like online learning frameworks yielding up to 50% accuracy gains in ranging estimates. Emerging hybrid technologies leverage (UWB) signals combined with TDOA or AOA for centimeter-level precision in (IoT) applications, such as asset tracking, where UWB's high time resolution enables distances accurate to 10 cm even in cluttered spaces. Looking toward 2025 trends, systems incorporate with integrated sensing and communication (ISAC) for hybrid positioning in ultra-dense environments, using AI-optimized beams to fuse multi-antenna angle data with time measurements, supporting sub-meter localization amid high mobility and interference.

Regulatory Framework

International Regulations

The (ITU) , in their 2024 edition, serve as the primary international governing the use of radio frequencies, including those for radiolocation services, and are adopted through periodic World Radiocommunication Conferences (WRC). Article 1 of the Regulations defines radiodetermination services, which encompass radiolocation as the determination of an object's position or other characteristics by means other than radionavigation using radio wave propagation properties, thereby establishing a framework for interference-free spectrum utilization across member states. Key provisions in the Regulations include protections against harmful interference under Article 15, which prohibits emissions that endanger safety services or seriously degrade radiocommunication, requiring administrations to cooperate in detection, elimination, and resolution through technical measures and goodwill. Coordination procedures for cross-border operations are outlined in Article 9, mandating notifications, agreements, and technical analyses (e.g., No. 9.21) to prevent interference for services like radiolocation, particularly in shared or adjacent bands. The outcomes of WRC-23 in 2023 further enhanced allocations by identifying additional spectrum for International Mobile Telecommunications (IMT), including systems, with specific conditions such as power flux-density limits to protect existing radiolocation services in bands such as the upper 6 GHz band (6.425-7.125 MHz). Enforcement of these Regulations occurs at the national level, where administrations issue licenses and monitor compliance to align with ITU provisions; for instance, the U.S. (FCC) incorporates ITU allocations into its Table of Frequency Allocations, ensuring radiolocation operations in designated bands adhere to international coordination requirements. The regulatory framework evolved following the ITU's post-World War II restructuring, with the initial Radio Regulations adopted at the 1947 International Telecommunication Conference in Atlantic City, establishing global principles. Subsequent updates occur through WRC cycles every three to four years; notably, WRC-19 initiated studies leading to mmWave band considerations (e.g., 231.5-275 GHz) for high-resolution radiolocation sensing, promoting compatibility with emerging technologies while maintaining protections for primary services.

Service Classifications

The radiolocation service, as defined in Article 1.48 of the , is a radiodetermination service aimed at determining the position, , or other characteristics of an object, or obtaining related , through the use of radio waves, excluding purposes related to radionavigation. This service encompasses a broad range of applications focused on general location and tracking without the specific intent of facilitating movement or navigation. In distinction, the radionavigation service under Article 1.47 is a radiocommunication service intended for determining the position, velocity, or other characteristics of objects to aid in navigation, obstruction warning, or traffic control. Another related category is the radiodetermination-satellite service per Article 1.49, which employs one or more space stations for radiodetermination, including space-based radiolocation, and may incorporate necessary feeder links. Additionally, the exploration-satellite service (Article 1.50) utilizes radiolocation methods for probing the Earth's surface and atmosphere, often integrated with satellite operations. Within the radiolocation service, systems are categorized as active or passive based on operational mode. Active radiolocation involves stations that transmit radio signals to illuminate targets and receive echoes, as seen in applications for . Passive radiolocation, conversely, relies solely on receiving and processing signals emitted by the target or external sources, without transmission from the locating station, enabling stealthier or lower-power operations. Further classification distinguishes fixed radiolocation services, where stations remain at specified locations (per Article 1.84), from mobile radiolocation services, where stations are designed for movement, such as vehicle- or aircraft-mounted systems (per Article 1.85). Practical implementations include industrial uses, such as in environments to monitor equipment positions via short-range radio techniques. In the context, radiolocation is authorized in select bands on a secondary basis, subject to power restrictions like a maximum radiated power of 50 W in certain allocations to minimize interference.

