Resources - Glossary

ActiveSync - Microsoft ActiveSync is a synchronization software for Windows Mobile-based Pocket PCs. The software is used for data transfer between desktop PCs and PDAs.

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.

Atomic clock - The world’s most accurate clock. Each GPS satellite has an atomic clock on-board, which is used by GPS receivers to calculate position.

Attribute - A characteristic that describes a Feature. Attributes are pieces of information that describe a point, line, or polygon.

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.

Backup - A computer backup is a duplicate set of data that can be used to retrieve files in the event of data loss. Backups are often stored using CD-R, DVD, or USB external hard drives.

Base station - 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.

Card reader - A device that reads removable memory cards such as Secure Digital, Smart Media, CF, and Memory Sticks. Usually connects to PC using an USB port.

CD-R - A recordable compact disc. Most CD-R discs hold up to 650 MB. Can be used for moving large amount of data or as a data backup.

Coast Guard Beacon - Coast Guard Beacon is a differential correction source for GPS. The Coast Guard built the system for maritime navigation. The signal is ground-based and generally available throughout the United States, but may be limited in some areas. The signal is free, but requires a special GPS antenna.

Com port - Communication port is used to connect electronic devices to a computer. It is a 9-pin connector called DB-9.

Compact flash (CF) card - A CF card is a small removable mass storage device. Used as non-volatile memory in digital cameras and PDA devices.

Constellation - Refers to either the specific set of satellites used in calculating positions or all the satellites visible to a GPS receiver at one time.

Coverage - A vector data format for storing the location, shape, and attributes of geographic features. A coverage usually represents a single theme such as soils, streams, roads, or land use. It is one of the primary vector data storage formats for ArcInfo. A coverage stores geographic features as primary features (such as arcs, nodes, polygons, and label points) and secondary features (such as tics, map extent, links, and annotation). Associated feature attribute tables describe and store attributes of the geographic features.

Data logger - Used to store electronic data sent by a measurement device. A yield monitor is an example of a data logging device.

Datum - A set of parameters and control points used to accurately define the three-dimensional shape of the earth. The datum defines part of a geographic coordinate system that is the basis for a planar coordinate system. For example, the North American Datum for 1983 (NAD83) is the datum for map projections and coordinates within the United States and throughout North America.

Digital Elevation Model - DEM - depicts landscape elevation. The data are developed by the USGS at either 10-meter or 30-meter grid spacing. Often used in a GIS as a data layer.

Differential Global Positioning System (DGPS) - is a technique used to improve GPS accuracy. See differential correction.

Differential correction - A technique used to improve GPS accuracy. Differential correction signals remove or reduce errors associated with atmospheric effects and other positioning errors. The correction signal can be land-based or satellite-based. Common sources of differential correction include WAAS, Omnistar, and Coast Guard Beacon.

DOQ - digital orthophoto quadrangle (DOQ) is an aerial photograph. It has been orthorectified--altered so that it has the geometric properties of a map; DOQ's meet National Map Accuracy Standards. Thus the user can measure distances accurately on a DOQ.

DVD - A digital media source capable of storing large amounts of data. Is a common format for movies, but is also used for computer data storage. Each DVD can hold up to 4.7 GB of data.

e00 - ArcInfo interchange format used to transfer coverages. The data must be converted prior to use in a GIS system.

Expansion pack - Is a sleeve that slides on to IPAQ PDA device. The expansion pack may contain extra battery power, memory slots or other enhancing features.

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.

Geostationary satellite - A satellite positioned approximately 35,700 km above the earth’s equator. At this altitude the satellite orbits as fast as the earth rotates on its axis, so it remains effectively stationary above a point on the earth. Satellite-based differential correction satellites are geostationary.

Geosynchronous satellite - A satellite moving west to east whose orbital period is equal to the earth’s rotational period. If the orbit is circular and lies in the plane of the equator, the satellite will remain over one point. Otherwise it will appear to make a figure eight once a day between the latitudes that correspond to its angle of inclination over the equator. The constellation for GPS is geosynchronous.

GeoTiff - GeoTIFF refers to TIFF files, which have geographic data embedded within the TIFF file. The geographic data can then be used to position the image in the correct location and geometry on the screen in a geographic information system.

GIS (Geographic Information System) - 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.

GPS (Global Positioning System) - Global Positioning System is a constellation of 24 satellites, developed by the U.S. Department of Defense, which are used to calculate your position anywhere on earth.

Grain flow dynamics - Refers to the grain flow through the harvest machine. Grain flow dynamics result in errors relating to grain mixing, delayed measurement and resulting positional errors in yield mapping systems.

JPEG - JPEG is a standardized image compression mechanism used to reduce file size. JPEG stands for Joint Photographic Experts Group. JPEG is designed for compressing either full-color or gray-scale images. Often used for internet delivery of aerial photography.

JPW - JPEG World file (JPW) contains coordinate information used to position an image with respect to a coordinate system. JPEG World File format is supported by most GIS software packages. However, the JPW file does not contain projection information and care should be taken to ensure that the coordinate system is the same as other data layers in a GIS system.

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

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 as series of LED lights.

Line - A shape having length and direction but no area, connecting at least two x, y coordinates. Lines represent geographic features too narrow to be displayed as an area at a given scale, such as contours, street centerlines, or streams, or linear features with no area such as state and county boundary lines.

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

Memory stick - A memory stick is a small removable mass storage device about the size of a stick of gum. Used as non-volatile memory in digital cameras and other electronics made by Sony Corporation.

