# Appendix ## Glossary of terms #### Aerotriangulation *Aerotriangulation* is a photogrammetric method of determining the geometric properties of objects from photographic images, especially for mapping and modeling purposes. *** #### Antenna Phase Center The point in an antenna where the GNSS signal is considered to be received, crucial for precise positioning calculations. *** #### 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. *** #### Baseline In GNSS surveying, the vector distance between two GNSS receivers simultaneously tracking the same satellites. *** #### BeiDou A global navigation satellite system developed and operated by China, providing positioning, navigation, and timing services. *** #### 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 that 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, typically used in reference to 3D modeling of physical objects. *** #### Cloud Point A set of data points in space produced by 3D scanners or photogrammetry, representing the external surface of an object or terrain. *** #### Control Point A point on the ground with known coordinates used to georeference and align spatial data accurately. *** #### CORS **Continuously Operating Reference Stations** are networks of GNSS receivers that provide real-time correction data and support high-accuracy positioning. *** #### DEM A **Digital Elevation Model** is a 3D representation of a terrain's surface created from terrain elevation data, excluding objects like buildings and vegetation. *** #### DOP (Dilution of Precision) An indicator of the quality of a GNSS position considering the geometry of the satellite constellation relative to the GNSS receiver. A low DOP value is preferred. Common DOP types are: * **GDOP** - *Geometric Dilution of Precision* considers the combination of vertical, horizontal, time, and position errors. * **HDOP** - *Horizontal Dilution of Precision* represents the effect of satellite geometry on horizontal position accuracy. * **PDOP** - *Position Dilution of Precision* combines the horizontal and vertical DOP. * **RDOP** - *Relative Dilution of Precision* measures the relative positional error between two receivers. * **TDOP** - *Time Dilution of Precision* represents the effect of satellite geometry on time determination accuracy. * **VDOP** - *Vertical Dilution of Precision* represents the effect of satellite geometry on vertical position accuracy. *** #### DSM A **Digital Surface Model** is a 3D representation of the Earth's surface, including all objects on it, such as buildings, trees, and other structures. *** #### DTM A **Digital Terrain Model** is similar to a DEM but includes additional terrain attributes, such as break lines and mass points, to represent the ground surface more accurately. *** #### ECEF **Earth-Centered, Earth-Fixed** is a Cartesian coordinate system used by the WGS‑84 reference frame. In this coordinate system, the origin is at the Earth's center of mass. *** #### EGNOS **European Geostationary Navigation Overlay Service** is a regional satellite-based augmentation system that improves the accuracy of GNSS signals over Europe. *** #### Ellipsoid A mathematically defined surface that approximates the shape of the Earth, used as a reference in geodesy and map projections. *** #### Ephemeris Data Information about the positions and velocities of GNSS satellites, used by receivers to calculate accurate positions. *** #### Fixed Solution Indicates that the integer ambiguities have been resolved, providing the most precise type of solution available in an RTK GPS application. *** #### Float Solution Indicates that the integer ambiguities have not been resolved, resulting in positional accuracy less than that of a fixed solution. *** #### Galileo A global navigation satellite system controlled by the European Union. *** #### GCP (Ground Control Point) An 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. *** #### Geocoding The process of converting addresses or other location descriptors into geographic coordinates. *** #### Geodatabase A database designed to store, query, and manipulate geographic information and spatial data. *** #### Geodetic Datum A coordinate system and reference points used to locate places on the Earth, serving as a foundation for mapping and surveying. *** #### Geoid The hypothetical shape of the Earth, coinciding with mean sea level, used as a reference surface from which to measure elevations. *** #### Georeferencing The process of assigning real-world coordinates to each pixel of a raster image or vector dataset, aligning spatial data to a known coordinate system. *** #### GIS A **Geographic Information System** is a system that collects, stores, analyzes, and displays geographically referenced information. *** #### GLONASS **Global Navigation Satellite System** is the 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** is the GNSS controlled by the U.S. government. *** #### GSD **Ground Sampling Distance** is the distance between pixel centers measured on the ground, representing the spatial resolution of an aerial image. *** #### HDOP **Horizontal Dilution of Precision** represents the effect of satellite geometry on horizontal position accuracy. *** #### IMU An **Inertial Measurement Unit** is a 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 and gyroscopes. *** #### Kinematic