Active Sensing Systems - Remote sensing systems that generate a signal, bounce the signal off an object, and measure the signal reflected off the object.

Actuator - A device used in variable rate applications that responds to controller signals to regulate the amount of material applied to a specific field.

Aerial Photography - Remote sensing technique in which a photograph of a portion of the Earth's surface is taken from an aircraft or satellite in flight.

Algorithm - Formula that relates sensor input to actuator output.

American Standard Code for Information Interchange (ASCII) - Predominant code used by present-day computers for identifying characters (numbers and letters).

Anti-Spoofing - Process of encrypting the L2 signal to prevent unauthorized transmissions of false GPS signals.

Application - A practical use of computer software, an electronic system, or a concept.

Applications Package - Specialized computer programs and their associated documentation developed for practical usage. Ideally, applications packages allow a non-computer specialist to use the computer without learning complex programming languages.

Arc - A line described by an ordered sequence of points associated with vector data models. When two or more arcs are joined by a node and several arcs are linked together in a loop.

Archive - The storage of a year or more of historical records or data.

Array - Line of sensors that collect a whole line, or swath, or data at one time.

Aspect - Horizontal direction in which a slope faces (e.g., a SE facing slope has an aspect of 135 degrees).

Attribute - A numeric and/or text description of a spatial entity (e.g., address or owner's name for a parcel).

Attribute Value - A value or property that is a characteristic of a spatial element. For example, a specific symbol or color may represent 150-160 bu/A, which is a value assigned to that attribute.

Band - Discrete interval of the electromagnetic spectrum between two wavelengths.

Base Map - Map containing field boundaries and data on significant visible surface features.

Batch Type Yield Monitor - Yield monitor that weighs the amount of harvested grain as it sits in the combine grain tank or as it is being unloaded. Yield must be calculated using an estimate of the area harvested.

Baud Rate - A measure that describes the speed of the transmission of single digital elements over a communication line. The number indicates how rapidly data can move through your modem or between a computer and a printer.

Benchmark - Used to define how comparisons are to be made between different computer software or systems according to specific requirements; or, in surveying, a benchmark is the elevation at a specific point.

Bit - An abbreviated term for binary digit, the smallest unit of computer data.

Block Kriging - A piecewise form of kriging based on grid cells.

Buffer - An area defined by the specified length extended around a point, line, or area.

Byte - A unit of computer storage of binary data usually comprising eight bits, and equivalent to a character.

Calibrated Vegetation Map - Map that presents the vegetation in a field in terms of colors within the Green Vegetation Index. Calibration of the maps allows two different maps to be compared because the resulting scales will be the same on both maps.

Capacitance-Type Sensor - Moisture sensor that measures the dielectric properties of grain as it passes between metal plates.

Carrier - Radio frequency signal on which information is encoded and transmitted.

Carrier Tracking Loop - Module in a GPS receiver that extracts the satellite message by aligning the receiver's internally generated signal with the phase of the received GPS signal. Used to provide a carrier-phase observation.

Carrier-Phrase Tracking - Accurate, sophisticated method of determining position requiring two special receivers that measure small differences in radio signals.

Cartography - Art and science of the organization and communication of geographically related information such as a yield image into maps or charts.

Cation Exchange Capacity (CEC) - Represents the total quantity of negative charge that is available in the soil to attract positively charged ions in the soil solution.

Centroid - Position at the center of a one- or two-dimensional (2D) entity such as a polygon.

Channel - Circuitry necessary for a GPS receiver to receive signals from a single GPS satellite.

Choropleth Map - Thematic map, such as a yield image, where quantitative spatial data is depicted through the use of shading or color variations of yield ranges.

Circular Error Probable (CEP) - A measure of positional accuracy produced by GPS receiver. CEP is radius of the circle inside which the measured position has a 50% probability of being located.

Coarse Acquisition (C/A) Code - Unique code for each GPS satellite. Standard code used by civilian receivers.

Collect-and-Weigh - A method to determine crop yield, typically on a whole field basis. Each truck or wagon load of grain is weighed as it leaves the field and the moisture content is determined by sampling the load.

