Extension/Outreach: Glossary of Terms

Precision Agriculture Glossary

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A B C D F G I   L M N O P R S T U V Y


AB Line - An imaginary reference line set for each field that a tractor/sprayer guidance system to follow. There are different reference lines that can be set in a field to fit a particular geography or layout.

Agronomic Data - Represents data compiled from a specific farming operation or at the field level generally related to agronomy based information such as yield, population, hybrid, nutrient application.  Agronomic Data is tied to the land or field where it was generated.  Types of Agronomic Data include (but are not limited to) hybrid selections, plant populations, yield data, soils data, pesticide application details, and scouting information.  Data generated from a yield monitor can be used to document yields, and for on-farm seed trials. In addition, yield monitor data can be used to make genetic, environmental, and management effect analyses. Soils data is being used to make fertilizer and regional environmental compliance decisions, while scouting data is being used to make spraying decisions as well as regional pest or disease analytics.

As-Applied Map - Is a map containing site-specific information about the location and rate of application for fertilizer or chemical input. Usually created with a GPS equipped applicator and data logger.

Automatic Section Control - Turns application equipment OFF in areas that have been previously covered, or ON and OFF at headland turns, point rows, terraces, and/or no-spray zones such as grass waterways. Sections of a boom or planter or individual nozzles/rows may be controlled.

Autonomous Operation - Vehicle guidance without the need for human intervention. A tractor may be driven by a series of on-boards sensors and GPS for precision driving without damage to crops.

Auto-Steer - A GPS guidance system that steers agricultural equipment with centimeter accuracy. This level of accuracy requires real time kinematic (RTK) correction of GPS signals. Auto-steer is an add-on component for equipment. It includes both the GPS system to receive and process the signals, software and hardware to allow the input of control maps and the mechanical equipment to actually steer the tractor. Some new tractors are available “auto-steer ready.”

Auto Swath - GPS machine control systems that include boom control and planter control by row sections or individual row.


Base Station - The RTK-GPS receiver and radio that are placed in a stationary position, functioning as the corrections source for roving tractor units in an area. These stations can be either portable or permanently installed systems and their coverage can range from 5 to 10 miles depending on topographic conditions, antenna height, and radio-transmit power.  Also called a reference station, is a receiver located at a surveyed benchmark. The base station calculates the error for each satellite and through differential correction, improves the accuracy of GPS positions collected at unknown locations by a roving GPS receiver. 

Baud Rate - Rate at which information is transferred in a communication channel. Refers to the number of signal or symbol changes that occur per second. Higher baud rates have more bits per second transferred.


CAN-Bus (in tractors and implements) - CAN-Bus is a high-speed, wired data network connection between electronic devices. The hardware/wiring of CAN-Bus networks are generally the same, while the protocols for communication can be different and vary depending on the industry where they are used. These networks are used to link multiple sensors to an electronic controller, which can be linked to relays or other devices on a single set of wires. This reduces the amount of wires needed for a system and allows for a cleaner way to connect additional devices as system demands change.

Compact Measurement Record (CMR) - Survey grade communication & differential corrections.  There are three different forms (CMR, CMR+, and CMRx) and the difference between them is the amount of correction data that can be obtained due to the amount of satellites.  It’s common to see this term using Trimble GPS systems.

Coordinate System - Used in GPS/GNSS navigational systems to reference locations on Earth. There are many coordinate systems but frequently used ones include: latitude and longitude, Universal Transverse Mercator (UTM), and State Plane coordinate systems.

Continuously Operating Reference Station (CORS) [Network] - A network managed by the U.S. office of National Ocean Service (NOAA) to provide GNSS data consisting of carrier phase measurements throughout the United States.  CORS eliminates the need for producers to purchase a personal base station, thereby lowering investment costs for RTK applications, and initial research has indicated that CORS can provide RTK-level correction within a 20 mile radius of the station’s location. Because CORS data is transmitted over the internet there are no line of sight requirements as with radio transmitted signals.

Crop Sensors - Optical crop sensors used to measure and/or quantify crop health or evaluate crop conditions by shining light of specific wavelengths at crop leaves, and measuring the type and intensity of the light wavelengths reflected back to the sensors.


Differential Global Positioning System (DGPS) - A method of using GPS which attains the position accuracy needed for precision farming through differential correction.

Differential Correction - Correction of a GPS signal that is used to improve its accuracy (to less than 100 m/~330 ft) by using a stationary GPS receiver whose location is known. A second receiver computes the error in signal by comparing the true distance from the satellites to the GPS measured distance. 

Digital Elevation Model (DEM) - A digital representation of a surface, used for topography.

Dilution Of Precision (DOP) - One of many quality measurements to evaluate solutions derived by a positioning receiver. This is a numeric value that relates relative geometries between positioning satellites as well as the geometries between the satellites and the receiver; the lower the value, the higher the probability of accuracy. DOP can be further classified to other variables: GDOP (three-dimensional position plus clock offset), HDOP (horizontal position), PDOP (three-dimensional position), TDOP (clock offset), and VDOP (vertical position). A DOP value of 4 or less is typically desired for best accuracy.

