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The storage of electromagnetic energy and the release of it at a later time in a different wavelength; one of the three main processes that electromagnetic energy undergoes in the earth's atmosphere (see also reflection and scattering).
Absorption band
The wavelength interval(s) at which electromagnetic energy is absorbed rather than reflected or scattered.
In general, accuracy is how consistent the observation is with reality; in other words, how correct is the data compared to the real world.  Often in remote sensing, it is communicated as a matrix of omission and commission errors.
Across track scanner
A scanner with sensors that sweep across its path as it moves across the earth's surface, as compared to a pushbroom scanner.
Address match
Tying a location or event to an address or determining what political boundaries an address lies.
Address range
Those addresses within a specific location or numerical range.
Adjacency List
An alternative to an adjacency matrix, includes node adjacency and connectivity data, a node with an entry of zero, there are no arcs emanating from that node
Adjacency Matrix
An alternative representation of connectivity and adjacency data for nodes.
Advanced Very High Resolution Radiometer (AVHRR)
A sensor based on National Oceanic and Atmospheric Administration satellites that collects data in the visible, near infrared and thermal infrared portions of the electromagnetic spectrum and has a pixel size of 1.1 km.
Aerial photography
The collection of remotely sensed data from a platform flying above the earth's surface, but not in orbit, such as an airplane (both manned and unmanned) or a kite.  Aerial photography is often used for mapping.
Airborne Imaging Spectrometer (AIS)
Airborne Laser Terrain Mapping (ALTM)
Airborne Visible Infrared Imaging Spectrometer (AVIRIS)
Imaging from high-altitude (U2, about 15 km altitude, 20m resolution) and low-altitude (Twin Otter, 3 km altitude, 4m resolution) aircraft.
The ratio of the amount of energy reflected by an object to the amount incident upon it, often expressed as a percentage.
The distribution of a resource.  The term is often used in the context of a Location-Allocation Model.
Along track scanner
Ancillary data
Additional material or information that assists in the interpretation of aerial photography or remotely sensed imagery.
Atmospheric correction
Atmospheric effects
Atmospheric transmission
Atmospheric window
The process by which the strength or energy of something decreases as it gets farther from the energy source.
The angular orientation of the platform upon which the remote sensor is based.
The direction of a line measured clockwise from a reference direction, given as an angle.
What the object of interest being sensed must be more visible than in order to be detected.
Background noise
The ever present system noise, not dependent upon whether or not there is an object being sensed.
A selection of wavelengths (i.e., band 7 of ETM+).
Band pass filter
A wave filter with a single transmission band with a low cut off point and a high cut off point.
Bidirectional reflectance
Comparing an instrument's results against a standard.
In photogrammetry, a line drawn from the center point of a vertical photograph through the transposed center from an overlapping photograph.  In transportation, the centerline of a road, which is of rather high interest.
Change detection images
Dependent upon the wavelengths an object reflects.
Color composite
An image created by assigning a specific color to a spectral band in a multispectral image.  Colors limited to three (i.e., blue, green, red), therefore only 3 bands can be shown at one particular time.  Different features can be highlighted using different band combinations.
Color infrared
Composite photograph
In aerial photography, created by combining photos taken from different lenses of a multi-lens sensor.
In aerial photography, the difference between light and dark, i.e., highlights and shadows.
Contrast enhancement
Contrast stretching
Control point
The ground area represented in a map or image.
Data accuracy
Data processing
The application of procedures, i.e., algorithms, filters, etc., that change the data from their original form.
Data quality
Density slicing
Dielectric constant
Difference image
Digital elevation model (DEM)
A grid of elevation values.
Digital number
Directional filter
Discriminant function
The separation of electromagnetic radiation into its separate components.
In aerial photography, a shift in the position of the image which alters the perspective characteristics.
Distribution function
Doppler effect
A change in the observed frequency of electromagnetic radiation because of the relative motion between the source and the sensor.
Doppler principle
Doppler radar
Radar sensor that detects and interprets the Doppler effect in terms of the radial velocity of a target.
Doppler shift
Dynamic segmentation
Manages the QuickBird satellite, as well as provides a variety of other products and services.