Computer Aided Mapping (CAM) - Software with the capability of generating standard mapping functions.

Controller - This hardware controls how the application rate is varied. It usually controls a motor or valve that varies the rate of any product.

Contour Line - Line or set of points that represent the same value of an attribute. Commonly used for illustrating lines of the same elevation on a topographic map.

Contouring - Method of interpolation originally used to display elevation changes on a topographic map. Contour lines are lines connecting points to equal elevation or yield.

Control Segment - Portion of GPS consisting of a network on monitoring stations used to update satellite navigation signals.

Crop Scouting - Precise assessments of pest pressure and crop performance that can be tied to a specific location for better interpretation.

Cross Tabulation - Comparison by location of attribute data in two or more map layers.

Database - Collection of files managed as a unit. GIS databases include data about the position and the attributes of geographic features.

Database Management System (DMS) - Collection of software for organizing the information in a database which might contain routines for data input, verification, storage, retrieval, and combination.

Data Ownership - The data is the important thing, not the procedures. There is confusion in agriculture as to who owns the data. Ideally, growers should be the ultimate owners of the data from their fields.

Data Standardization - Process of achieving agreement on common data definitions, representation, and structures to which all data layers must conform.

Dead Reckoning - This positioning system allows you to visually judge your location according to landmarks, terrain, and estimated distances. This system may be accurate enough for some crude mapping programs, but it is generally not adequate for precision agriculture.

Department of Defense (DoD) - Organization responsible for the creation and operation of the Global Positioning System.

Dielectric - Material that sustains an electric field but does not conduct electric current.

Differential Correction - Corrects the GPS signal to make it more accurate. An uncorrected signal will be accurate to within 50 yards. A corrected signal can be accurate to within 5 to 10 feet. To correct the signal, a second GPS receiver is placed in a fixed, known location. This location is used to calculate the current error in the GPS signal. These data are then transmitted to a nearby tractor, combine, or pickup, which corrects its own position.

There are four ways to transmit the correction signal from the base station to the farm implement. One is a dedicated transmitter that is located on an existing tower (Mobile Data, or SATLOC), which has a range of 30 to 40 miles. Another way is to use a separate, private corporation satellite to send the corrected signal (SATLOC), which has a range of 1,000 miles. A third way is to 'piggyback' the correction signal on a commercial FM radio station frequency (DCI, or ACCQPOINT), which also has a range of 30 to 40 miles. The fourth way is to use AGNAV, a new technology that does not need a differential correction.

Differential Global Positioning System (DGPS) - Method of using GPS that improves the position accuracy through differential correction.

Digital Elevation Model (DEM) - Digital representation of the elevation of locations on the land surface. DEM is used in reference to a set of elevation values representing elevations at points in a grid on the Earth's surface.

Digitizer - Table or tablet that has the capability of digitally recording relative position of a cursor which is moved over an area or line.

Digital Line Graph (DLG) - U. S. Geological Survey digital map format used to distribute topographical maps in vector form.

Electro-Optical Sensors - Light sensitive electronic detectors that create an electrical signal proportional to the amount of electromagnetic energy that hits them.

Electromagnetic Energy - Energy that is reflected or emitted from objects in the form of electrical and magnetic waves that can travel through space.

Electromagnetic Spectrum - All wavelengths of electromagnetic energy, including x-rays, ultraviolet rays, visible light, infrared light, and radio waves.

End of Pass Delay - Delay that allows any grain that passes by a yield monitor flow sensor after the combine header has been raised to be included in yield calculations.

Enhanced Vegetation Map - Map that accentuates the small variations in the color of the crop canopy. Two enhanced vegetation maps cannot be compared because the scales on each map will differ.

Enhance Thematic Mapper (ETM) - Device that senses multispectral bands at spatial resolution of 98 feet, a short wave thermal band at a resolution of 394 feet, multispectral thermal bands at a resolution of 197 feet, and a panchromatic band at a resolution of 49 feet. The ETM is scheduled to be used on LANDSAT-7.