Directed Sampling - Simple technique of incorporating prior knowledge about soil variability into the sampling design to match sampling distribution and intensity with known soil patterns.


Fix - A single position calculated by a GPS receiver with latitude, longitude, altitude, time, and date.


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.

GLONASS (GLObal'naya NAvigatsionnaya Sputnikovaya Sistema) - The satellite-navigation network maintained by the Russian government. The English translation of this name is “GLObal NAvigation Satellite System,” or more commonly named “GLONASS.” Utilizing GLONASS enabled receivers for precision ag applications provides additional satellite coverage and often improved performance of guidance systems. See also GNSS. Russian version of the American GPS satellite system. It is a radio-based satellite navigation system operated for the Russian government by the Russian Space Forces with a constellation of 24 operational satellites in 2010.

Global Navigation Satellite System (GNSS) - Refers to using multiple satellite navigation systems concurrently by a GPS receiver to compute its position. What makes a GNSS receiver superior to a GPS receiver is its capabilities of receiving 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.

GNSS Receiver - A computer-radio device that receives satellite information by radio waves to determine the position of the antenna relative to 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.

Grid Soil Sampling - Laying a grid over a map of a field and taking soil samples at the middle of each grid on the map. May be done at much higher densities (up to 42 samples per acre) to approximate the true spatial variability of a number of soil nutrient levels.

Ground Sampling Distance (GSD) - 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 to a designated target, as well as desired changes in velocity, rotation and acceleration for following that path.  There are two basic categories of guidance products: 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 correction 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.


Industrial Internet - A term coined by Frost & Sullivan and refers to the integration of complex physical machinery with networked sensors and software. The industrial Internet draws together fields such as machine learning, big data, the Internet of things, machine-to-machine communication and Cyber-physical system to ingest data from machines, analyze it (often in real-time), and use it to adjust operations.  Some consider the evolution of digital agriculture today (e.g. 2015) as leading to the Industrial Internet in agriculture.

Internet of Things - The network of physical objects or "things" embedded with electronics, software, sensors, and network connectivity, which enables these objects to collect and exchange data. The Internet of Things (IoT) allows objects to be sensed and controlled remotely across existing network infrastructure, creating opportunities for more direct integration between the physical world and computer-based systems, and resulting in improved efficiency, accuracy and economic benefit. Each thing is uniquely identifiable through its embedded computing system but is able to interoperate within the existing Internet infrastructure. Experts estimate that the IoT will consist of almost 50 billion objects by 2020.

ISOBUS - ISOBUS standard 11783 is a communication protocol for the agricultural industry that is used to specify a serial data network for control and communications on forestry or agricultural tractors and implements. ISOBUS-compliant tractors and implements come with round 9-pin connectors.


LANDSAT (LAND SATellite) - A series of U.S. satellites used to study the earth’s surface using remote sensing techniques.

Lightbar - Is a navigation tool coupled with a GPS designed to keep the driver on-course. Applications include planting and fertilizer applications to reduce skips and overlaps. Typically, guidance is provided through a series of LED lights.

Latitude - A north/south measurement of position perpendicular to the earth's polar axis.

Longitude - An east/west measurement of position in relation to the Prime Meridian, an imaginary circle that passes through the north and south poles.


Machine Data - Data that is compiled using multiple sensors located on agricultural machinery.  Most relate machine data to the information that can be collected from the CAN (controlled area network) on machines and implements. Machine data can also include guidance system information (autosteer, GPS path files, bearing, etc.), variable rate control/technology and seeding rate controllers.  Data in these forms is transmitted to Agricultural Technical Providers (ATPs) via CANBus, which is a high-speed, wired data network connection between devices.  This device utilizes a single wire set to relay information, which reduces the amount of wires needed for a system and allows for a cleaner way to transfer data.

Management Zone - Management zones are created by subdividing a field into 10-20 acre areas with similar characteristics. Yield maps, soil texture maps, elevation data, EC data, sensor data and farmer knowledge can be used to create management zones in GIS software. There are several methods available for creating management zones.

Mass Flow Sensor - Is a sensor that measures grain flow in a yield monitor system.

Moisture Sensor - Is a sensor that measures grain moisture in a yield monitor system.


National Marine Electronics Association (NMEA) - Set communications standards for GPS data.

Near Infrared (NIR) - Near infrared (red), green (blue), red (green) is useful in seeing changes in plant health.

NDVI - Normalized Difference Vegetation Index is the ratio of the difference between the red and near-infrared bands divided by their sum used to identify and enhance the vegetation contribution in a digital remote sensing analysis; a simple graphical indicator that can be used to analyze remote sensing measurements and assess whether the target being observed contains live green vegetation or not.

NAVSTAR (NAVigation by Satellite Timing and Ranging) - The U.S. based global navigation satellite system that was funded by taxpayers and controlled by the DOD.


OmniSTAR - A subscription based differential GPS source. Omnistar is a satellite-based DGPS source that requires a special GPS antenna.


