Glossary
AHRS – Attitude and Heading Reference System
Attitude & Heading Reference System (AHRS) is a crucial technology in modern aviation and maritime navigation. It provides essential information about an aircraft or vessel’s orientation and heading, ensuring safe and accurate navigation.
Go to full definition →Antenna gain
GNSS antenna gain describes the antenna’s ability to receive satellite signals from specific directions with varying strength. It plays a crucial role in determining signal quality, reception range, and positioning accuracy. Unlike highly directional antennas, GNSS antennas are designed to provide consistent gain across the sky to track multiple satellites simultaneously. A well-balanced gain pattern helps minimize signal loss, reduce multipath interference, and maintain reliable performance in diverse environments. Understanding antenna gain is essential for selecting the right GNSS antenna for applications such as surveying, navigation, geodesy, and autonomous systems.
Go to full definition →Antenna polarization
Antenna polarization defines the orientation of an antenna’s electric field during signal transmission or reception. It plays a crucial role in wireless communication by affecting signal strength, quality, and reliability. Common types include linear, circular, and elliptical polarization, each suited to specific applications. Matching polarization between transmitting and receiving antennas maximizes signal efficiency and minimizes losses. Additionally, environmental factors and antenna orientation can influence polarization performance. Understanding antenna polarization is essential for designing and optimizing communication systems, navigation receivers, and radar technologies to ensure effective and reliable signal transmission in various conditions.
Go to full definition →Antenna radiation pattern
The GNSS antenna radiation pattern describes how the antenna receives signals from different directions in space. It is a key factor in determining the antenna’s ability to track satellites across the sky and maintain signal quality. A well-designed radiation pattern ensures strong gain toward the zenith and adequate coverage toward the horizon while minimizing interference from unwanted directions. This directly impacts positioning accuracy, signal reliability, and resistance to multipath effects. Understanding and optimizing the radiation pattern is essential for high-performance GNSS applications such as surveying, aviation, autonomous vehicles, and scientific research.
Go to full definition →Anti-jamming
Anti-jamming refers to techniques and technologies designed to protect satellite signals, especially GNSS signals, from intentional or unintentional interference. Because these signals are weak by the time they reach receivers, they are vulnerable to disruption from jamming devices that block or overwhelm the signal. Anti-jamming systems detect, filter, or avoid these interfering signals to ensure continuous, accurate navigation and communication. These methods include using directional antennas, advanced signal processing, frequency diversity, and integration with other sensors, helping maintain reliable performance even in challenging or hostile environments. An anti-jamming system protects GPS and satellite signals from low-power jammers, which are easily accessible online and can disrupt positioning and timing over wide areas.
Go to full definition →Anti-jamming device
An anti-jamming device is a critical component in modern navigation systems, designed to protect against signal interference that can disrupt GNSS-based positioning and timing. As satellite signals are inherently weak when they reach Earth, they are highly vulnerable to jamming—intentional or unintentional transmission of radio frequency signals that overpower or block the original signal. Anti-jamming devices use advanced techniques such as beamforming, filtering, and signal processing to detect, suppress, or reject interference. These devices ensure reliable and accurate navigation in challenging environments, making them essential for defense, aviation, maritime, and autonomous applications where continuous GNSS availability is vital.
Go to full definition →Attitude in navigation
In navigation, attitude refers to the orientation of a vehicle or object relative to a fixed frame of reference, which is typically defined by three rotational axes: pitch, roll, and yaw.
Go to full definition →Backpack-based surveying
Backpack-based surveying is a modern, mobile mapping method that combines advanced sensors in a wearable system. Designed for flexibility and efficiency, it allows users to collect accurate spatial data while walking through areas that are difficult to access by vehicle, drone, or traditional equipment. Equipped with technologies like GNSS, LiDAR, cameras, and inertial sensors, backpack systems are ideal for mapping forests, urban environments, tunnels, and indoor spaces. This approach streamlines data collection, reduces setup time, and enables high-resolution 3D modeling in both open and GNSS-denied environments.
Go to full definition →Backward processed inertial path
Backward processed inertial path refers to the technique of computing a vehicle’s trajectory by processing inertial data in reverse time order. This method starts from a known endpoint—such as when GNSS signal is reacquired after an outage—and calculates the path backwards. It provides an alternative perspective on position estimation, particularly useful when combined with the forward processed path. By comparing both paths, engineers can better identify and reduce drift errors in GNSS-aided inertial navigation systems, improving overall accuracy in challenging environments.