Extrapolation - Method to extend data or inferences from known location to another location for which values are not known.

Feature - Geographic component of the Earth's surface that has both spatial and attribute data associated with it.

Federal Communications Commission (FCC) - Government agency that is responsible for enforcing communication standards and frequency band usage.

Field - Set of alphanumeric characters comprising a unit of information; or, location in a data record in which a unit of information is stored.

Flagging - This is the process of establishing grids in a field. A person drives over the field and puts a flag at the location where the sample is to be taken. As GPS becomes more available, the need to make a separate trip over the field to mark spots may be reduced.

Flow Sensor - Sensor that measures amount of material flowing through a pipe per unit of time.

Foreign Agricultural Service (FAS) - U. S. Department of Agriculture agency. FAS gathers and disseminates information on agricultural products in the global marketplace.

Frequency Modulation (FM) - Method of transmitting information on radio waves by encoding the information as a change in frequency or number of cycles per second.

Frequency of Coverage - Measure of how often a sensing system can be available to collect data from a particular site on the ground.

Geocode - Code associated with spatial element which describes its location.

Geographic Data (Spatial Data) - Data that contains the attribute being monitored and the spatial location of the attribute.

Geographical Information Systems (GIS) - Software designed to coordinate data gathered at various times and locations into an overall topographical map. This program allows integration of a variety of data to form a detailed picture of a given point in the field. As an example, grid soil test data, soil type, and past yield information can be combined to determine a map to vary the planting rate.

Geometric Correction - Correction to align measured ground control points in a remotely sensed image with ground control points on an established map.

Geometric Dilution of Precision (GDOP) - Term quantifying the effect of satellite geometry (relative positions of several satellites) on the magnitude of error in a GPS position measurement.

Georeferenced Data - Spatial data that pertains to specific locations on the Earth's surface.

Georeferencing - Process of associating data points with specific locations on the Earth's surface.

Georeferencing System - Coordinate system keeping track of specific points on the Earth 's surface.

Geo-Stationary Satellite - Space vehicles in orbit that keeps them over the same location on the Earth at all times.

Global Positioning System (GPS) - Network of satellites that are designed to help determine a radio receiver's position in latitude, longitude, and altitude. GPS is one of many technologies that is used in precision farming.

Green Vegetation Index (GVI) - Absolute scale consisting of 20 ranges used by RESOURCE2l to account for effects of humidity, dust, and sun angle on remotely sensed images.

Grid - Data structure that uses rectangular units or grid cells arranged in rows and columns to represent an area like a field.

Grid Center Method (Grid Point Sampling or Point Sampling) - Soil sampling method where samples are taken from the center of a grid cell.

Grid Mapping - Predetermined locations in a field where soil or plant samples may be obtained for analysis.

Grid Sampling - Soil sampling method where a field is divided into square sections of several acres. Samples are taken from each section and analyzed.

Grid Cell Method - Soil sampling method where samples are taken randomly from within grid cells and combined to provide an average sample for the entire grid.

Ground Control Points - Clearly defined, stationary objects or areas on the Earth's surface that serve as reference points in a remote sensing image.

Ground Truthing - Verification of the accuracy of data by actual field investigation of areas that have been remotely sensed.

Ground Waves - Manner in which low frequency radio signals travel along the curvature of the earth.

Hard Disk - Large capacity, mechanical, magnetic, computer storage device that stores programs and data.

Histograms - Graphs of frequency of occurrence of different ranges of measurement.

Hyperspectral Sensors - Sensors that are capable of measuring electromagnetic energy from hundreds of individual wavelengths simultaneously.

Image Classification - Processing techniques that apply quantitative methods to the values in a digital yield or remotely sensed scene to group pixels with similar digital number values into feature classes or categories.

Impact Plate - Place placed in the path of grain flow in clean grain system of a combine. The force with which the grain strikes the plate is measured and used to estimate grain flow rate.

Instantaneous Field of View (IFOV) - Measure of spatial resolution of scanning-type sensors. IFOV is an area on the ground "seen" by a sensor.

