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The GPS Surveying Glossary

Updated: May 4, 2022

Base Station - A base station is a GNSS antenna and receiver set up as a reference specifically to collect data to be used in determining precise rover positions.

BIM - Building information modeling is a process involving the generation and management of digital representations of the physical characteristics of sites.

BIMs - Building Information Models are digital models which support decision-making regarding a built asset.

CAD - Computer-aided Design is the use of computers in the creation, modification, analysis, or optimization of a design. CAD is typically used in reference to 3D modeling of physical objects.

DOP - Dilution of Precision is an indicator of the quality of a GNSS position considering the location of each satellite relative to other satellites in the constellation, as well as their geometry relative to the GNSS receiver. A low DOP value is preferred. Common DOPs for GNSS applications are:

– PDOP – Position

– GDOP – Geometric

– RDOP – Relative

– HDOP – Horizontal

– VDOP – Vertical

– TDOP – Time

ECEF - Earth‑Centered, Earth‑Fixed is a cartesian coordinate system used by the WGS‑84 reference frame. In this coordinate system, the center of the system is at the earth's center of mass.

Fixed Solution - Indicates that the integer ambiguities have been resolved. This is the most precise type of solution available in an RTK GPS application.

Float Solution - Indicates that the integer ambiguities have not been resolved the resulting positional accuracy is less than that of a fixed solution.

Galileo - is a global navigation satellite system controlled by the European Union.

GCP - A ground control point is a easily identifiable point on the ground that can be used as a reference for measurements. Ground control points are often used in surveying and photogrammetry to provide a known reference point for measurements.

GIS - Geographic Information System is a system that collects, stores analyzes, and displays geographically referenced information.

GLONASS - GLObal NAvigation Satellite System is the global navigation satellite system (GNSS) controlled by the Russian government.

GNSS - Global Navigation Satellite System is the standard generic term for satellite navigation systems that provide geospatial positioning with global coverage.

GPS - Global Positioning System (GPS) is the global navigation satellite system (GNSS) controlled by the U.S. government.

OPUS - Online Positioning User Service provides free post-processing of GPS Base data into high-accuracy National Spatial Reference System coordinates.

RINEX - Receiver Independent Exchange Format is a file format that is commonly used to interchange raw satellite navigation system data.

L1 - The primary L‑band carrier used by GNSS satellites to transmit satellite data on the 1575.42 MHz frequency.

L2 - The secondary L‑band carrier used by GNSS satellites to transmit satellite data on the 1227.6 MHz frequency.

NTRIP - Networked Transport of RTCM via Internet Protocol. NTRIP is a standard method for RTK GPS rovers and base stations to exchange correction data over the internet.

Precision - A measure of how closely random variables tend to cluster around a computed value, which indicates the repeatability of one or a set of measurements.

Photogrammetry - the science of making measurements from photographs.

RTCM - Radio Technical Commission for Maritime Services is a commission that defines the RTCM protocol that high precisions GPS receivers use to exchange correction data.

RTK - Real‑time kinematic is a technique that uses carrier-based ranging to provide ranges to satellites that are much more precise than those available through code-based positioning.

Satellite Observation - A recording of satellite signals made using GNSS receivers for later processing.

WGS‑84 - World Geodetic System (1984), the mathematical ellipsoid used by GPS since January 1987.

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