Go to full definition →Backward processing
Backward processing is a GNSS post-processing technique that calculates position data from the end of a survey toward the beginning. Unlike forward processing, which works chronologically, backward processing analyzes data in reverse time order. This method enhances accuracy by correcting errors that may occur near the end of a dataset. It proves especially useful when combined with forward processing, allowing users to merge results and produce a more reliable trajectory. Backward processing is ideal for applications that require high precision, such as mobile mapping, UAV missions, and marine surveys, where post-mission data refinement is critical.
Go to full definition →Baud rate
Baud rate plays a critical role in inertial navigation systems, defining the speed at which data transfers between sensors and processing units. Proper baud rate selection ensures accurate, timely communication of motion, orientation, and velocity data. Optimizing this parameter is essential for reliable performance in high-dynamic and real-time navigation applications.
Go to full definition →BeiDou
Beidou is the chinese global positioning system, offering global positioning, navigation, and timing services. Named after the Big Dipper constellation, Beidou represents China's significant advancement in space infrastructure and technology.
Go to full definition →Body Frame
The sensor (body) coordinate frame, often called the body frame or vehicle frame, serves as a reference frame fixed to a moving platform, such as a drone, car, missile, or underwater vehicle. Engineers use this frame to describe the motion and orientation of the platform relative to itself, making it essential for navigation, control, and sensor fusion.
Go to full definition →Built-in filters
The incorporation of built-in filters within GNSS antennas is imperative for the safeguarding of receivers against signal interference, thereby ensuring the maintenance of precise positioning. These filters are designed to block unwanted frequencies, such as cellular, radio, or Wi-Fi signals, while permitting only GNSS signals to pass through. It is important to note that satellite signals arrive at very low power levels; therefore, even minor interference has the potential to affect performance. The integration of filters directly into the antenna has been demonstrated to enhance signal quality, mitigate noise, and streamline the system. This built-in protection is of particular importance in urban or industrial environments where signal congestion is prevalent. It is imperative to note that reliable filtering is essential for ensuring stable GNSS performance across all applications.
Go to full definition →Dead reckoning navigation
Dead reckoning is a navigation technique used to determine one's current position by using a previously known position and calculating the course based on speed, time, and direction traveled.
Go to full definition →DVL – Doppler Velocity Log
A Doppler Velocity Log (DVL) is an acoustic sensor used to measure the velocity of an underwater vehicle relative to the seafloor or water column. It operates using the Doppler effect, where sound waves emitted from the DVL's transducers reflect off surfaces and return with a frequency shift proportional to the vehicle's motion. By analyzing this shift, the DVL calculates the velocity in three dimensions (surge, sway, and heave), enabling accurate underwater navigation and positioning.
Go to full definition →ECEF: Earth-Centered, Earth-Fixed Frame
The Earth-Centered, Earth-Fixed (ECEF) frame is a global coordinate system used to represent positions on or near Earth. It is a rotating reference frame that remains fixed relative to Earth’s surface, meaning it moves with the planet as it rotates. Engineers, scientists, and navigation systems use ECEF coordinates to track positions accurately in a global context.
Go to full definition →EKF – Extended Kalman filter
The Extended Kalman Filter (EKF) is an algorithm used for estimating the state of a dynamic system from noisy measurements. It extends the Kalman Filter to accommodate non-linear systems, which are common in real-world navigation scenarios. While the standard Kalman Filter assumes linearity and Gaussian noise, the EKF linearizes the non-linear system around the current estimate, enabling it to work effectively in more complex environments.
Go to full definition →FOG – Fiber optical gyroscope
An optical gyroscope, such as a fiber-optic gyroscope (FOG), measures rotation by using the interference of light rather than moving parts. It operates based on the Sagnac effect, detecting changes in orientation as light travels through long coils of optical fiber—sometimes several kilometers in length. This design offers high precision and reliability, making optical gyroscopes ideal for navigation systems in aerospace, marine, and defense applications.
Go to full definition →Forward processed inertial path
The forward processed inertial path represents the trajectory computed from inertial sensor data in real-time. This method processes data sequentially from start to finish, using acceleration and angular rate measurements to estimate position, velocity, and orientation. While it enables continuous navigation even during GNSS outages, the solution can accumulate drift over time without external corrections. Forward processing forms the foundation of inertial navigation and is essential for real-time tracking in GPS-denied environments.