Frequency Allocations

The (ITU) manages global spectrum through Article 5 of the Radio Regulations, which outlines the Table of Frequency Allocations specifying bands for various services, including radiolocation on a primary or secondary basis. Radiolocation allocations span from VHF to millimeter waves, with primary status in key bands to support and positioning systems while accommodating sharing with other services. In the lower microwave range, the 1-3 GHz spectrum includes several primary allocations for radiolocation, such as 1 215-1 300 MHz (co-primary with earth exploration-satellite active and radionavigation-satellite services, with footnote 5.329 requiring protection for aeronautical radionavigation) and 2 700-3 100 MHz (shared with aeronautical radionavigation and meteorological aids under footnotes 5.423 and 5.424). The 8-10 GHz range features extensive primary radiolocation allocations, including 8 025-8 400 MHz (with earth exploration-satellite active, footnote 5.462A), 8 500-9 200 MHz (shared with radionavigation and limited to specific radar types like airborne Doppler aids under footnote 5.470), and 9 300-9 500 MHz (co-primary with earth exploration-satellite active and active). For automotive applications, the band 24.05-24.25 GHz is allocated primary to radiolocation worldwide, expanded post-WRC-19 to facilitate short-range sensors, with sharing alongside amateur services (footnote 5.532). Sharing rules are governed by footnotes in the ITU table, emphasizing co-primary status with fixed and mobile services in many bands to minimize interference; for instance, the 1 215-1 240 MHz band mandates protection for aeronautical radionavigation-satellite systems (footnotes 5.329A and 5.330). In millimeter-wave spectrum, the 57-71 GHz range supports primary radiolocation allocations, such as 57-58.2 GHz and 59-64 GHz (shared with fixed, mobile, and inter-satellite services under footnotes 5.547 and 5.559), enabling short-range high-resolution applications following WRC-23 additions. Global variations arise due to ITU's three regions: Region 1 (Europe, , ) often imposes stricter coordination for mobile sharing (e.g., 3 300-3 400 MHz includes fixed/mobile except aeronautical mobile, footnotes 5.429-5.429F), while Region 2 () features amateur service inclusions and U.S.-specific primaries (e.g., 420-450 MHz). Region 3 () aligns closely with Region 1 but varies in power limits, such as reduced emissions to protect adjacent services. Power limits, like those in footnote 5.475 for 9 300-9 500 MHz radars, ensure non-interference with radionavigation. Emerging trends include 2025 considerations for integrated sensing in 6G systems within existing 7-8 GHz radiolocation bands, such as secondary allocations in 6 700-7 075 MHz and primary in 8 025-8 400 MHz, to support submillimeter sensing without new spectrum reallocation.
Frequency Band (GHz)StatusKey Sharing ServicesRepresentative FootnoteRegional Notes
1.215-1.3PrimaryRadionavigation-satellite, Earth exploration-satellite (active)5.329 (aeronautical protection)Global, with Region 2 coordination
2.7-3.1PrimaryAeronautical radionavigation, Meteorological aids5.424 (no interference to nav)Region 2 equal for meteorological radars
8.025-8.4PrimaryEarth exploration-satellite (active)5.462A (sharing rules)Global
8.5-9.2PrimaryRadionavigation (airborne Doppler)5.470 (limited uses)Global
24.05-24.25PrimaryAmateur5.532 (post-WRC-19 expansion)Global
57-64PrimaryFixed, Mobile, Inter-satellite5.559 (airborne radars)Global, Region 1 coordination
64-66PrimaryInter-satellite, Mobile5.562 (restrictions)Region 2 primary