Edge enhancement
Electromagnetic radiation (EMR)
Electromagnetic spectrum (EMS)
Ranges from cosmic rays through gamma rays, X-rays, ultraviolet radiation, visible radiation (blue, green, red), infrared radiation and microwave radiation.  Each part of the EMS provides different information to trained analysts.  Each surface has different properties as to whether they reflect or scatter or absorb the energy.
Height above a datum.
The process by which an object or body emits electromagnetic radiation, often as heat (temperature).
Symbol ?, a special case of exitance for a material with a specular surface and is opaque.
Also known as exitance (symbol M), the ratio of the emitted flux per unit area emitted to that of a black body at the same temperature and under the same conditions.  M=Wm-2.
Energy flux
Enhanced Thematic Mapper Plus (ETM+)
Instrument onboard the Landsat 7 satellite.  This is the most recent of the sensors to fly onboard the Landsat series of satellites.  ETM+ has seven spectral bands, including visible, near infrared, shortwave, and thermal infrared.  The panchromatic band (visible to near infrared) has a pixel size of 15 m, the thermal infrared band has a pixel size of 60 m, while all the others have a pixel size of 30 m.  Typical applications include land use/land cover analyses, environmental monitoring, climatology, oceanography, ice and snow cover analyses, coastal studies, and soil applications.
EROS Data Center
The U.S. Geological Survey's Earth Resources Observation System Data Center located in Sioux Falls, South Dakota.  Houses the USGS collection of imagery and satellite data, including Landsat 7 ETM+ data.
Symbol M, the radiant flux per unit area emitted by a surface.
False color composite
False color image
Field of view
The solid angle through which an instrument is sensitive to radiation.  In other words, it is the area we can see through the camera lens.
In aerial photography, a material placed between the sensor and the object to modify the information recorded.  In remote sensing, a filter is often an algorithm run on the data to change the data in some manner.
Flight path
The path made by the vehicle carrying the sensing instrument.
Forward and Reverse Star Representation
Forward overlap
Fourier analysis
The number of oscillations per unit time, or the number of wavelengths that pass a point per unit time.
Statistics, a normal distribution
Conversion of analog into digital
Geographic Information Science (GIS)
The science of manipulating spatial data, includes archiving, retrieval, display, and analysis of these data.
Geographic Information System (GIS)
Software used to manipulate spatial data.
Geographic Information System - Transportation (GIS-T)
Geographic Information Systems and Science with a focus on transportation related problems, research, and applications.
Geographic Positioning System (GPS)
Geometric correction
Grid format
Ground control point (GCP)
Ground range
The distance from nadir to an object.
Ground range image
Ground receiving station
Ground truth
Term referring to data and information collected by a person on the earth's surface for use in validating data and information gathered from aerial photography or satellite imagery.
A unit of frequency, Hz=cycles per second
High pass filter
A statistical graph showing the frequency of values of a satellite image.
Red, blue, yellow, or green.
Data, such as AVIRIS, collected in hundreds of small yet distinct spectral bands.
The IKONOS instrument collects data in the visible to near infrared portions of the electromagnetic spectrum. The panchromatic band has a resolution of 1 m while the other bands have a resolution of 3 m. Applications of IKONOS data include mapping, precision agriculture, forestry, oil and gas exploration, insurance, utilities, real estate, military, transportation, and international diplomacy.
Light striking the surface of an object.
The recorded data collected by an instrument.
Image enhancement
Image processing
Image striping
Imaging spectroscopy
Incidence angle
Index of refraction
Symbol n, measurement of amount of refraction.
Indian Remote Sensing (IRS) Satellite
Onboard the IRS satellite, there is a Linear Imaging Self Scanner (LISS) instrument which collects data in the blue, green, red, and near infrared parts of the electromagnetic spectrum.  On the most recent instrument, the blue band was replaced with a shortwave infrared band.  Also, during the instrument's history, the pixel size has steadily shrunk, going from 72.5 m to 23 m.  Typical applications of IRS data include agriculture, water resources, forestry, ecology, geology, water shed management and analysis, marine fisheries, and coastal management.  IRS data are also available through Space Imaging.