Go to full definition →Forward processing
Forward processing is a technique used in GNSS data post-processing to calculate position and trajectory from the start to the end of a survey. By analyzing data in chronological order, it estimates location changes over time using satellite signals, correction models, and sensor fusion. This method plays a key role in improving accuracy for mapping, surveying, and navigation tasks, especially in post-mission workflows.
Go to full definition →Forwards-backwards paths overlaid
Forwards-backwards paths overlay combines navigation data processed in both directions to improve positioning accuracy during GNSS outages. By merging forward and backward inertial solutions, the system minimizes drift and corrects errors that typically occur when GNSS signals are unavailable. This technique enhances overall data quality, especially in challenging environments like tunnels, urban canyons, or forests.
Go to full definition →Forwards-backwards processing
Forwards/backwards processing is a post-processing technique that enhances positioning accuracy by analyzing inertial and GNSS data in both directions. The forward processed inertial path calculates movement based on real-time data, accumulating drift over time. The backwards processed inertial path starts from a known endpoint, reversing the data to identify drift from the opposite direction. By combining both, the forwards/backwards paths overlaid provide a refined solution that minimizes error and improves navigation performance, especially in GNSS-denied environments like tunnels or urban canyons.
Go to full definition →Fugro Marinestar
Fugro Marinestar ® delivers high-precision GNSS positioning services tailored to the unique demands of industries such as marine construction, dredging, hydrography, naval operations, wind farm development, and oceanographic research. With over 30 years of expertise in satellite-based positioning and continuous technological advancements, Marinestar® provides cutting-edge, dependable solutions designed for critical marine applications. Multiple GNSS constellations […]
Go to full definition →Galileo: satellite navigation systems
Galileo is Europe’s global satellite navigation system. It delivers accurate positioning and timing services worldwide. The European Union and ESA developed and operate Galileo. They created it to offer independent and reliable navigation support. Galileo complements systems like GPS, GLONASS, and Beidou.
Go to full definition →Georeferencing
Georeferencing is the process of aligning spatial data, such as maps, aerial imagery, or scanned documents, to a specific coordinate system so that it accurately corresponds to real-world locations.
Go to full definition →GLONASS: Russian global positioning system
GLONASS is a global navigation satellite system operated by Russia. It is designed to provide accurate positioning, navigation, and timing services worldwide. Similar to other global navigation systems like GPS, Galileo, and Beidou, GLONASS uses a network of satellites to deliver precise location data to users on the ground.
Go to full definition →GNSS – Global Navigation Satellite System
GNSS (Global Navigation Satellite System) refers to a network of satellites that work together to provide accurate positioning, navigation, and timing information globally. GNSS includes several different systems, such as GPS, GLONASS, Galileo, and Beidou, each contributing to the overarching goal of delivering precise spatial data to users across the world.
Go to full definition →GNSS antennas
GPS antennas and GNSS antennas play a crucial role in satellite navigation systems by capturing signals from satellites orbiting the Earth. These antennas serve as the primary gateway for receiving positioning, navigation, and timing data essential for applications ranging from everyday smartphone navigation to high-precision surveying and autonomous vehicle guidance. While GPS antennas focus specifically on the Global Positioning System, GNSS antennas support multiple satellite constellations like GPS, Galileo, GLONASS, and BeiDou, offering enhanced accuracy and reliability. Understanding how these antennas work and their key features helps users select the right solution for their specific navigation needs.
Go to full definition →GNSS constellations
Satellite Constellation refers to a group of satellites working together to achieve a common objective, such as providing global coverage or enhancing communication and navigation services. These constellations are strategically designed to ensure continuous and reliable service by ensuring that satellites work in coordination, often in specific orbital patterns.
Go to full definition →GNSS frequencies
GNSS frequencies are specific radio bands used by satellite navigation systems to transmit signals to receivers on Earth. These frequencies carry critical information that enables precise positioning, navigation, and timing. Each GNSS constellation—such as GPS, Galileo, GLONASS, and BeiDou—uses its own set of frequencies to ensure reliable global coverage. Multi-frequency GNSS receivers can access multiple bands to improve accuracy, correct signal delays, and enhance performance in challenging environments. Understanding GNSS frequencies is essential for designing receivers, antennas, and systems that support high-precision and multi-constellation navigation applications.
Go to full definition →GNSS signals
GNSS signals are radio waves transmitted by navigation satellites to provide users on Earth with accurate position, velocity, and time information. Each signal carries essential data, including satellite identification, timing, and orbital information, which allows GNSS receivers to calculate precise locations. These signals operate on specific frequencies and use unique modulation techniques to support civilian, commercial, and military applications. With multiple GNSS constellations now active—such as GPS, Galileo, GLONASS, and BeiDou—users benefit from enhanced accuracy, reliability, and availability through combined, multi-frequency GNSS signals across various environments and conditions.
