Precision Agriculture
Glossary
G
GEOGRAPHIC COORDINATE SYSTEM. A reference system using latitude and longitude to define the locations of points on the surface of a sphere or spheroid.
GEOGRAPHIC INFORMATION SYSTEM (GIS). A computer-based system that is capable of collecting, managing, and analyzing geographic spatial data. This capability includes storing and utilizing maps, displaying the results of data queries, and conducting spatial analysis. GIS is usually composed of map-like spatial representations called layers, which contain information on a number of attributes such as elevation, land ownership and use, crop yield, and soil nutrient levels.
GEOREFERENCING. The process of adding geographic data to yield data or other field attributes either in real-time (on-the-go) or by post-processing or the process of associating data points with specific locations on the Earth’s surface.
GLOBAL NAVIGATION SATELLITE SYSTEM (GNSS). This refers to using multiple satellite navigation systems concurrently by a GPS receiver to compute their position. What makes a GNSS receiver superior to a GPS receiver is its capability to receive signals from navigational satellites other than, and in addition to, those that are of the GPS network. There are two operational satellite navigation systems at this time: The United States of America’s GPS and Russia’s GLONASS.
GLOBAL POSITIONING SYSTEM (GPS). A system using satellite signals (radio waves) to locate and track the position of a receiver/antenna on the Earth. GPS is a technology that originated in the U.S. The U.S. government currently maintains it, and is available to users worldwide free of charge. There are 30 satellites in the GPS constellation.
GNSS RECEIVER. A computer-radio device that receives satellite information by radio waves to determine the position of the antenna relative to the Earth’s surface.
GNSS SATELLITE. A communication vehicle that orbits the Earth. Satellites send time-stamped signals to GPS or GNSS receivers to determine positions on Earth.
GROUND CONTROL POINTS. Stationary objects/areas on the Earth’s surface that provide georeferenced points in a remote sensing image/aerial photograph.
GROUND SAMPLING DISTANCE (GSD). The pixel size of remotely sensed imagery. Example: 30-meter, 1-meter, 20-centimeters.
GUIDANCE. The determination of the desired path of travel (the “trajectory”) from the vehicle’s current location ta designated target, as well as desired changes in velocity, rotation, and acceleration for following that path. Two basic categories of guidance products are lightbar/visual guidance and auto guidance. For lightbar/visual guidance, the operator responds to visual cues to steer the equipment based on positional information provided by a GPS. For auto-guidance, the driver makes the initial steering decisions and turns the equipment toward the following pass prior to engaging the auto-guidance mechanism. Auto-guidance can use differential corrections such as WAAS, subscription services, and RTK. RTK is the most accurate level of auto-guidance available, typically +/- 1 inch. Benefits include improved field efficiency, reduced overlap of pesticide applications, time management, and reduced driver fatigue. See also WAAS, Subscription Correction Signal, and RTK.