Inductive loop detector
Infrared (IR)
Portion of the electromagnetic spectrum that is just beyond the visible red.  It is often radiation emitted by a hot body.
Instantaneous Field of View (IFOV)
Intelligent Transportation Systems (ITS)
Intensity, hue, saturation (IHS)
Interactive processing
Interferometric synthetic aperture radar (IFSAR)
Interpretation key
Subsets of photographs and satellite imagery that have been clearly identified, often used for vegetation, soil, rocks, with a variety of samples of each, from different season, different lighting conditions, etc.  Used by photo interpreters to assist in the interpretation process.
The measurement of radiant flux incident on a surface, in watts (energy per unit time).
On a map, a line drawn connecting points with similar values, such as elevation or temperature.
Isotropic radiation
Diffuse radiation with exactly the same properties in all directions.
Ka band
A thermometer scale.
L band
Lambertian surface
A series of satellites launched by the U.S. since 1972, with MSS, TM, and ETM+ instruments onboard.
Laplacian filter
Large scale
The cartographic definition of large scale is a small area mapped in great detail.  It is also often used to refer to large areas of the earth's surface that have not been mapped in great detail, but a large area is shown.
Light Amplification by Stimulated Emission of Radiation.
Displacement of the top of an elevated feature.
Light Detection and Ranging (LIDAR)
Light Detection and Ranging, the laser equivalent of radar.  A laser swath is emitted and the return beam is sensed, usually by a low-altitude aircraft.  This enables accurate distance ranging, and the consequent ability to produce ~20cm contour maps and 3-D oblique images.  The technique is sometimes called Airborne Laser Terrain Mapping or ALTM.
Linear referencing
Line drop out
Line pair
Location allocation
Look angle
Look direction
Look up table (LUT)
A depiction of the earth's surface.
Map matching
Map projection
The mathematical transformation required when displaying the round earth on a flat surface.
Median filter
Medium scale
Data about data -- the data describing the data set, imagery or map.
Mid-infrared (MIR)
Mie scattering
Minimum ground separation
Mixed pixel
Modulation Transfer Function (MTF)
Multiple Endmember Spectral Mixture Analysis (MESMA)
Sensing in usually 4 distinct wavelength bands (equivalent to colors, not all of which are visible to the human eye).  Because the data handling capacity of the sensor is spread over these different wavelengths, this usually translates to lower resolution than panchromatic.  Also see hyperspectral.
Multispectral classification
Multispectral scanner
Multivariate analysis
National Aeronautics and Space Administration (NASA)
NASA Headquarters

Goddard Space Flight Center, Greenbelt, MD
Jet Propulsion Laboratory, Pasadena, CA
Johnson Space Center, Houston, TX
Kennedy Space Center, FL
Marshall Space Center, Huntsville, AL
Ames Research Center/Moffett Field, Mountain View, CA
Stennis Space Center, MS
National High Altitude Photography (NHAP)
National Imagery and Mapping Agency (NIMA)
National Oceanic and Atmospheric Administration (NOAA)
Near infrared (NIR)
Network arc
Network link
Node-Arc Incidence Matrix
Node-Node Adjacency Matrix
Nondirectional filter
Non-selective scattering
Origin-destination flow matrix (O-D matrix)
Placing of layers containing different information over each other.  These layers are registered to a common map.
Sensing in a single wide band, resulting in high-resolution monochromatic image.  Contrast against multispectral and hyperspectral .
Parallel polarized
Passive microwave
Passive remote sensing
Picture element (pixel)
The smallest resolution unit.
Planck's law
This equation is used to calculate the spectral emitted radiance from a blackbody at a given temperature. Ll =((2hc2)/((l 5)(ehc/k lT -1))) , where h=6.625x10-34Js (Planck's constant), c=3x108 ms-1 (speed of light), and k=1.38x10-23JK-1 (Boltzmann's constant -- not the same as Stefan-Boltzmann)
Where a sensor is based, i.e., a satellite, aircraft, or other flying object.