Instantaneous Yield Monitor - Device that continuously measures and records crop yields on-the-go.

Interpolation - Procedure for predicting the unknown values between neighboring known data values.

Inverse Distance Weighting - Interpolation method similar to local average except the samples closer to the desired location have more influence on the estimation than far away samples.

Inosphere - Blanket of electronically charged particles 50 to 250 miles above the Earth.

Kriging (Creeging) - Interpolation technique to obtain statistically unbiased estimates of field characteristics from a set of neighboring points.

L-Band - Segment of radio spectrum ranging in frequency from 1,000 to 2,000 MHz.

Lag - Horizontal distance between two geographic data points. Used to create a semi-variogram.

Land Information System (LIS) - System for describing data about land and its use, ownership, and development.

LAND SATellite (LANDSAT) - Name of U.S. scientific satellites used to study the Earth's surface using remote sensing techniques.

Latitude/Longitude (LAT/LONG) - Coordinate system that identifies a position on earth. Longitude is east to west. Locations are described in units of degrees, minutes, and seconds.

Layer - Logical separation of mapped information representing common data.

Load Cell - Device that converts a force or weight into an electrical signal.

Local Average - An interpolation method where the unknown value is estimated by a simple average of a selected number of points near the desired location.

Location Reference - Referencing data collected by yield monitor, sensor, or other method and relating it to a specific spatial position.

Local Coordinate System - Coordinates are referenced to a known location. Two local coordinate systems will not "line up" on the same map.

Lookup Table - Reference table containing key attribute values which can be linked or related to data usually collected at a specific location.

Map-Based Variable-Rate Application System - System that adjusts product application rate based on information contained in an electronic field map.

Map Projection - Portrayal of geographic features from the curved surface of the earth onto a flat plane.

Merge - Take two or more maps or data sets and combine them into a single coherent map or database.

Minimum Shift Keying (MSK) - Digital coding method used for transmitting differential correction data for use with DGPS.

Mosaic - Process of assembling GIS database files for adjacent areas into a single file.

Multispectral - Capable of detecting electromagnetic radiation from multiple spectral bands at one time.

Multispectral Linear Array (MLA) - Sensor that uses a radiometer to collect data from 16 bands within the visible and NIR wavelengths at a spatial resolution of 33 ft.

Multispectral Scanner - Electromagnetic sensor that collects data in several wavelength bands at one time.

National Agricultural Statistics Service (NASS) - U. S. Department of Agriculture agency. NASS conducts surveys and prepares reports on production and supplies of food and fiber, prices paid and received by farmers, farm labor and wages, and farm aspects of the agricultural industry.

Nearest Neighbor - Interpolation method where the unknown value in set equal to its nearest neighbor.

Network - Group of linked computers that are able to share software, data, and hardware devices; or, geometric or logical arrangement of nodes and interconnecting lines.

Noise - Random variations or error in a data set.

"Not GPS" (NGPS) - System for calculating location of an object by determining distances from at least three land based radio towers.

Output - Product of a computer process and analysis which may be displayed as a computer screen, printed map, or tables of values.

Orthophotograph - Aerial photograph that corrects distortion caused by tilt, curvature, and ground relief.

Panchromatic - Images created from radiation with wavelengths between 0.45 and 0.90 mm.

Parallel Swathing - Driving a vehicle in straight, parallel paths without leaving gaps or overlapping.

Passive Sensing Systems - Remote sensing systems that measure naturally emitted and reflected signals.

PCMCIA Card - Small credit-card-size data storage device used by most yield monitors.

pH - Term used to indicate the degree of acidity of alkalinity of a material. pH level of 7.0 is neutral. pH level above 7.0 is alkaline. pH level below 7.0 is acidic.

Photosensor - Device used to detect light.

Pixel - "Picture element" smallest area or element of an image map.

Platform - Vehicle that carries a remote sensing device.

Point Sampling - Method of grid sampling where a sample is taken in a 10 to 30 ft radius at the center point of each grid location.

Polygon - Area enclosed by a line describing spatial elements.

Positioning System - General system for identifying and recording the location of an object or person.