Go to full definition →GPS – Global Positioning System
Global Positioning System or GPS is a satellite-based navigation system that provides location and time information anywhere on Earth. Initially developed by the U.S. Department of Defense for military navigation, GPS has become a crucial technology for a wide range of civilian applications, including navigation, mapping, and time synchronization.
Go to full definition →Gyrocompass
A gyrocompass is a highly specialized device used for determining direction with remarkable accuracy. Unlike magnetic compasses, which rely on the Earth's magnetic field, a gyrocompass uses the principles of gyroscopic motion to find true north.
Go to full definition →Gyroscope
A gyroscope in navigation is a device that measures angular velocity or rotational movement around a specific axis. By detecting changes in orientation, gyroscopes help maintain and control the stability and direction of vehicles, aircraft, and spacecraft. They are essential for systems that require precise control of movement and orientation, such as autopilot systems, inertial navigation systems (INS), and stabilization systems.
Go to full definition →Heading method
Heading refers to the direction in which a vehicle or vessel is pointed relative to a reference direction, typically true north or magnetic north.
Go to full definition →Heave
Heave in navigation refers to the vertical movement of a vessel or platform caused by ocean waves and swell. Unlike pitch or roll, which involve rotational motion, heave represents purely up-and-down displacement. Understanding heave is essential for maritime operations, offshore drilling, and precise survey activities. It directly affects vessel stability, operational accuracy, and crew safety. Accurate measurement and compensation of heave ensure reliable navigation, improve equipment performance, and maintain operational efficiency. In modern marine operations, advanced sensors, heave compensation systems, and predictive models are used to monitor and manage vertical motion, allowing vessels and platforms to operate safely and precisely in dynamic sea conditions.
Go to full definition →IMU – Inertial Measurement Unit
Inertial Measurement Units (IMU) are fundamental components in modern navigation and motion tracking systems. An Inertial Measurement Unit (IMU) is an electronic device that measures and reports a body's specific force, angular rate, and sometimes the magnetic field surrounding the body, using a combination of accelerometers, gyroscopes, and sometimes magnetometers. IMUs are critical for tracking and controlling the position and orientation of various objects, from aircraft and ships to smartphones and gaming controllers. There are different types of IMU sensors: the one based on FOG (Fiber Optic Gyroscope), the RLG IMUs (Ring Laser Gyroscope), and lastly, IMU based on MEMS technology (Micro Electro-Mechanical Systems). This technology allows lower costs and low power requirements while ensuring performance. MEMS-based systems therefore combine high performance and ultra-low power in a smaller unit.
Go to full definition →Inertial reference frame
An inertial reference frame is a coordinate system in which objects follow Newton’s laws of motion without the need to account for fictitious or external forces. In other words, it is a non-accelerating frame—either at rest or moving at constant velocity—where a body remains at rest or continues in uniform motion unless acted upon by an external force. Scientists and engineers rely on inertial frames to analyze motion accurately in space, aviation, marine, and robotics systems.
Go to full definition →INS – Inertial Navigation System
Inertial Navigation System (INS), also called INS, is a navigation device that provides roll, pitch, heading, position, and velocity. This sophisticated technology determines an object’s position, orientation, and velocity without relying on external references. This self-contained navigation solution is crucial in various applications, ranging from aerospace and defense to robotics and autonomous vehicles.
Go to full definition →ITAR – International Traffic in Arms Regulations
The International Traffic in Arms Regulations (ITAR) are a set of U.S. government regulations that control the export and import of defense articles and services, including both physical items and technical data related to military use.
Go to full definition →Jammer
Jammers pose a growing and significant threat to satellite-based navigation systems across the globe. As society increasingly relies on Global Navigation Satellite Systems (GNSS) such as GPS, Galileo, GLONASS, and BeiDou for precise positioning, timing, and guidance, the risks associated with signal disruption have become more serious.
Go to full definition →Jamming
Jamming is the act of deliberately interfering with radio signals to disrupt the normal operation of communication or navigation systems. Often illegal, this activity poses serious risks by blocking or overpowering essential signals, especially those used in GPS and other critical networks. As our world grows more dependent on wireless technology, understanding and addressing the threat of jamming has become increasingly important.
