GEOG 3315 - Module 8

Global Navigation Satellite System (GNSS): A satellite-based positioning system composed of three components, providing continuous, worldwide positioning. Examples include NAVSTAR GPS (USA) and GLONASS (Russia). 

NAVSTAR GPS: A GNSS system created by the United States, providing worldwide, continuous, accurate, three-dimensional position and velocity, and precise time. 

Space Segment: Part of the GPS system consisting of a constellation of satellites orbiting Earth, ensuring at least four satellites are visible above the horizon at all times. 

Control Segment: Earth-based monitoring stations that track, update, and calibrate the clocks on GPS satellites. The master station is located in Colorado. 

User Segment: Composed of individuals using GPS receivers, which gather information from satellites to calculate positions. 

Coarse Acquisition Code: A code broadcasted by GPS satellites used by both civilian and military sectors, providing pseudorandom code describing ephemeris data and GPS almanac. 

P Code: A code used to determine the location of the GPS receiver, broadcasted over seven days, used by the civilian sector. 

Ephemeris Data: Information about the location of satellites, essential for determining positions using GPS. 

Differential GPS (DGPS): A method to increase the accuracy of GPS by using a base station at a known location to broadcast corrections to a rover receiver. 

Real-Time Kinematic (RTK) GPS: A differential GPS method where corrections are broadcasted in real-time using communication capabilities like radio. 

Post-Processing: Applying GPS base station corrections to rover data at a later time using a computer, suitable for most situations without requiring real-time communication. 

Continuous Operation Reference Stations (CORS): A network of base stations providing real-time or post-processing GPS observations, established by the United States Coast Guard. 

Wide Area Augmentation System (WAAS): A differential positioning method using geostationary satellites and a network of reference stations to provide real-time accuracies within 7 meters or less. 

Multipath Error: An error occurring when the GPS signal travels a longer distance due to bouncing off objects like buildings or trees before reaching the receiver. 

Dilution of Precision (DOP): A measure of the GPS satellite constellation geometry's effect on positional accuracy, with lower values indicating better accuracy. 

Positional DOP (PDOP): The ratio of the volume of a tetrahedron created by the most widespread satellites to the volume of an ideal tetrahedron, used to assess overall positional accuracy. 

Ephemeris Error: The residual error in the satellite's exact position compared to its reported position, affecting position calculations. 

Atmospheric Error: Variations in the speed of light as the GPS signal travels through the Earth's atmosphere, affecting distance calculations. 

Clock Error: Discrepancies between the atomic clocks in GPS satellites and the less precise clocks in GPS receivers, affecting temporal calculations and positioning. 

Field Data Collection: The process of gathering data in the field using devices like GPS receivers or smart devices with GNSS chips, often integrated with mobile mapping software.