Post-Processing - Differential correction of GPS position data after it has been collected in the field and stored on a computer or PCMCIA card.

Potentiometer - Device that produces a changing electrical resistance as the relative positions of its components are changed.

Precise (P) Code - Pseudorandom noise code transmitted by GPS satellites.

Precise Positioning System (PPS) - GPS service available to U. S. military that provides users full accuracy with a single mobile receiver.

Precision Farming - Managing each crop production input on a site-specific basis to reduce waste, increase profits, and maintain the quality of the environment.

Pressure Sensor - Device that produces an electrical signal proportional to a fluid pressure.

PseudoRandom Noise (PRN) - Binary sequences of code that have noise-like properties. PRN codes allow all GPS satellites to use a single frequency for transmission.

Pseudorange - Estimation of the true distance from a GPS receiver to a satellite.

Radio Detection and Ranging (RADAR) - Method to determine position or velocity of an object by bouncing high frequency signals off the object and measuring the reflected signal.

Radio Data System (RDS) - Worldwide standard for transmitting digital data along with typical voice or music on a radio frequency.

Radio Technical Commission for Maritime Services (RTCM) - Subcommittee 104 of the RTCM developed standard message formats for GPS signals.

Radiometric System - Yield monitoring system that consists of a radioactive source and a sensor. The mass flow rate of a crop through a harvester is determined by the degree to which the crop obstructs the flow of radioactive particles from the source to the sensor.

Radiometric Correction - Correction to reduce remotely sensed image distortion from variations in radiation levels at the time of sensing.

Raster Format - Format for storing GPS spatial data. The data is stored in cells that are addressed by the row and column of the cell.

Relational Database Management System (RDMS) - Organizes data into a series of records that are stored in linked tables.

Real-Time Correction - Correction of a GPS signal by immediately sending the differential correction information to the mobile receiver on-the-go.

Real-Time Kinematic (RTK) - Procedure in which carrier-phase corrections are transmitted in real time from a reference receiver to the user's receiver.

Rectification - Process of correcting remote sensing image data to eliminate the effects of sensor orientation and distortion present at the time of measurement.

Rectified - Remotely sensed images that have been geometrically corrected to eliminate the effects of sensor orientation and distortion present at the time of measurement.

Registration - Process where one can geometrically align maps or images to allow one to have corresponding cells or feature.

Relief Displacement - Differences in elevation that cause objects to appear to be positioned differently when viewed from an angle.

Remote Sensing - Act of detection and/or identification of an object or series of objects without having the sensor in direct contact with the object.

Repeat Cycle - Time it takes for a remote sensing satellite to view the entire Earth.

Resolution - Way of detecting variation.

Satellite Constellation - System of satellites owned by the U. S. Department of Defense that determines location to within inches.

Satellite Imaging - Process involving the formation of an image collected by a satellite-based remote sensing device.

Satellite Ranging - Method for determining position by measuring distances from several different satellites.

Scale - Ratio or fraction between distance on a map, chart, or photograph and the corresponding distance on the ground.

Scanners - Sensors used to collect remotely sensed data in parallels paths; or, computer equipment used for converting information from paper into digital format that can be read by a computer.

Selective Availability (SA) - Procedure of intentionally introducing error into GPS signals thereby creating a pseudorange error. SA is used as a national security measure to keep non-military receivers from obtaining high-accuracy position information.

Semi-Variance - Measure of how much neighboring data points differ in value.

Semi-Variogram - Line fit to the data in a plot of semi-variance versus lag.

Sensor-Based Variable-Rate Application System - System that adjusts product application rate on-the-go based on information received from real-time sensors.

Serial Port - Connector on a computer that can be used to communicate to other serial devices such as a modem.

Shadowing - Reduction in the level of light hitting an object.

Site-Specific Crop Management (SSCM) - Use of variability of soil and crop parameters to make decisions on the application of production inputs.

Site-Specific Yield Map - Representation of field crop yields collected on-the-go by a harvester equipped with an instantaneous yield monitor.