Applications

Mobile Communications

Radiolocation plays a critical role in mobile communications, particularly in cellular networks where precise positioning enhances emergency services, user tracking, and location-based applications. The U.S. (FCC) established the (E911) mandate in 1996, requiring wireless carriers to provide location information for emergency calls with Phase II accuracy standards of 50 meters for at least 67% of calls in urban areas. This initiative drove the adoption of Assisted GPS (A-GPS) in CDMA and networks, where cellular infrastructure delivers ephemeris data and timing assistance to mobile devices, reducing time-to-first-fix and improving horizontal accuracy to 5-10 meters under good signal conditions. A-GPS integrates with network elements to mitigate GPS limitations in urban canyons, enabling reliable positioning for handheld devices without solely relying on signals. Network-based radiolocation methods, such as Time Difference of Arrival (TDOA), further support cellular positioning in and systems by measuring signal arrival times at multiple base stations. For instance, uplink TDOA was implemented in networks like those of Cingular (now part of ) and , allowing location estimation without device modifications and achieving accuracies suitable for E911 compliance, typically in the range of 50-100 meters depending on cell density. In New Radio (NR), Observed TDOA (OTDOA) builds on this foundation with enhanced reference signals and multi-antenna arrays, enabling sub-meter horizontal accuracy—down to 1 meter in optimal scenarios—through higher bandwidth and beamforming. This precision supports advanced use cases like (V2X) communications while maintaining with legacy networks. Modern developments in mobile radiolocation increasingly incorporate hybrid approaches for challenging environments, such as and integration for indoor positioning in smartphones and tablets. These systems fuse received signal strength indicators (RSSI) with low-energy beacons to achieve accuracies of 2-5 meters indoors, complementing cellular methods by leveraging existing device hardware for seamless transitions between outdoor and indoor spaces. As of 2025, enhanced Mobile Broadband (eMBB) in networks enables real-time tracking for IoT devices, with high data rates and low latency supporting applications like and fleet monitoring through integrated positioning protocols. Practical examples illustrate these advancements in regulatory and commercial contexts. Apple's network utilizes crowdsourced signals from over one billion devices to locate lost items with privacy-preserving , achieving effective tracking even when the target device is offline. Similarly, the European Union's system, mandatory for new vehicles since 2018, automatically transmits vehicle location data via cellular networks during accidents to facilitate rapid response, ensuring compliance with 112-based services across member states. In 2025, EU regulations were updated to advance NG eCall compatibility with and networks, with mandatory implementation from 2026.

Satellite Systems

The radiolocation-satellite service, as defined by the (ITU), is a radiodetermination-satellite service utilizing Earth-orbiting satellites for the purpose of radiolocation, which may also incorporate feeder links necessary for its operation. This service enables global or wide-area positioning and tracking through space-based radio signals, distinct from terrestrial systems by providing coverage over remote and oceanic regions. Key implementations rely on time-of-arrival (TOA) pseudoranges for determining user positions relative to satellite constellations. Prominent examples include the (GPS), operated by the , which achieved full operational capability in 1995 with an initial constellation of 24 satellites and has since expanded to 32 operational satellites as of 2025. Russia's system, similarly structured with a nominal 24 satellites in , provides comparable global navigation and positioning services as a radionavigation-satellite service that supports radiolocation applications. The European Union's Galileo system, now fully operational with 31 satellites as of 2025 and initiated with in-orbit validation satellites launched starting in 2011, enhances these capabilities through features like the Open Service Navigation Message Authentication (OSNMA), which verifies signal integrity to prevent spoofing in radiolocation scenarios. Military applications of satellite radiolocation include Germany's SAR-Lupe constellation, a five-satellite synthetic aperture radar (SAR) system launched between 2006 and 2008 to provide all-weather imaging for reconnaissance and target location. The United States' Lacrosse/Onyx series, with launches spanning 1988 to 2005, utilized SAR technology aboard satellites in low Earth orbit for high-resolution radar imaging, including ocean surveillance to detect and locate maritime targets. Emerging developments as of 2025 involve low-Earth orbit (LEO) constellations like SpaceX's , which is expanding to offer auxiliary positioning services as an alternative to traditional GPS, enabling low-latency radiolocation through its growing network of over 8,800 satellites as of late 2025. These systems achieve global centimeter-level accuracy when augmented by (DGPS), which applies from reference stations to mitigate errors in pseudorange measurements. A primary challenge is ionospheric delays, which refract signals and introduce timing errors; these are corrected using dual-frequency observations on L1 (1575.42 MHz) and L2 (1227.60 MHz) bands to compute the ionosphere-free linear combination, reducing delays to negligible levels for precise radiolocation.

