Surveying Glossary — Letter G

Galileo is the European Union's global navigation satellite system providing positioning, navigation, and timing services with high precision and integrity for surveying and mapping applications.

A precisely surveyed location on the earth's surface used as a reference point for mapping, photogrammetry, and geospatial data collection.

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.