Surveying A method of surveying where the GNSS receiver is in motion, allowing for rapid data collection over large areas. *** #### 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. *** #### LiDAR **Light Detection and Ranging** is a remote sensing method that uses laser pulses to measure distances to the Earth's surface, generating precise, three-dimensional information about the shape of the Earth and its surface characteristics. *** #### Map Projection A systematic transformation of latitudes and longitudes from the Earth's curved surface onto a flat plane. *** #### Multipath An error in GNSS signal reception caused by signals reflecting off surfaces before reaching the receiver, leading to inaccuracies. *** #### NAD83 **North American Datum 1983** is a geocentric datum and reference system used for geodetic control in North America. *** #### NMEA The **National Marine Electronics Association** defines a standard data format for interfacing marine electronic devices, commonly used by GNSS receivers to transmit data. *** #### NTRIP **Networked Transport of RTCM via Internet Protocol** is a standard method for RTK GPS rovers and base stations to exchange correction data over the internet. *** #### OPUS **Online Positioning User Service** provides free post-processing of GPS base data into high-accuracy National Spatial Reference System coordinates. *** #### Orthomosaic An orthomosaic is a geometrically corrected and georeferenced aerial image composed of multiple photographs stitched together to create a seamless and accurate map. *** #### PDOP **Position Dilution of Precision** combines the effects of HDOP and VDOP to represent the effect of satellite geometry on three-dimensional position accuracy. *** #### Photogrammetric Tie Point Points identified on overlapping images used to stitch images together in photogrammetry, ensuring accurate alignment. *** #### Photogrammetry The science of making measurements from photographs, especially for recovering the exact positions of surface points. *** #### PPK **Post-Processed Kinematic** is a GPS correction technique where the correction calculations are performed after data collection, rather than in real-time like RTK. *** #### PPP **Precise Point Positioning** is a GNSS data processing technique that provides highly accurate position solutions without the need for a local reference station. *** #### Precision A measure of how closely repeated measurements or observations under unchanged conditions show the same results, indicating the repeatability of one or a set of measurements. *** #### RDOP **Relative Dilution of Precision** measures the relative positional error between two receivers. *** #### RINEX **Receiver Independent Exchange Format** is a file format that is commonly used to interchange raw satellite navigation system data. *** #### Rover In GNSS surveying, a mobile receiver unit that collects data while moving, receiving corrections from a base station or network. *** #### RTCM **Radio Technical Commission for Maritime Services** defines the RTCM protocol that high-precision 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. *** #### RTN **Real-Time Network** is a network of GNSS reference stations that provide real-time corrections over a wide area, enhancing positioning accuracy for rovers. *** #### Satellite Observation A recording of satellite signals made using GNSS receivers for later processing. *** #### SBAS **Satellite-Based Augmentation System** enhances GNSS signals by providing correction messages, improving accuracy, integrity, and availability. *** #### SBET **Smoothed Best Estimate of Trajectory** is data output from inertial measurement units (IMUs) combined with GNSS data to provide accurate position and orientation information. *** #### SfM **Structure from Motion** is a photogrammetric technique that reconstructs 3D structures from 2D image sequences by estimating camera positions and orientations. *** #### SNR **Signal-to-Noise Ratio** is a measure of signal strength relative to background noise, important in assessing the quality of GNSS signals. *** #### Static Surveying A surveying technique where the GNSS receiver remains stationary for a period, providing high-precision position data. *** #### TDOP **Time Dilution of Precision** represents the effect of satellite geometry on time determination accuracy. *** #### Transformation The mathematical process of converting coordinates from one coordinate system to another. *** #### Tropospheric Delay The slowing of GNSS signals as they pass through the Earth's troposphere, causing delays that can affect positioning accuracy. *** #### UAV An **Unmanned Aerial Vehicle** is an aircraft without a human pilot onboard. In surveying and mapping, UAVs are often used to collect aerial imagery and data for analysis. *** #### UTM **Universal Transverse Mercator** is a coordinate system that divides the world into a series of six-degree longitudinal zones, allowing for detailed mapping. *** #### VDOP **Vertical Dilution of Precision** represents the effect of satellite geometry on vertical position accuracy. *** #### WGS‑84 **World Geodetic System 1984** is the mathematical ellipsoid used by GPS since January 1987. *** #### WMS **Web Map Service** is a standard protocol for serving georeferenced map images over the internet.