Radar and Sensing Systems

Radar systems represent a cornerstone of active radiolocation, employing transmitters to emit electromagnetic pulses that reflect off , enabling precise detection, ranging, and . Unlike passive methods that rely on ambient signals, active generates its own probing signals, typically in frequencies, to achieve high-resolution sensing in various environments. The fundamental operation involves measuring the time delay of the echo to determine range and the frequency shift to assess motion, making indispensable for , , and industrial monitoring. The range RR to a target is calculated from the round-trip propagation time τ\tau of the pulse, using the formula R=c×τ2R = \frac{c \times \tau}{2}, where cc is the in vacuum (approximately 3 × 10^8 m/s). This derives from the pulse traveling to the target and back, dividing the total distance by 2 to obtain the one-way range. Velocity estimation leverages the , where the shift Δf\Delta f in the returned signal indicates relative motion: v=Δf×c2f0v = \frac{\Delta f \times c}{2 f_0}, with f0f_0 as the transmitted ; the factor of 2 accounts for the round-trip path. These principles allow to resolve targets amid noise and multipath, though challenges like signal attenuation and clutter require advanced . Pulse-Doppler radar exemplifies these fundamentals by combining pulsed transmission for range resolution with Doppler filtering to distinguish moving targets from stationary clutter, enhancing detection in dynamic scenarios. A prominent example is the Airport Surveillance Radar Model 11 (ASR-11), deployed by the U.S. for terminal , operating in the S-band at 2.7–2.9 GHz to provide and tracking up to 60 nautical miles. This system uses staggered pulse repetition frequencies to mitigate range ambiguities, achieving azimuth accuracies of about 0.2 degrees while handling precipitation clutter through digital processing. Synthetic aperture radar (SAR) advances imaging capabilities by exploiting platform motion to synthesize a large virtual antenna, yielding high-resolution maps from airborne or spaceborne platforms. Launched in June 2007 by the (DLR), the satellite employs X-band (9.65 GHz) SAR to deliver resolutions down to 0.25 meters in spotlight mode, enabling detailed surface imaging for and disaster assessment independent of weather or daylight. Its active phased-array antenna supports multiple modes, including stripmap and scanSAR, processing echoes via range-Doppler algorithms to form two-dimensional images with sub-meter accuracy. In automotive applications, integrates into advanced driver-assistance systems (ADAS) for collision avoidance and , operating at 77 GHz to balance resolution and range in compact . Post-2020 developments have introduced 4D imaging , which extends traditional 2D range-Doppler maps to include , providing point clouds with under 1 degree for object in cluttered roads. For instance, Bosch's 2020 sixth-generation at 77 GHz achieves 300-meter detection range and supports level-3 by fusing with cameras and . These systems use frequency-modulated continuous-wave (FMCW) techniques to resolve velocities up to 300 km/h amid urban interference. Industrial real-time locating systems (RTLS) leverage principles, particularly (UWB) impulse , for precise in factories and warehouses, achieving centimeter-level accuracy without line-of-sight. UWB transmits short pulses across 3.1–10.6 GHz to measure time-of-flight for positioning tags on equipment or pallets, enabling real-time and optimization. Deployments in manufacturing, such as ' RTLS, integrate UWB anchors to track automated guided vehicles (AGVs) with latencies under 10 milliseconds, reducing search times by up to 50% in dynamic environments. As of 2025, quantum-enhanced emerges as a trend for detecting stealth targets, utilizing entangled photons to improve signal-to-noise ratios beyond classical limits, potentially identifying low-radar-cross-section objects like . Experimental advances, including quantum illumination prototypes, demonstrate enhanced sensitivity in noisy channels, with tests showing up to 6 dB gains in exponent for target . Concurrently, AI integration revolutionizes clutter rejection in urban sensing, where algorithms, such as convolutional neural networks, process returns to suppress multipath and non-stationary interference, improving target detection probabilities by 20–30% in dense scenarios. These AI-driven approaches, applied in integrated sensing and communication systems, adaptively filter urban clutter for applications like monitoring.