Go to full definition →LiDAR – Light Detection and Ranging
LiDAR stands for Light Detection and Ranging. It is a method of measuring distances by emitting laser beams towards a target and measuring the time it takes for the beams to return to the sensor. The data collected from these measurements can then be used to generate accurate, high-resolution 3D models and maps of the environment.
Go to full definition →Low-noise amplifiers
Low-noise amplifiers (LNAs) are essential components in GNSS antennas, designed to amplify weak satellite signals without significantly increasing noise. Because GNSS signals arrive at extremely low power levels, often below the background noise, LNAs play a critical role in preserving signal integrity. By improving the signal-to-noise ratio (SNR), LNAs enhance receiver sensitivity, enabling accurate and reliable positioning even in challenging environments. Positioned close to the antenna, LNAs minimize cable losses and help maintain high signal quality throughout the system. Their performance is vital for applications requiring precise navigation, such as surveying, aviation, autonomous vehicles, and timing systems.
Go to full definition →Magnetic field
A magnetic field is a physical field that represents the magnetic influence on electric currents, moving charges, and magnetic materials. The Earth behaves like a giant magnet and it generates its own magnetic field that goes from South to North pole. Poles are not exactly aligned with the geographic North-South axis.
Go to full definition →MBES – Multibeam Echosounder
A Multibeam Echo Sounder (MBES) is a high-resolution sonar system used to map the seafloor and underwater features with exceptional precision. By emitting multiple sound beams in a wide fan shape beneath a vessel, MBES measures the time it takes for each beam to reflect off the seabed and return. This data allows it to generate detailed, three-dimensional images of underwater terrain. Widely used in hydrographic surveying, marine research, offshore engineering, and environmental monitoring, MBES provides accurate depth information essential for safe navigation, scientific analysis, and the development of maritime infrastructure.
Go to full definition →Meaconing
Meaconing is the rebroadcasting of GNSS signals to mislead navigation systems, causing receivers to calculate false positions or timings. This for of GNSS attack is a subtype of Spoofing, that involves intercepting GNSS signals and rebroadcasting them without altering the content but just with a delay.
Go to full definition →Motion compensation and position
Motion compensation and position refers to the ability of a system, typically involving sensors or devices, to adjust or compensate for movement or motion in order to maintain accurate positional information.
Go to full definition →MRU – Motion Reference Unit
A Motion Reference Unit (MRU) has been developed for the purpose of accurately tracking and reporting the movements of objects in dynamic environments such as the marine and aerospace sectors. The system is designed to measure roll, pitch, and heave motions, thereby facilitating enhanced navigation, stabilisation, and system performance in real time.
Go to full definition →Multipath Error
In inertial navigation, multipath error occurs when GNSS signals reflect off surfaces such as buildings, water, or terrain before reaching the receiver, causing signal distortion.
Go to full definition →Multipath rejection
Multipath rejection refers to a receiver or antenna system’s ability to reduce errors caused by reflected GNSS signals. When a GNSS signal travels directly from a satellite to a receiver, it provides accurate positioning data. However, nearby surfaces—such as buildings, water bodies, or metal structures—can reflect the signal, causing it to arrive at the receiver slightly later than the direct signal.
Go to full definition →Multisensor fusion
Multisensor fusion is a critical component in the environmental perception systems of driverless vehicles, enhancing safety and decision-making capabilities. By integrating data from various sensors such as cameras, LiDAR, radar, and ultrasonic devices, these systems can achieve a more comprehensive and accurate global positioning accuracy and overall system performance in different scenarios. What are the […]
Go to full definition →NAVIC – Navigation with Indian Constellation
NAVIC (Navigation with Indian Constellation) is an autonomous satellite navigation system developed by the Indian Space Research Organisation (ISRO) to provide accurate and reliable position data services to users in India and the surrounding region.
Go to full definition →NED (North-East-Down) Frame
The NED (North-East-Down) coordinate frame serves as a widely used reference system for navigation and inertial measurements. The North-East-Down (NED) frame serves as a local reference frame, defined by its ECEF coordinates. Typically, it remains fixed to the vehicle or platform and moves with the body frame. This frame positions the North and East axes in a plane tangent to Earth's surface at its current location, based on the WGS84 ellipsoid model.
Go to full definition →PCO – Phase Center Offset
Phase Center Offset (PCO) is a fundamental concept in high-precision GNSS positioning. It refers to the offset between an antenna’s physical reference point and the actual location where satellite signals are effectively received—the phase center. Since this point varies depending on signal frequency and direction, uncorrected PCO can introduce significant errors in positioning calculations. Accurate knowledge and correction of PCO are essential for applications requiring centimeter-level accuracy, such as surveying, geodesy, and precision navigation.