Software - Programs, procedures, algorithms (set of rules), and their associated documentation for a computer system.

Soil Color Map - Map that provides information on soil texture and levels of soil organic matter (SOM) that can indicate differences in soil patterns within a specific field.

Soil pH - Numerical measure of the acidity or hydrogen ion activity of soil.

Soil Testing - Analysis of soil samples to determine chemical and physical properties.

Soil Texture - Physical structure or character of the soil determined by the relative proportions of the soil components (sand, silt, and clay).

Soil Type - Term used to refer to the combination of primary physical constituents of a soil in a given geographic location.

Space Segment - Portion of GPS consisting of 24 NAVSTAR satellites orbiting the earth.

Spatial - Variation caused by distance separating adjacent pixels.

Spatial Data - Data pertaining to the location, shape, and relationship among geographical features.

Spatial Resolution - Size of the smallest object that can be distinguished by a remote sensing device.

Spatial Variability - Differences in field conditions from one location to another in the same field.

Spectral - Variation from the range of spectral responses covered by a wavelength band.

Spectral Resolution - Ability of a sensing system to differentiate between electromagnetic radiation of different wavelengths.

Spectral Response - Characteristic patterns of radiation reflected or emitted from an object; or, the ability of a sensing system to respond to radiation measurements within a spectral band.

Speed Sensors - Sensors that measure the rotational speed of a shaft of the reflection of radio or sound waves off the ground to determine machine speed.

Spherical Error Probable (SEP) - Measure of accuracy of a three dimensional position estimate produced by a GPS receiver.

Standard Deviation - Measure of the distribution of measurements around their average.

Standard Positioning System (SPS) - Positioning service using a single receiver that is available to any user on a continuous, world-wide basis.

Start of Pass Delay - Delay that allows initial flow of grain before full flow is achieved to be ignored in yield calculations when starting a pass.

State Plane Coordinates (SPC) - Coordinate system similar to UTM using units of feet and using the NAD27 datum. Each state may differ.

Static Features - Objects that do not change in reflectance.

Static Random Access Memory (SRAM) - Electronic data storage device that can be randomly accessed, as opposed to sequentially accessed. Static refers to its ability to retain data as long as power is supplied to the device.

Strain Gage - Device that has a changing electrical resistance as it is deformed.

Sun-Synchronous Orbits - Orbit where each pass of a satellite over a certain point occurs at the same local time.

Temporal - Variation caused by time over the same location.

Thermal Band - Infrared wavelengths of electromagnetic energy.

Thematic Mapper (TM) - Remote sensor designed to create maps of different surface feature categories or "themes." TM has a spatial resolution of 98 ft and is capable of collecting data on seven different bands.

Turn-Key System - Reference to hardware and/or software systems meaning that they are ready to be used immediately and are designed, provided at a cost, and supported by a commercial group.

Turnaround Time - Elapsed time between a satellite taking an image and receipt of that image by the customer.

Universal Transverse Mercator (UTM) - Metric coordinate system used for mapping at scales of 1:500,000 or larger.

User Segment - Portion of GPS consisting of receivers used by civilians and the military for determining position of a person or object.

Variable-Rate Application (VRA) - Adjustment of the amount of cropping inputs such as seed, fertilizer, and pesticides to match conditions in a field.

Variable Rate Technology (VRT) - Applying varying rates of seed, lime, nitrogen, phosphorus, potassium, etc., within each field.

Vector Format - Format for storing and displaying GIS spatial data where the data is stored as points, lines, or areas that create the terrain or map objects.

Vegetation Indexes - Tool for identifying levels of health of plant biomass. Vegetation indexes can be used to assess or predict plant characteristics.

Vegetative Change Map - Map used to identify locations in the field that have undergone changes in vegetative spectral response between two consecutive remote sensing flights.

Waveband - Remote sensing term used to describe a contiguous range of wavelengths of electromagnetic energy.

Yield Monitoring - Regular intervals where a harvested weight has been obtained along with a GPS reading.

Z-Value - Refers to elevation values. The "z direction" refers to upward direction on a 3-D chart or diagram.