Infrastructure

Land Stations

Land stations in the radiolocation service are defined by the (ITU) as fixed stations located on land, utilizing radio waves to determine the position of objects or obtain related positional information, distinct from mobile or airborne variants. These stations serve critical roles in applications such as (RDF) towers and sites, providing stationary infrastructure for wide-area coverage in and search operations. Unlike portable units, they are designed for permanent installation to ensure reliable, high-power signal transmission and reception over extended ranges. Key components of land stations include high-power antennas and advanced systems. Antennas, often parabolic in design for implementations, typically achieve gains of 30-40 dBi to focus energy effectively, enabling detection at distances exceeding hundreds of kilometers. Signal processors handle analysis, error correction, and , enhancing accuracy in challenging environments. A representative example is the U.S. Coast Guard's (USCG) coastal RDF stations, which employ directional antennas to triangulate distress signals from vessels during maritime operations, covering sectors oriented seaward for optimal performance. Operations of land stations often involve fixed multilateration networks, where multiple synchronized transmitters enable position fixes through time-of-arrival measurements. High-frequency (HF) oceanographic radar networks exemplify this, using land-based stations operating in the 3-30 MHz band to map surface currents and waves over coastal areas up to 200 km offshore. Transmitter power in such networks typically ranges from 10 W to 100 W () to comply with ITU regulatory limits on interference while achieving the necessary signal strength for reliable coverage. These limits ensure equitable spectrum use, with maximum values set band-specifically to prevent harmful interference to adjacent services. Maintenance and upgrades for land stations emphasize reliability and modernization, incorporating (DSP) techniques to mitigate noise and multipath interference, thereby improving signal-to-noise ratios by up to 20 dB in operational environments. Many remote sites utilize fiber-optic backhaul for high-bandwidth data transfer to central control facilities, replacing legacy microwave links to support real-time monitoring and reduce latency in signal synchronization. This infrastructure evolution enhances overall system resilience against environmental factors and cyber threats.

Mobile Stations

Mobile stations in radiolocation refer to stations in the mobile service intended to be used while in motion or during halts at unspecified points, as defined in Article 1.67 of the ITU Radio Regulations. These encompass vehicle-mounted radar systems and handheld radio direction finders (RDF) that enable dynamic positioning and tracking in environments where fixed infrastructure is impractical. Such stations operate within the radiolocation service, which involves the determination of the position, velocity, or other characteristics of an object or obtaining information relating to these parameters by means of the propagation properties of radio waves. Design features of mobile stations prioritize portability and robustness for operation in transit. Compact antennas, such as omnidirectional designs, facilitate 360° angle-of-arrival (AOA) measurements essential for real-time in portable RDF units. These systems are typically battery-powered, with output powers ranging from 10-50 W to balance range and energy efficiency in mobile scenarios, as seen in vehicle-integrated transceivers. Integration with GPS receivers enhances self-positioning accuracy, allowing stations to compensate for their own motion and improve relative localization of targets. Representative examples include portable (UWB) locators used in search-and-rescue operations, such as the LifeLocator TRx system, which detects subtle movements like breathing through debris using low-power UWB pulses for non-invasive victim location. Another is drone-mounted for aerial surveying, exemplified by frequency-modulated continuous-wave (FMCW) systems operating in the 5-10 GHz bands to map terrain or detect objects from elevated, mobile platforms. Mobility introduces challenges like and Doppler effects, which distort and degrade accuracy in moving platforms. These are mitigated through inertial sensors, such as gyroscopes and accelerometers, that provide and stabilize returns in vehicle-mounted configurations. As of 2025, advancements in 5G-enabled mobile base stations support ad-hoc networks for enhanced radiolocation, enabling device-to-device positioning with sub-meter accuracy via sidelink communications and integrated sensing in dynamic environments.

