Terms Archive

GNSS Terms and Definitions

Accuracy

Positioning accuracy is a fundamental metric in Global Navigation Satellite System (GNSS) technology that measures…

ADAS

Advanced Driver Assistance Systems (ADAS) represent a transformative category of electronic safety technologies integrated into…

Learn More

Alert Limit

The Alert Limit (AL) is a critical safety parameter in positioning system integrity frameworks that…

Learn More

ASIL

Automotive Safety Integrity Level (ASIL) is a risk classification system defined by the ISO 26262…

Learn More

ASPICE

Automotive SPICE (Software Process Improvement and Capability dEtermination), commonly abbreviated as ASPICE or A-SPICE, is…

Learn More

Baseline

In Real-Time Kinematic (RTK) positioning, the baseline refers to the three-dimensional vector distance between a…

Learn More

BeiDou

The BeiDou Navigation Satellite System (BDS) is China’s independent global navigation satellite system, developed and…

Learn More

Constellation

In satellite navigation terminology, a constellation refers to a coordinated group of satellites working together…

Learn More

Continuously Operating Reference Station (CORS)

A Continuously Operating Reference Station (CORS) is a permanently installed, precisely surveyed GNSS ground station…

Learn More

Datum

A geodetic datum is a mathematical reference framework that enables the precise definition of geographic…

Learn More

Dead Reckoning

Dead reckoning is a fundamental navigation technique that estimates a current position by mathematically projecting…

Learn More

Differential GNSS (DGNSS)

Differential GNSS (DGNSS) is a positioning enhancement technique that significantly improves standard satellite navigation accuracy…

Learn More

Earth-Centered, Earth-Fixed (ECEF)

The Earth-Centered, Earth-Fixed (ECEF) coordinate system is a three-dimensional Cartesian reference frame that serves as…

Learn More

EKF

The Extended Kalman Filter (EKF) is a mathematical algorithm that serves as the de facto…

Learn More

Ellipsoid

An ellipsoid is a three-dimensional geometric shape that serves as the mathematical model for representing…

Learn More

Ellipsoidal Height

Ellipsoidal height, also known as geodetic height or height above ellipsoid (HAE), is a vertical…

Learn More

Ephemeris

Ephemeris data comprises the precise orbital parameters broadcast by navigation satellites that enable GNSS receivers…

Learn More

Epoch

In GNSS and geodetic applications, an epoch refers to a specific instant in time used…

Learn More

Fixed RTK

Fixed RTK (Real-Time Kinematic) represents the highest-accuracy positioning mode achievable with carrier-phase differential GNSS techniques,…

Learn More

FKP

Flächenkorrekturparameter (FKP), which translates from German as ‘area correction parameters,’ is a Network RTK correction…

Learn More

Float RTK

Float RTK (Real-Time Kinematic) is an intermediate GNSS positioning state where the receiver processes carrier…

Learn More

Functional Safety

Functional safety is a critical engineering discipline focused on ensuring that automated systems operate correctly…

Learn More

Galileo

Galileo is the European Union’s global navigation satellite system (GNSS), representing Europe’s independent contribution to…

Learn More

Geofencing

Geofencing is a location-based technology that creates virtual boundaries around real-world geographic areas, enabling automated…

Learn More

Geoid

The geoid is a fundamental concept in geodesy representing an equipotential surface of Earth’s gravity…

Learn More

GGA

GGA is one of the most commonly used NMEA 0183 sentence types in GNSS applications,…

Learn More

GLONASS

GLONASS (Globalnaya Navigazionnaya Sputnikovaya Sistema, or Global Navigation Satellite System) is Russia’s global satellite navigation…

Learn More

GNSS

Global Navigation Satellite System (GNSS) is the universal term encompassing all satellite-based positioning, navigation, and…

Learn More

GPP NULL Antenna

The GPP NULL Antenna, also referred to as ADVNULLANTENNA, represents a specialized antenna calibration concept…

Learn More

GPS

The Global Positioning System (GPS) is the United States’ satellite-based navigation system, operated by the…

Learn More

GRS

The Geodetic Reference System (GRS) is a standardized framework that defines the fundamental parameters used…

