Glossary
Key terms in professional surveying and geospatial technology.
GDOP is a dimensionless factor that describes how satellite geometry affects the accuracy of position measurements in GNSS surveying.
Geodesy is the scientific discipline that measures and monitors Earth's shape, size, gravitational field, and the precise positioning of points on its surface.
A geodetic datum is a reference system that defines the shape, size, and orientation of Earth used to establish precise coordinates for surveying and mapping applications.
The geoid is an equipotential surface of Earth's gravitational field that best approximates mean sea level and serves as the fundamental reference datum for orthometric height measurements in surveying.
Geoid undulation is the vertical separation between the ellipsoid and the geoid at any given location on Earth's surface.
Geomatics is the discipline of gathering, storing, processing, and delivering geographic data and information for spatial analysis and mapping applications.
Georectification is the process of aligning and transforming aerial or satellite imagery to match real-world geographic coordinates and a specific map projection system.
The process of assigning geographic coordinates to spatial data such as maps, images, or documents to align them with a known coordinate system on Earth's surface.
Geospatial data is information about physical objects and features on Earth that includes their geographic location, spatial relationships, and associated attributes.
GeoTIFF is a standardized raster image format that embeds geospatial metadata directly into TIFF files, enabling georeferenced imagery and digital elevation models in surveying and mapping applications.
A Geographic Information System (GIS) is a computer-based tool that captures, stores, analyzes, and visualizes spatial data and geographic information for surveying, planning, and decision-making applications.
GLONASS is a Russian satellite navigation system providing global positioning and timing services similar to GPS, widely used in surveying and geospatial applications.
GNSS is a satellite-based navigation system that provides precise positioning, navigation, and timing information to users worldwide through multiple constellations of orbiting satellites.
A specialized antenna that receives signals from Global Navigation Satellite System (GNSS) satellites to enable precise positioning and surveying measurements.
The point within a GNSS antenna where the electromagnetic signals are effectively received, which may differ from the physical center and must be calibrated for accurate positioning.
The measured distance and three-dimensional vector between two GNSS receiver positions, forming the foundation of relative positioning and survey networks.
A GNSS epoch is a specific moment in time at which a Global Navigation Satellite System receiver collects and records positioning measurements from satellites.
Radio frequency bands used by Global Navigation Satellite Systems (GNSS) to transmit positioning signals, with L1 at 1575.42 MHz, L2 at 1227.60 MHz, and L5 at 1176.45 MHz.
Multipath is the degradation of GNSS signal accuracy caused by reflected satellite signals arriving at the receiver antenna after bouncing off nearby surfaces.
GNSS signal processing refers to the computational techniques used to receive, decode, and analyze satellite navigation signals to determine precise position, velocity, and time information.
A satellite-based navigation system that determines precise three-dimensional coordinates (latitude, longitude, and altitude) of survey points anywhere on Earth.
GPS Week is a continuous count of weeks since January 6, 1980, used as the fundamental time reference in the Global Positioning System and critical for synchronizing surveying measurements and GNSS data processing.
Grade control is the surveying process of establishing and monitoring elevation references to ensure construction elements are built to specified vertical heights and slopes.
Ground point filtering is a data processing technique that removes non-ground points from LiDAR or photogrammetric point clouds to isolate terrain elevation data for surveying applications.
The Geodetic Reference System 1980 (GRS80) is a standardized mathematical model of Earth's shape used as the basis for global geodetic datums and coordinate systems in modern surveying and mapping.
Ground Sample Distance (GSD) is the distance on the ground between the center of adjacent pixels in an aerial or satellite image, measured in units such as centimeters or meters.
HDOP is a dimensionless factor that describes the geometric strength of satellite positions and their effect on the accuracy of horizontal positioning in GNSS surveying.
A dynamic correction system that compensates for vessel or platform motion in three axes to maintain accurate positioning and data collection during hydrographic and marine surveying operations.
A horizontal angle is the angular measurement between two lines or directions in a horizontal plane, typically measured from a point of observation to establish position and direction in surveying work.
A measurement of the horizontal angle between a reference direction and a target point, obtained by reading the graduated horizontal circle on a surveying instrument.
A reference surface or vertical baseline established for measuring water depths and elevations in maritime and coastal surveying operations.
A hydrographic survey is the systematic measurement and mapping of underwater and coastal water features, including depths, seafloor characteristics, and navigational hazards.
ICP is an algorithm that automatically registers and aligns three-dimensional point clouds by iteratively finding the closest point pairs between datasets to minimize spatial differences.
A computational algorithm that automatically aligns two three-dimensional point clouds by iteratively minimizing the distance between corresponding points.
Industry Foundation Classes (IFC) is an open, neutral data format standard for sharing building information models across multiple disciplines including surveying, architecture, engineering, and construction.
An open, international standard data model for representing building and infrastructure information that enables interoperability between different software platforms used in surveying and construction.
The International Hydrographic Organization's comprehensive standards and specifications for hydrographic surveys, data collection, and nautical chart production worldwide.
Image overlap is the percentage of common ground area visible in two consecutive photographs or images used in photogrammetry and aerial surveying.
Instrument calibration is the systematic process of comparing and adjusting surveying equipment measurements against known standards to ensure accuracy and reliability in field operations.
A protective container specifically designed to transport, store, and safeguard surveying instruments during field operations and between job sites.
The process of determining the correct integer number of wavelengths in GNSS carrier phase measurements to achieve centimeter-level positioning accuracy.
A surveying method that determines the position of a point by measuring angles from two or more known reference stations to establish precise horizontal or vertical location.
A mathematical technique in GNSS surveying that eliminates ionospheric delays by combining dual-frequency signals to improve positioning accuracy.
The propagation delay of electromagnetic signals passing through the ionosphere, caused by free electrons that reduce signal velocity below the speed of light.
ISO 17123 is an international standard that establishes testing procedures and accuracy requirements for surveying instruments to ensure consistent measurement performance and data quality across projects.
An international standard that establishes information management procedures and processes for building information modeling across the full lifecycle of construction and infrastructure projects.
A real-time positioning technique using GNSS receivers in motion to determine precise coordinates by continuously tracking satellite signals and applying corrections.
KML (Keyhole Markup Language) and KMZ (compressed KML) are XML-based file formats used to display geographic data and survey measurements in mapping and geospatial applications.
A conformal map projection that uses a cone tangent or secant to the Earth's surface, minimizing distortion over mid-latitude regions and preserving angles while maintaining relative accuracy for surveying and mapping applications.
A legal survey that establishes property boundaries and ownership limits to create or verify land title documents for real estate transactions.