Operational Examples

In maritime operations, the Automatic Identification System (AIS) exemplifies integrated radiolocation for vessel tracking, operating on VHF frequencies of 161.975 MHz (Channel 87B) and 162.025 MHz (Channel 88B). AIS transponders on ships broadcast identity, position, course, and speed data, while shore-based receivers employ Time Difference of Arrival (TDOA) techniques to multilaterate vessel positions with accuracies typically under 10 meters in coastal areas. This system became mandatory under the 2002 amendments for ships over 300 gross tons on international voyages, passenger ships, and certain cargo vessels, effective December 31, 2004, enhancing collision avoidance and search-and-rescue coordination globally. In , bird detection systems at utilize dedicated to monitor and track avian and drone activity around runways and , providing real-time alerts to prevent bird strikes and enhance safety. These systems, such as the MERLIN Avian Radar, operate in various frequency bands like X-band and achieve detection ranges up to 10 km with classification capabilities for different bird species. Deployed at over 300 U.S. as of 2025, they support wildlife hazard management without navigational functions. Industrial applications demonstrate radiolocation in controlled environments through Real-Time Location Systems (RTLS) using (UWB) technology, as seen in ' WhereTag systems for warehouse . These systems achieve centimeter-level accuracy (under 10 cm) by leveraging short-pulse signals for precise time-of-flight measurements in multipath-prone indoor settings. In contexts, the AN/TPY-2 radar provides forward-based X-band (8-12 GHz) surveillance for , detecting and tracking ballistic threats with resolutions down to 0.1 meters at ranges exceeding 1,000 km. First deployed in the mid-2000s, such as to in , it supports terminal-mode operations for intercept guidance in integrated air defense networks. By 2025, New Radio (NR-V2X) represents an advanced operational case for vehicular radiolocation, combining millimeter-wave with cellular sidelink communications in sub-6 GHz bands for and collision avoidance. Standardized in Release 16 (2020) and enhanced in Release 17 (2022), NR-V2X enables cooperative perception where vehicles share data to maintain formations with inter-vehicle spacing under 10 meters and reaction times below 100 ms. This integration reduces collision risks in high-density traffic by fusing -derived positions with V2X messages, as demonstrated in European and U.S. pilot deployments achieving over 99% reliability in urban scenarios.