Go to full definition →PCV – Phase Center Variation
Phase Center Variation (PCV) is a critical factor affecting the accuracy of GNSS measurements. It refers to the variation in the location of an antenna’s phase center depending on the direction of the incoming satellite signal. Unlike the phase center offset (PCO), which is a fixed value, PCV changes with satellite elevation, azimuth, and signal frequency. These variations, if uncorrected, can introduce errors in precise positioning applications such as geodesy, surveying, and GNSS reference networks. Understanding and correcting PCV is essential to ensure reliable and consistent results in high-precision GNSS data processing.
Go to full definition →Pitch
Pitch is a fundamental navigation parameter that defines a vehicle’s nose-up or nose-down attitude. It plays a key role in ensuring stability, control, and accuracy across air, land, sea, and underwater domains. Precise pitch measurement allows aircraft to maintain safe climb and descent paths, ships to operate smoothly in waves, and autonomous systems to follow reliable trajectories. By integrating advanced sensors and algorithms, modern navigation solutions deliver accurate pitch data that supports mission-critical performance.
Go to full definition →Point Cloud
Point cloud refers to a collection of 3D points that represent the shape and structure of an environment. These points are typically generated by LiDAR or 3D scanning systems, and each point contains spatial coordinates (X, Y, Z), sometimes along with additional attributes like intensity or color. While the LiDAR sensor captures the raw spatial data, it is the inertial navigation system (INS) that provides the precise position and orientation of the sensor at every moment.
Go to full definition →PointPerfect ™​
PointPerfect™ is an advanced GNSS correction service that merges the precise responsiveness of RTK with the flexibility of PPP. Traditional RTK delivers high accuracy with minimal convergence delay but demands a nearby reference station. Conversely, PPP excels without ground infrastructure yet often suffers from long convergence times. PointPerfect™ optimizes both approaches by ensuring centimeter-level accuracy—typically achieved within seconds—without requiring a local base station. It offers broad coverage across Europe, the contiguous U.S., Canada, Brazil, South Korea, and Australia, extending up to approximately 22 km offshore. Compatible with SBG products via SPARTN or NTRIP formats (internet only; L-band requires external modem), PointPerfect™ supports firmware v3.0+ on Ellipse units and HPI products with firmware version 5.1.131-stable and above.
Go to full definition →Post-processing data
Post-processing data is a crucial step in improving the accuracy of recorded positioning and navigation information after a mission or survey. Instead of relying solely on real-time data, post-processing allows users to correct errors, apply advanced filters, and integrate additional reference information. This method is widely used in applications such as GNSS-based surveying, UAV mapping, hydrography, and precision agriculture. By analyzing stored data with specialized software, users can enhance results using techniques like forward, backward, and merged processing, making post-processing essential for achieving high-precision outcomes in challenging environments.
Go to full definition →PPK – Post Processing Kinematic
Post-Processing Kinematic is a GNSS data processing method used to achieve high-accuracy positioning by correcting errors in the raw positioning data. It is widely used in applications where precise geospatial information is critical, such as surveying, mapping, and UAV operations.
Go to full definition →PRN Code (Pseudo-Random Noise Code)
A Pseudo-Random Noise (PRN) code generates a unique binary sequence that appears random yet remains perfectly deterministic and repeatable. Navigation and communication systems such as GPS, Galileo, and BeiDou rely on these codes to distinguish satellites, compute precise ranges, and support robust spread-spectrum modulation. Each satellite broadcasts its own PRN code, enabling receivers to identify specific satellites and accurately measure signal travel time through correlation with a locally generated replica. Engineers design PRN sequences to be orthogonal, which reduces interference and enhances signal clarity. In GPS, for instance, the civilian C/A code repeats every millisecond, while the encrypted P(Y) code cycles over seven days and the M-code delivers superior anti-jamming resilience. PRN sequences typically use linear-feedback shift registers (LFSRs) to maintain pseudo-random behavior while ensuring predictability—making them both reliable and efficient for high-precision navigation.
Go to full definition →Reference Frames
A reference frame is a coordinate system used to measure positions, velocities, and accelerations of objects. It provides a fixed or moving point of reference, allowing engineers and scientists to describe motion consistently. Different applications use different reference frames depending on the required perspective.