Learn More

GSA

GSA is an NMEA 0183 sentence type that provides detailed information about the satellites currently…

Learn More

HAE

Height Above Ellipsoid (HAE), also known as ellipsoidal height or geodetic height, is the vertical…

Learn More

Hardware-in-the-loop Testing

Hardware-in-the-Loop (HIL or HITL) testing is an advanced validation methodology that evaluates real GNSS hardware,…

Learn More

Hatanaka

Hatanaka compression is a specialized data compression algorithm designed specifically for GNSS observation files in…

Learn More

HTDP

HTDP (Horizontal Time-Dependent Positioning) is specialized software developed and maintained by the U.S. National Geodetic…

Learn More

IGS

The International GNSS Service (IGS) is a voluntary federation of over 200 contributing organizations worldwide…

Learn More

Inertial Measurement Unit (IMU)

An Inertial Measurement Unit (IMU) is an electronic sensor assembly that measures linear acceleration and…

Learn More

INS

An Inertial Navigation System (INS) is a self-contained navigation technology that determines position, velocity, and…

Learn More

Integrity

Integrity in GNSS positioning refers to the system’s ability to provide timely and accurate warnings…

Learn More

Integrity Risk

Integrity Risk is a quantitative measure of the probability that a positioning system will provide…

Learn More

Ionospheric Delay

Ionospheric delay is one of the largest error sources affecting GNSS positioning accuracy, caused by…

Learn More

ISO 21434

ISO/SAE 21434 is the international standard for automotive cybersecurity engineering, providing a comprehensive framework for…

Learn More

ISO 21448

ISO 21448, titled ‘Road Vehicles, Safety of the Intended Functionality (SOTIF),’ addresses a critical safety…

Learn More

ISO 26262

ISO 26262 is the international standard for functional safety of electrical and electronic systems in…

Learn More

ITRF

The International Terrestrial Reference Frame (ITRF) is the most accurate and widely adopted global geodetic…

Learn More

L-Band

L-band refers to a specific range of radio frequencies in the electromagnetic spectrum, spanning approximately…

Learn More

L1

The L1 signal is the primary civilian GPS frequency, broadcasting at 1575.42 MHz, and represents…

Learn More

L2

The L2 signal is the second GPS frequency, broadcasting at 1227.60 MHz, originally designated for…

Learn More

L5

The L5 signal represents the newest and most advanced civilian GPS frequency, broadcasting at 1176.45…

Learn More

LLA

LLA (Latitude, Longitude, and Altitude) is the most common format for expressing geographic coordinates, representing…

Learn More

Measurement Engine (ME)

The Measurement Engine (ME) is a fundamental component of GNSS receiver architecture responsible for acquiring…

Learn More

MSM

Multiple Signal Messages (MSM) represent a modern, standardized format within the RTCM 3.x protocol for…

Learn More

Multi-Constellation

Multi-constellation GNSS refers to the use of satellite signals from two or more Global Navigation…

Learn More

Multipath

Multipath is a significant error source in GNSS positioning that occurs when satellite signals reach…

Learn More

NAVDATA

NAVDATA, or Navigation Data, refers to the digital message content broadcast by GNSS satellites that…

Learn More

Network RTK

Network RTK is an advanced GNSS positioning technique that delivers centimeter-level accuracy over wide geographic…

Learn More

NMEA

NMEA (National Marine Electronics Association) is the standardized communication protocol used by virtually all GNSS…

Learn More

NTRIP

NTRIP (Networked Transport of RTCM via Internet Protocol) is the industry-standard protocol for streaming GNSS…

Learn More

NTRIP Caster

An NTRIP Caster is the central server component in the NTRIP (Networked Transport of RTCM…

Learn More

Observations

In GNSS terminology, observations refer to the raw measurements that a receiver extracts from satellite…

Learn More

Orthometric Height

Orthometric height is the vertical distance measured from the geoid, an equipotential surface of Earth’s…

Learn More

OSR

Observation Space Representation (OSR) is a method of encoding and transmitting GNSS corrections where all…

Learn More

PDOP

Position Dilution of Precision (PDOP) is a dimensionless metric that quantifies how satellite geometry affects…