References

  1. https://life.itu.int/radioclub/rr/art1.pdf
  2. https://www.researchgate.net/publication/366875516_Radiolocation_and_Its_Basic_Principles
  3. https://ieeexplore.ieee.org/document/5282288
  4. https://www.ecfr.gov/current/title-47/chapter-I/subchapter-D/part-90/subpart-F
  5. https://cept.org/documents/cpg15-pt-c/2210/cpg-ptc-11-082-annex-13_ai-1_14-draft-brief
  6. https://www.federalregister.gov/documents/2024/08/05/2024-16638/allocation-of-spectrum-for-non-federal-space-launch-operations-federal-earth-stations-communicating
  7. https://www.ntia.gov/fcc-filing/2025/ntia-comments-facilitating-opportunities-advanced-air-mobility
  8. https://www.itu.int/pub/R-REG-RR-2024
  9. https://www.itu.int/dms_pub/itu-r/opb/rep/R-REP-P.2346-4-2021-PDF-E.pdf
  10. https://www.itu.int/dms_pub/itu-r/opb/hdb/R-HDB-32-1998-PDF-E.pdf
  11. https://ethw.org/Radio_Direction_Finder
  12. https://www.aps.org/publications/apsnews/201911/history.cfm
  13. https://www.researchgate.net/publication/224223493_On_the_origins_of_RF-based_location
  14. https://ethw.org/Chain_Home
  15. https://www.microwavejournal.com/articles/28299-the-infamous-pearl-harbor-radar
  16. https://www.worldradiohistory.com/BOOKSHELF-ARH/Regulatory/International-Radio-Regulations-1947.pdf
  17. https://pubs.aip.org/aip/rsi/article/87/4/041502/361045/Contributed-Review-Source-localization-algorithms
  18. https://web.gps.caltech.edu/classes/ge111/Docs/GPSbasics.pdf
  19. https://www.radartutorial.eu/01.basics/Distance-determination.en.html
  20. https://www.ee.cityu.edu.hk/~hcso/tsp_4_04_1.pdf
  21. https://www.itu.int/dms_pub/itu-r/opb/rep/R-REP-SM.2211-2-2018-PDF-E.pdf
  22. https://dl.cdn-anritsu.com/en-us/test-measurement/files/Application-Notes/Application-Note/11410-01009D.pdf
  23. https://www.icact.org/upload/2012/0050/20120050_finalpaper.pdf
  24. https://pmc.ncbi.nlm.nih.gov/articles/PMC4883398/
  25. https://www.mdpi.com/1999-4893/18/7/438
  26. https://ieeexplore.ieee.org/document/8226757
  27. https://www.itu.int/en/ITU-D/Regional-Presence/ArabStates/Documents/events/2020/SM/Pres/S2D2Direction%20Finding%20Basics%20and%20Methods.pdf
  28. https://ieeexplore.ieee.org/document/8751643
  29. https://www.itu.int/dms_pubrec/itu-r/rec/m/R-REC-M.1730-0-200506-S%21%21PDF-E.pdf
  30. https://www.sciencedirect.com/topics/computer-science/path-loss-model
  31. https://pmc.ncbi.nlm.nih.gov/articles/PMC6165244/
  32. https://www.etsi.org/newsroom/press-releases/2520-etsi-publishes-first-report-on-isac-use-cases-for-6g
  33. https://search.itu.int/history/HistoryDigitalCollectionDocLibrary/1.49.48.en.101.pdf
  34. https://www.itu.int/en/itunews/Documents/2024/2024-01/2024_ITUNewsMag01-en.pdf
  35. https://www.fcc.gov/sites/default/files/fcctable.pdf
  36. https://search.itu.int/history/HistoryDigitalCollectionDocLibrary/1.7.48.en.100.pdf
  37. https://www.uba.be/sites/default/files/media/files/itu_handbook-on-amateur-and-amateur-satellite-services-v2014.pdf
  38. https://www.5gamericas.org/wp-content/uploads/2024/10/The-6G-Upgrade-in-the-7-8-GHz-Spectrum-Id.pdf
  39. https://www.federalregister.gov/documents/2020/01/16/2019-28483/wireless-e911-location-accuracy-requirements
  40. https://content.u-blox.com/sites/default/files/products/documents/GPS-Compendium_Book_%2528GPS-X-02007%2529.pdf
  41. https://repository.rit.edu/cgi/viewcontent.cgi?article=7480&context=theses
  42. https://www.3gpp.org/ftp/tsg_ran/tsg_ran/TSGR_25/Docs/PDF/RP-040347.pdf
  43. https://www.3gpp.org/technologies/nr-positioning-2