Go to full definition →Reference station
A reference station is a fixed, high-precision location equipped with a GNSS receiver and antenna that collects positioning data to improve location data accuracy
Go to full definition →Relative position
Relative position describes the location of one object in relation to another. Unlike absolute positioning, which uses fixed coordinates such as latitude and longitude, relative positioning relies on distance and direction between reference points. This concept plays a critical role in fields like robotics, navigation, surveying, and autonomous systems, where knowing how two or more objects move or interact with each other is more important than their exact global coordinates. By using sensors or communication links, systems can calculate precise spatial relationships, enabling accurate movements, formation control, or object tracking, even in environments where GNSS signals are weak or unavailable.
Go to full definition →Roll
Roll is a fundamental motion parameter in navigation that directly influences vessel safety, stability, and performance. Defined as the side-to-side tilting of a ship around its longitudinal axis, roll is one of the most critical factors affecting seakeeping, crew comfort, and operational efficiency. Understanding and accurately measuring roll is essential in marine engineering, hydrography, offshore operations, and autonomous navigation systems. By monitoring roll behavior and applying stabilization technologies, operators can maintain course accuracy, protect equipment, and ensure mission success even in harsh sea conditions.
Go to full definition →ROS drivers
The Robot Operating System (ROS) is a set of software libraries and tools that help you build robot applications. From drivers to state-of-the-art algorithms, and with powerful developer tools, ROS has what you need for your next robotics project. And it’s all open source.
Go to full definition →RTCM – Radio Technical Commission for Maritime Services
RTCM (Radio Technical Commission for Maritime Services) is an international organization that develops standards to improve communication, navigation, and related systems for maritime safety and efficiency.
Go to full definition →RTK – Real Time Kinematic
RTK, or Real Time Kinematics, is a sophisticated positioning technology used to achieve high-precision GNSS location data in real-time.
Go to full definition →RTS: Rauch–Tung–Striebel
RTS: Rauch–Tung–Striebel requires only two steps: forward filtering and backward smoothing. It stores data efficiently and is easy to program. However, estimating the ambiguity parameter in the state vector makes improving navigation accuracy during initialization and reconvergence difficult.
Go to full definition →Satellite positioning systems
Satellite positioning systems help determine a precise location anywhere on Earth using satellite signals. These systems work globally. All satellites orbit the Earth and continuously transmit signals to receivers on the ground. These signals contain time and location data.
Go to full definition →SBAS – Satellite-based augmentation systems
Satellite-Based Augmentation Systems (SBAS) enhance GNSS positioning by providing real-time differential corrections without requiring a ground radio link. This makes SBAS an ideal solution for real-time surveys when radio communication is unavailable. By enabling the SBAS differential mode in your survey device settings, you can receive and record corrected positions directly via satellite. In regions where systems like WAAS (America), EGNOS (Europe), MSAS, or QZSS (Japan) are available, users can benefit from improved accuracy and reliability. When SBAS is active, the survey interface updates to reflect SBAS use, ensuring clear visibility of system status during data collection.
Go to full definition →Ship motion measurement
Ship motion measurement refers to the process of quantifying the six degrees of freedom that describe a vessel’s movement at sea. A ship is constantly influenced by waves, wind, and currents, which generate both translational and rotational motions. These include surge, sway, and heave, which are linear displacements, and roll, pitch, and yaw, which are angular rotations. Accurate measurement of these motions is essential for navigation, stability analysis, offshore operations, and scientific research. Modern systems rely on inertial sensors, gyroscopes, accelerometers, and GNSS receivers to capture high-precision motion data in real time. This information is used to improve vessel control, ensure crew safety, and support applications such as dynamic positioning, hydrographic surveys, and active heave compensation. By continuously monitoring ship motions, operators can anticipate challenges, optimize performance, and maintain reliable operations in demanding marine environments.
Go to full definition →SLAM – Simultaneous localization and mapping
Simultaneous Localization and Mapping (SLAM) is a core technology that enables autonomous systems to understand and navigate unknown environments. By using onboard sensors such as cameras, lidar, or IMUs, SLAM allows a device to build a map of its surroundings while determining its precise location within that map—all in real time. This powerful technique plays a critical role in applications ranging from robotics and drones to self-driving cars and augmented reality. SLAM eliminates the need for external positioning systems like GNSS, making it especially valuable in indoor, underground, or otherwise GNSS-denied environments.