Precision Agriculture - Precision agriculture is a farming management concept based on observing, measuring and responding to variability in crops. These variabilities contain many components that can be difficult to compute and as a result technology has advanced to off-set these difficulties.  Two types of technology can generally be found within precision agriculture: those which ensure accuracy, and those that are meant to enhance farming operations.  By combining these two technologies, farmers are able to create a decision support system for an entire operation, thereby maximizing profits and minimizing excessive resource use. This may include managing crop production inputs (seed, fertilizer, lime, pesticides, etc.) on a site-specific basis to increase profits, reduce waste and maintain environmental quality.

Prescribed Application - The dispensing of a material or chemical into the field on a prescribed or predetermined basis. A prescription map is generated by an expert (grower and/or agronomist) based on information about the field in use before an application. The prescription determines how much of something will be applied.

Prescription Map - A prescription map tells the controller how much product to apply based on the location of the equipment in the field.


Rate Controller - An electronic device that varies the amount of chemical/plant nutrient applied to a given area.

Remote Sensing - The act of detection and/or identification of an object, series of objects, or landscape without having the sensor in direct contact with the object. The most common forms include color and color infrared aerial photography, satellite imaging and radar sensing.

Real-Time Correction - correction of a GPS signal by simultaneously transmitting the differential correction information to a mobile receiver.

Real-Time Kinematic (RTK) - Real-Time Kinematic is a high-end GPS capable of centimeter level positional accuracy. A procedure whereby carrier-phase corrections are transmitted in real time from a reference receiver to the user’s receiver. Depending on local availability, RTK corrections can be delivered by radio modem from an on-site base station or a state’s CORS network, or even over the internet using Wi-Fi.


Site Specific Crop Management (SSCM) - The use of yield maps, grid sampling and other precision tools to manage the variability of soil and crop parameters and aid decisions on production inputs (also referred to as Precision Farming)

Sensor Technologies - Sensor technology refers to on-the-go optical sensors used to measure crop status. These sensors utilize an active LED light source to measure NDVI (Normalized Difference Vegetative Index) to predict crop yield potential. NDVI values reflect the health or “greenness” of a crop and can also provide a relative biomass measurement. Data collected from these sensors are being used to direct variable rate nitrogen applications in grain crops and plant growth regulator and defoliants in cotton.

Shortwave Infrared (SIR) – Shortwave infrared (red), near infrared (green), and green (blue) used to show flooding or newly burned land.

SSURGO (Soil SURvey GeOgraphic) Database - A digital version of the NRCS soil books. Each soil type is represented as a polygon and tied with associated soil type properties.


Terrain Compensation - An add-on feature for auto-guidance systems which correct position error that may occur when equipment travels over rolling terrain. Roll, pitch and yaw are commonly referred to when discussing terrain compensation. Roll refers to the change in elevation between the left and right sides of the vehicle; pitch refers to the change in elevation between the front and rear of the vehicle; and yaw refers to any sliding or turning motion of the vehicle to the left of right.

Thermal Infrared (TIR) - Shown in gray tones to illustrate temperature. It measures radiation from the plant and soil surface.


Universal Transverse Mercator (UTM) -  Coordinate system that represents the earth’s spherical shape as 2-D zones that are evenly spaced grid lines.

Unmanned Aerial Vehicle (UAV) - An unmanned aerial vehicle (UAV), commonly known as a drone and also referred by several other names, is an aircraft without a human pilot aboard. The flight of UAVs may be controlled either autonomously by onboard computers or by the remote control of a pilot on the ground or in another vehicle. In agriculture, UAVs are typically used to survey crops. The available two types of UAVs – fixed-wing and rotary-wing – are both equipped with cameras and are guided by GPS. They can travel along a fixed flight path or be controlled remotely.


Variable Rate Technology (VRT) - GPS and precise placement technology that uses an "application guidance" map to direct the application of a product to a specific, identifiable location within a field. Instrumentation such as a variable-rate controller for varying the rates of application of fertilizer, pesticides and seed as one travels across a field. VRT consists of the machines and systems for applying a desired rate of crop production materials at a specific time (and, by implication, a specific location); a system of sensors, controllers and agricultural machinery used to perform variable-rate applications of crop production inputs; refers to a system that varies the rate of agricultural inputs such as seed, fertilizer, and crop protection chemicals in response to changing local conditions.

Vegetation Index(VI) - A ratio created by dividing the red by the near-infrared spectral bands used to identify and enhance the vegetation contribution in a digital remote sensing analysis.

Variable Rate Application (VRA) - Adjustment of the amount of crop input such as seed, fertilizer, lime or pesticides to match conditions (yield potential) in a field.


Yield Calibration - Procedures used to calibrate a yield monitor for specific harvest conditions such as grain type, grain flow, and grain moisture.

Yield Mapping - Is a yield monitor coupled with a GPS. Each yield reading is tagged with a latitude and longitude coordinates, which is then used to produce a yield map. Refers to the process of collecting geo-referenced data on crop yield and characteristics, such as moisture content, while the crop is being harvested.

Yield Monitor - A yield-measuring device installed on harvest machines. Yield monitors measure grain flow, grain moisture, and other parameters for real-time information relating to field productivity.


(Definitions from AgGlossary, PrecisionAg, University of Nebraska Lincoln, Alabama Cooperative Extension System)