Learn More

Position, Velocity, and Time (PVT)

Position, Velocity, and Time (PVT) represents the three fundamental outputs that GNSS receivers provide from…

Learn More

Positioning Engine (PE)

A Positioning Engine (PE) is the core software component responsible for computing position, velocity, time…

Learn More

Positioning, Navigation, and Timing (PNT)

Positioning, Navigation, and Timing (PNT) is the comprehensive term for the three interdependent capabilities that…

Learn More

Post-Processing Kinematic (PPK)

Post-Processing Kinematic (PPK) is a high-precision GNSS positioning technique that achieves centimeter-level accuracy by combining…

Learn More

PPP-RTK

PPP-RTK is a hybrid GNSS correction technique that combines the global scalability of Precise Point…

Learn More

Precise Point Positioning (PPP)

Precise Point Positioning (PPP) is an advanced GNSS positioning technique that achieves centimeter- to decimeter-level…

Learn More

Precision

vPrecision in GNSS positioning describes the consistency, repeatability, or clustering of position measurements under unchanged…

Learn More

Protection Level

Protection Level (PL) is a statistical bound that quantifies the maximum likely error in a…

Learn More

Pseudorange

Pseudorange is the fundamental measurement type in GNSS positioning, representing the apparent distance between a…

Learn More

QZSS

The Quasi-Zenith Satellite System (QZSS) is Japan’s regional satellite navigation system designed to augment GPS…

Learn More

Reference Frame

A reference frame (or geodetic reference frame) is a precisely defined coordinate system that provides…

Learn More

RINEX

RINEX (Receiver Independent Exchange Format) is the standardized ASCII format for storing and exchanging raw…

Learn More

Rover

In GNSS terminology, a rover is the mobile positioning component in a differential correction system,…

Learn More

RTCM

RTCM (Radio Technical Commission for Maritime Services) refers both to the international standards organization that…

Learn More

RTK

Real-Time Kinematic (RTK) is a GNSS positioning technique that achieves centimeter-level accuracy in real-time by…

Learn More

SBAS

Satellite-Based Augmentation System (SBAS) is a regional augmentation technology that improves GNSS accuracy, integrity, and…

Learn More

Single Base RTK

Single-base RTK is the traditional form of Real-Time Kinematic positioning where a mobile rover receives…

Learn More

Software-in-the-Loop Testing

Software-in-the-Loop (SIL or SITL) testing is a verification methodology that executes positioning software in a…

Learn More

SOTIF

SOTIF (Safety of the Intended Functionality) is a safety engineering concept and standard, formalized in…

Learn More

Spheroid

A spheroid (also called ellipsoid of revolution) is a three-dimensional geometric shape generated by rotating…

Learn More

SSR

State Space Representation (SSR) is a correction format methodology where individual GNSS error sources, satellite…

Learn More

Station

A GNSS station (or base station) is a fixed installation consisting of a permanently-mounted GNSS…

Learn More

TACAN

TACAN (Tactical Air Navigation) is a military navigation system that provides aircraft with bearing and…

Learn More

Target Integrity Risk

Target Integrity Risk (TIR) is the specified maximum acceptable probability that a positioning system will…

Learn More

Tropospheric Delay

Tropospheric delay is a GNSS error source caused by signal propagation through the troposphere, the…

Learn More

TTFF

Time to First Fix (TTFF) measures how quickly a GNSS receiver acquires satellite signals and…

Learn More

UTM

Universal Transverse Mercator (UTM) is a global map projection system that divides Earth’s surface into…

Learn More

V2X (Vehicle-to-Everything)

Vehicle-to-Everything (V2X) communication is a wireless technology framework enabling vehicles to exchange information with surrounding…

Learn More

VRS

Virtual Reference Station (VRS) is a Network RTK technique that generates synthetic observation data for…

Learn More

WAAS

The Wide Area Augmentation System (WAAS) is the United States’ Satellite-Based Augmentation System (SBAS), operated…

Learn More

WGS

The World Geodetic System (WGS) is a global reference framework that defines the coordinate system,…

Learn More

Wheel Odometry

Wheel odometry is a navigation sensing technique that measures vehicle travel distance by counting wheel…

Learn More