Polar orbit
Polarized radiation
Principle component analysis (PCA)
Prinicipal point
Probability density function (PDF)
Pushbroom scanner
Q-tree (Quad Tree)
A method for compressing raster data.
Sensor flown onboard a satellite with the same name.  The panchromatic band has a resolution of 1 m while the blue, green, red, and near infrared bands have a resolution of 4 m.  Typical applications include agriculture, mapping, environmental monitoring, emergency monitoring, and forestry.
Radar altimeter
Radar scatterometer
Radar shadow
Radiant energy peak
Radiant flux
Radiant temperature
A grid of data points, as opposed to vector.
Ratio image
Rayleigh criterion
Rayleigh scattering
Real aperture radar
Real time
Relief displacement
Remote sensing
The act of recording data of the earth's surface from an instrument located away from the object being recorded.  Often refers to the whole field of aerial photography, interpretation, satellite data, and processing and analysis of the data.
Representative fraction (RF)
Also known as scale, the relationship of a unit on the map, image, or photo with units on the ground.
Reseau marks
Often the carrier of an instrument that collects data of the earth's surface.
Also known as the representative fraction, it is the relationship of a unit on the map, image or photo with units on the ground.
Scan line
A single remote sensing image.
The instrument, often based on a satellite or aircraft, that collects data of the earth's surface.
Shortest path
An algorithm in GIS that calculates the shortest route from one location to another.
Shortwave infrared (SWIR)
Shuttle Imaging Radar (SIR)
Shuttle Multispectral Infrared Radiometer (SMIRR)
Shuttle Radar Topographic Mapping mission (SRTM)
Side-looking airborne radar (SLAR)
Side-scanning system
Signal to noise ratio
Slant range
Small scale
Can either mean data or a map that covers a large area of the ground with minimal detail (cartographic definition) or a small area of the ground in great detail.
Sound Navigation Ranging (SONAR)
Space Imaging
The company that launched and now distributes imagery collected by the IKONOS instrument.
Spatial frequency filtering
Spatial resolution
The size of the pixel in the image.
Spectral band
Spectral interval
Spectral reflectance
Spectral resolution
Spectral sensitivity
Spectral signature
See electromagnetic spectrum.
Specular reflectance
There are two instruments onboard the SPOT satellite:  HRVIR and VEGETATION.  HRVIR has a panchromatic band (10 m resolution) and 5 spectral bands (20 m resolution) that collect data in the blue, green, red, near infrared, and mid infrared portions of the electromagnetic spectrum.  The VEGETATION instrument has 4 spectral bands (blue, red, near infrared, and mid infrared) with a pixel size of 1.5 km.  General applications of SPOT data include environmental monitoring and land use/land cover studies.
SPOT Image
French company that launches the SPOT series of satellites and serves as the SPOT data provider.  Also provides a variety of other data products.
Stefan-Boltzmann constant
s=5.67x10-8Wm -2K-4
Stefan-Boltzmann law
E(T)=s T4, where s =5.67x10-8Wm-2K-4 (Stefan-Boltzman constant), T=temperature in degrees Kelvin; essentially states that the radiant flux of a blackbody is equal to temperature to the 4th power times the Stefan-Boltzmann constant.
Stereo model
Stereo pairs
Two overlapping aerial photographs which can be viewed in stereo.
A subset of a remotely sensed image.
Supervised classification
Categorization of a remotely sensed image using input from the human operator as well as additional inputs such as training sites.
Swath width
The width of the area imaged by a satellite sensor as it sweeps over the earth's surface.
Synthetic aperture radar (SAR)
An instrument flown onboard the Canadian Radarsat.  The SAR is an active microwave instrument that sends signals to the Earth's surface and processes those signals as they return to the instrument.  An advantage to using this type of system is the ability to acquire imagery day or night, and through clouds.  Typical applications include ice monitoring, coastal surveillance, coastal and open ocean monitoring, cartography, land use studies, geology, environmental monitoring, hydrology, agriculture, and forestry.  Space Imaging provides Radarsat SAR data.
Systematic distortion
Systeme pour l’Observation de la Terre (SPOT)
Series of satellites launched by SPOT Image, currently SPOT 5 is on target to launch in late 2001.