Map Projection - A mathematical formula that transforms feature locations between the earth's curved surface and a map's flat surface. A projected coordinate system includes the information needed to transform locations expressed as latitude and longitude values to x, y coordinates. Projections cause distortions in one or more of these spatial properties--distance, area, shape, and direction.

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

MHz - In computers, is a measure of processor speed. Higher numbers reflect a faster computer processor.

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

Multimedia card - A multimedia card is a small removable mass storage device. Used as non-volatile memory in digital cameras and PDA devices.

Multipath - Interference caused by reflected GPS signals arriving at the receiver, typically as a result of nearby structures or other reflective surfaces.

NAVSTAR - an acronym for NAVigation Satellite Timing and Ranging. NAVSTAR satellites comprise the GPS constellation.

NeATA - Nebraska Agricultural Technologies Association

NMEA - National Marine Electronics Association (NMEA) develops standards for communication protocols. The NMEA interface standard defines electrical signal requirements, data transmission protocol and time, and specific sentence formats. GPS receivers output data using the NMEA 0183 protocol.

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

Operating system - Every general-purpose computer must have an operating system to run other programs. Operating systems perform basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as disk drives and printers.

PDA - Personal Digital Assistant (PDA) are small portable computers, usually handheld or pocket size, that organize data, such as your schedule, appointment calendar, address book, and to-do list. They are also used for GPS navigation and GIS data collection.

PDOP - An indicator of satellite geometry for a constellation of satellites used to determine position. Positions with a higher PDOP value generally constitute poorer measurement results than with lower PDOP value.

Pixel - A pixel is an individual cell in a matrix that comprises a raster dataset. See Raster.

Point - A single x, y coordinate that represents a geographic feature too small to be displayed at as a line or polygon at a specific scale.

Polygon - A two-dimensional closed figure with at least three sides that represents an area.

Processor - A silicon chip that contains a CPU. In the world of personal computers, the terms microprocessor and CPU are used interchangeably. At the heart of all personal computers is a microprocessor. Microprocessors also control the logic of almost all digital devices, from clock radios to fuel-injection systems for automobiles.

Projection - See map projection.

RAM - Acronym for random access memory, a type of computer memory that can be accessed randomly; that is, any byte of memory can be accessed without touching the preceding bytes. RAM is used as temporary memory used to quickly access commonly used files.

Raster - Represents any data source that uses a grid structure to store geographic information. Common examples include remotely sensed data like satellite imagery, scanned data, and photographs.

Re-project - Is the process of converting a map from one map projection to a different map projection. For example, Lat/Long to UTM coordinates.

ROM - Acronym for read-only memory, computer memory on which data has been prerecorded. Unlike RAM, ROM retains its contents even when the computer is turned off. ROM is referred to as being nonvolatile, whereas RAM is volatile.

Rover - Any mobile GPS receiver collecting data during a field session.

RTK - Real-Time Kinematic is a high-end GPS capable of centimeter level positional accuracy.

Scale - The ratio or relationship between a distance or area on a map and the corresponding distance or area on the ground.

Secure digital (SD) card - a small removable mass storage device. Used as non-volatile memory for digital cameras and PDA devices.

Selective availability (SA) - A method of intentional accuracy degradation by the Department of Defense (DoD). With SA turned on GPS accuracy reduced to 100 meters. Selective availability has been turned off as of May 2, 2000. The DoD has no plans to turn SA on in the future. Instead other methods of GPS access will be employed.

Shapefile - A vector data format for storing the location, shape, and attributes of geographic features. A shapefile is stored in a set of related files and contains one feature class, point, line or polygon.

Smart media - Is a small removable mass storage device. Used as non-volatile memory for digital cameras.

Spatial data - Information about the locations and shapes of geographic features; Any data that can be mapped.

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

Synchronize - Synchronizing two devices refers to an exact duplicate between the PDA and PC. If one unit has files newer than the other unit, software will update each unit.

Tabular data - Descriptive information that is stored in rows and columns and can be linked to map features.

TFW - TIFF World file (TFW) contains coordinate information used to position an image with respect to a coordinate system. TIFF World File format is supported by most GIS software packages. However, the TFW file does not contain projection information and care should be taken to ensure that the coordinate system is the same as other data layers in a GIS system.

TIFF - an acronym for Tag(ged) Image File Format. It is one of the most popular and flexible of the current public domain raster file formats. Commonly used in aerial photography and satellite imagery.

Tiger - Topologically Integrated Geographic Encoding and Referencing system - the name for the digital database developed at the U.S. Census Bureau to support its mapping needs for the Decennial Census and other Bureau programs. Data sets include political boundaries, demographics, roads, stream networks.

Unprojected map - A map that is not projected to a coordinate system. Refers to data containing latitude and longitude coordinates.

USB - Communication protocol known as Universal Serial Bus. Commonly used for computer peripherals such as printers, keyboards, scanners, and digital cameras. USB devices allow for hot-swappable capability without restarting the computer to recognize a connected device.

UTM - Universal Transverse Mercator - UTM is a projected coordinate system that divides the world into 60 north and south zones, six degrees wide.

Vector - A coordinate-based data structure commonly used to represent linear geographic features. Features are stored as points, lines, and polygons.

WAAS - Wide Area Augmentation System (WAAS) is a differential correction source for GPS. The FAA built the system for aviation navigation. The signal is satellite-based and only available in the United States. The signal is free and can be used with any WAAS-enabled GPS receivers. No special GPS antenna required.

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.

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.