Go to full definition →Spoofing
What is spoofing ? Spoofing is a sophisticated type of interference that deceives a GNSS receiver into calculating a false position. During such an attack, a nearby radio transmitter broadcasts counterfeit GPS signals that override the authentic satellite data received by the target.
Go to full definition →Spoofing mitigation
What is spoofing mitigation ? Spoofing Mitigation involves implementing methods and technologies to detect, prevent, and respond to spoofing attacks on GNSS systems. Spoofing attacks can deceive GNSS receivers by broadcasting fraudulent signals that appear to be from legitimate satellites. These attacks can lead to serious consequences, including navigational errors, loss of service, and security breaches.
Go to full definition →Subsea navigation system
Subsea navigation systems provide accurate positioning and motion tracking for underwater vehicles operating in GNSS-denied environments. These systems are essential for tasks such as seabed mapping, pipeline inspection, offshore construction, and marine research. By combining acoustic positioning, inertial sensors, Doppler velocity logs, and advanced sensor fusion algorithms, subsea navigation ensures reliable guidance in deep and complex underwater conditions. As underwater operations expand in scope and depth, robust navigation technology plays a critical role in enabling safe, efficient, and precise mission execution.
Go to full definition →Surge
Surge refers to a vessel’s forward and backward motion along its longitudinal axis, significantly impacting maritime operations and navigation. It directly affects ship speed, propulsion efficiency, and course stability. By accurately measuring and managing surge, vessels can maintain optimal performance, reduce fuel consumption, and ensure crew and cargo safety. Advanced sensors and control systems continuously monitor surge, enabling real-time corrections, motion compensation, and improved operational efficiency across commercial, defense, and offshore applications.
Go to full definition →UART – Universal Asynchronous Receiver-Transmitter
A Universal Asynchronous Receiver-Transmitter (UART) is a fundamental communication interface widely used in embedded systems. In inertial navigation systems (INS), where sensors continuously generate critical motion data, UART offers a simple yet reliable way to transfer information between IMUs and processors. By eliminating the need for a dedicated clock line and using flexible baud rates, UART ensures efficient, low-latency, and robust data exchange. This makes it an ideal choice for compact, power-constrained, and mission-critical navigation applications.
Go to full definition →VBS – Virtual Base Station
A Virtual Base Station (VBS) is a GNSS processing technique designed to enhance positioning accuracy in real-time kinematic (RTK) and post-processing applications. Instead of relying on a single, fixed physical base station, a VBS generates a virtual reference station near the rover’s location. This approach reduces positioning errors caused by atmospheric disturbances and improves overall system precision.
Go to full definition →Vibrations
Vibrations can introduce unwanted noise or distortions into the measurements because MEMS sensors are highly sensitive to external forces.
Go to full definition →VRS – Virtual Reference Station
A Virtual Reference Station (VRS) is a simulated GNSS reference point designed to enhance real-time positioning accuracy. By leveraging data from a network of continuously operating reference stations (CORS), VRS creates a localized correction signal, reducing spatial errors and improving RTK (Real-Time Kinematic) precision. This allows users to achieve centimeter-level accuracy as if a reference station were positioned at their exact location.
Go to full definition →VRU – Vertical Reference Unit
A Vertical Reference Unit (VRU) includes an inertial measurement unit (IMU) and filtering algorithms to deliver accurate Roll and Pitch angles. It uses gravity as a vertical reference to stabilize the IMU. The system combines gyroscope data with gravity measurements from accelerometers using a Kalman filter to compute Roll and Pitch. VRUs benefit from gyroscopes to maintain accurate Roll and Pitch during low to medium dynamic movements. They are simple to install and operate. However, their precision may decrease in highly dynamic conditions because they cannot fully separate linear accelerations from gravity-based measurements. A Motion Reference Unit (MRU) builds on the VRU by also providing ship motion data—Heave, Surge, and Sway—alongside Roll and Pitch, making it ideal for demanding marine applications.
Go to full definition →Yaw
Yaw is a fundamental rotational movement around the vertical axis, essential for navigation and control across diverse applications. It determines heading and directional stability, influencing how ships maintain course, how aircraft counter crosswinds, how vehicles handle corners, and how UAVs and drones navigate complex environments. By accurately measuring and managing yaw, systems can achieve improved stability, safety, and efficiency. Sensors such as gyroscopes, magnetometers, and inertial measurement units provide continuous yaw data, enabling precise control in marine, aviation, automotive, robotics, and virtual reality applications. Understanding yaw dynamics is key to ensuring reliable performance in both everyday transportation and advanced mission-critical operations.
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