Temporal resolution
How frequently a site is imaged by a satellite, i.e., daily, weekly.
The frequency and arrangement of tones in an aerial photograph.  The smoothness or roughness of an object can be a clue to its identity.
Thematic Mapper (TM)
An instrument flown on the Landsat series of satellites.  Data can be purchased through the EROS Data Center.
Thermal infrared (TIR)
Also known as far infrared, refers to the 3.0-5.0 mm and 8-14 mm portions of the electromagnetic spectrum.
Tie point
Each distinguishable shade in the gray scale varying from black to white, used most often in aerial photo interpretation.
Refers in general to maps and data that show at the least elevation and land form features.
The relationship (i.e., adjacency and connectivity) of features in a data set
Tracking and Data Relay Satellite (TDRS)
Traffic calming
Training site
A portion of a remotely sensed image chosen by the interpreter to use in a supervised classification to "train" the computer in what to look for.
An intrinsic property of a material; the ratio of energy transmitted by a material to total incident radiation.
A measured quantity; the ratio of energy transmitted by a material to total incident radiation.
Turn table
Ultraviolet (UV)
The 0.01-0.4 mportion of the electromagnetic spectrum.
Uncontrolled mosaic
United States Department of the Interior (US DOI)
Information from USDOI website:  "The Department's mission is (1) to encourage and provide for the appropriate management, preservation, and operation of the Nation's public lands and natural resources for use and enjoyment both now and in the future; (2) to carry out related scientific research and investigations in support of these objectives; (3) to develop and use resources in an environmentally sound manner, and provide an equitable return on these resources to the American taxpayer; and (4) to carry out trust responsibilities of the U.S. Government with respect to American Indians and Alaska Natives.  The Department collects revenues from the leasing of natural gas and oil resources, both offshore and onshore; from coal, timber, and grazing on Federal lands, and from numerous other sources, such as recreation fees.  The Department of the Interior is comprised of a number of bureaus and offices including the Bureau of Indian Affairs, the Bureau of land Management, the Bureau of Reclamation, the Fish and Wildlife Service, the U.S. Geological Survey, the Minerals Management Service, the National Park Service, the Office of Surface Mining, the Office of Insular Affairs, and the Office of the Secretary."
United States Department of Transportation (US DOT)
Mission statement:  "Serve the United States by ensuring a fast, safe, efficient, accessible and convenient transportation system that meets our vital national interests and enhances the quality of life of the American people, today and into the future."
United States Geological Survey (USGS)
The USGS serves the United States by providing reliable scientific information to describe and understand the earth, as well as enhance and protect our quality of life (from USGS mission statement).  The USGS provides access to a variety of cartographic and remote sensing products, including Landsat 7 ETM+ data, aerial photographs, and topographic maps.
Unsupervised classification
Data in a remotely sensed image are placed into categories by the computer with no assistance by the human operator.
In remote sensing, the act of applying statistical methods to determine the accuracy of a map or data set derived from remotely sensed data.
Average squared deviation around the arithmetic mean, a measurement of variability.
An atmospheric sounder carried onboard the NOAA GOES satellites.
Vector format
In GIS, refers to a data structure utilizing nodes and arcs, as opposed to raster.
Vegetation anomaly
Vertical exaggeration
Very near infrared (VNIR)
Visible Infrared Spin-Scan Radiometer (VISSR)
Carried onboard the NOAA GOES satellites.
Visible radiation
The portion of the electromagnetic spectrum that humans can see, from 0.4-0.7 mm (blue, green, and red).
Visual dissonance
Volume scattering
Symbol is W.
Symbol is lthe distance between successive crests, troughs, or other point in a harmonic wave.
Wien's Displacement Law
lmax= peak wavelength of emission = (2897mm K)/T where T is temperature in degrees Kelvin, useful for determining the temperature of an object
The portion of the electromagnetic spectrum that allows optimal transmission and minimal attenuation through a particular medium.
A portion of the electromagnetic spectrum:  radar, 2.4-3.8 cm.
Aircraft rotation around the vertical axis.
Opposite of nadir, the point directly above in the sky.

Last Updated: May 10, 2001