  44. https://d1p0gxnqcu0lvz.cloudfront.net/documents/Nokia_The_Evolution_of_5G_New_Radio_Positioning_Technologies_White_Paper_EN.pdf
  45. https://ieeexplore.ieee.org/document/6569137/
  46. https://www.archivemarketresearch.com/reports/5g-embb-362971
  47. https://www.apple.com/newsroom/2024/11/apples-find-my-enables-sharing-location-of-lost-items-with-third-parties/
  48. https://europa.eu/youreurope/citizens/travel/security-and-emergencies/emergency-assistance-vehicles-ecall/index_en.htm
  49. https://eur-lex.europa.eu/eli/reg_del/2025/1871/oj/eng
  50. https://www.ntia.gov/sites/default/files/2023-11/6_2021_edition_rev_2023.pdf
  51. https://www.spaceforce.mil/News/article/2166101/gps-celebrates-25th-year-of-operation/
  52. https://www.gps.gov/space-segment
  53. https://glonass-iac.ru/en/about_glonass/
  54. https://novatel.com/an-introduction-to-gnss/gnss-constellations/galileo
  55. https://gnss-sdr.org/osnma/
  56. https://www.gsc-europa.eu/system-service-status/constellation-information
  57. https://www.eoportal.org/satellite-missions/sar-lupe
  58. https://www.thespacereview.com/article/790/1
  59. https://aero-news.net/AnnTicker.cfm?do=main.textpost&id=C40479DA-8BC8-4B1C-AE62-2F9FCEC6677E
  60. https://www.space.com/spacex-starlink-satellites.html
  61. https://www.esri.com/about/newsroom/arcuser/differential-gps-explained
  62. https://www.ion.org/publications/abstract.cfm?articleID=14096
  63. https://www.ll.mit.edu/media/6946
  64. https://training.weather.gov/nwstc/NEXRAD/RADAR/Section1-2.html
  65. https://pds-geosciences.wustl.edu/radiosciencedocs/urn-nasa-pds-radiosci_documentation/DOCUMENT/asmar.2014.pdf
  66. https://www.icams-portal.gov/resources/ofcm/fmh/FMH11/fmh-11B-2005.pdf
  67. https://www.faa.gov/air_traffic/technology/asr-11
  68. https://www.ntia.gov/files/ntia/publications/compendium/2700.00-2900.00_01MAR14-1.pdf
  69. https://www.eoportal.org/satellite-missions/terrasar-x
  70. https://www.dlr.de/en/eoc/research-transfer/topics/missions/terrasar-x
  71. https://www.gminsights.com/industry-analysis/4d-imaging-radar-market
  72. https://www.nxp.com/applications/RADAR-SYSTEMS
  73. https://www.marketsandmarkets.com/Market-Reports/automotive-radar-market-75536718.html
  74. https://pmc.ncbi.nlm.nih.gov/articles/PMC9229601/
  75. https://www.siemens.com/us/en/products/automation/industrial-identification/simatic-rtls.html
  76. https://ieeexplore.ieee.org/document/10489920/
  77. https://arxiv.org/pdf/2504.13363
  78. https://ioos.noaa.gov/project/hf-radar/
  79. https://www.itu.int/rec/R-REC-F/en
  80. https://www.ursanav.com/wp-content/uploads/eLoran-for-e-Navigation-PPT-2014.pdf
  81. http://www.rdfproducts.com/an001_apl_01.pdf
  82. https://www.ti.com/lit/ds/symlink/awrl6432.pdf
  83. https://www.defenseadvancement.com/feature/why-inertial-navigation-systems-are-crucial-for-mobile-radar-in-defense-applications/
  84. https://www.geophysical.com/products/lifelocator-trx
  85. https://merlo.io/assets/pdf/APS_SDC_2020.pdf
  86. https://www.sciencedirect.com/science/article/pii/S2405959525001626
  87. https://www.navcen.uscg.gov/?pageName=AIS
  88. https://www.imo.org/en/OurWork/Safety/Pages/AIS.aspx
  89. https://www.robinradar.com/markets/airport-bird-control-solutions
  90. https://detect-inc.com/bird-detection-radar-solutions/
  91. https://www.globalsecurity.org/space/systems/an-tpy-2.htm
  92. https://www.qualcomm.com/media/documents/files/smart-transportation-presentation.pdf
  93. https://www.3gpp.org/DynaReport/TDocExMtg-R2-103b-18803.htm
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