Arc- A connection between nodes in the vector GIS model.
Accuracy Assessment- Comparison of a classification with ground-truth data to evaluate how well the classification represents he real world.
Ancillary Data- Data from other sources than remote sensing that can be used to aid in the classification.
antenna pattern - diagram of relative signal strength vs direction from antenna
antenna, yagi- type of antenna with strainght elements
Aspect- The compass direction that a surface faces.
Attribute- Characteristic of the feature that is being mapped.
AVHRR- Advanced Very High-Resolution Radiometer.
A meteorological satellite with two bands that is used for large area Earth
observation at 1 km spatial resolution.
AVIRIS- Airborne Visible/Infrared Imaging Spectrometer. An airborne hyperspectral sensor with 224 10 nm bands.
backlobe - lobe to the back of an antenna
Band- Data values for a portion of the electromagnetic spectrum, sometimes called a channel.
BNC - common rf connector with bayonet style attachment
Boolean Arithmetic- Analytical expression that uses a true or false condition. It usually contains logical expressions (e.g., Distance from edge > 50 m) and Boolean operators (not, and, or).
Boolean Operator - Boolean operators are used to combine logical expressions into a complex expression.
bpm - beats per minute
Buffer- A zone of specified distance from selected features.
Cell- A single unit in the raster GIS data model. A location, containing area, defined by a line and column coordinate.
Class- A set of pixels in a GIS or image file that represent areas that have the same attribute or share the same condition. Classification The process and operations used to assign pixels of a continuous raster image to predefined classes.
Classification Scheme- Hierarchical system of user-defined classes for the classification of remote sensing imagery.
Clusters- Natural groupings of objects created by cluster analysis. In a cluster, objects are mutually closer to each other than to objects in other clusters.
Cluster Analysis- Techniques that group objects (e.g., pixels) into clusters according to user-defined rules.
Continuous Data- Quantitative data that varies continuously throughout a raster layer.
coax - cylindrical cable used for radio signals, often used to connect antenna to receiver
Contour Map- An elevation map in which lines connect points of equal elevation.
Coordinate System - Method of describing locations by columns and rows, or x and y values.
Coverage- Geographic data set that represents a specific type of feature (e.g., vegetation coverage). Often simply called a layer. ARC/INFO also has a data format that is referred to as a coverage.
Database- Relational data structure used to store, query, and retrieve information.
dB- decibel, logarithmic representation of a ratio often used to express gain or loss.
dBd - decibels with respect to a dipole (basic antenna element)
dBi - decibels with respect to an isotropic radiator (antennas)
dBm - decibels with respect to one milliwatt
dBW - decibels with respect to one Watt
DEM- Digital Elevation Model. A GIS raster layer representing elevation. This is a common GIS product created at a variety of scales.
Digitizing- Process and operations for encoding graphic data into some numeric system (e.g., X, Y - coordinates) and storing it on a computer.
dipole - a basic antenna element to which most other antennas are compared for gain
DLG- Digital Line Graphs. Standard line vector product of the USGS. Includes such themes as roads, rivers, railroads, etc.
Electromagnetic Spectrum- Range of electromagnetic waves or radiation that is the result of energy emitted by hot objects (e.g., the sun).
elements - components of an antenna that are aligned to increase gain
Enhancement- Techniques used to make a remote sensing image more interpretable.
Euclidean Distance- Distance between objects or values that is computed as a straight line.
Front-to-back ratio - specification for antennas, forward gain relative to reverse gain gain - factor of amplitude
Geocoded Data- Image that has been rectified to a map projection and cell sizes, and has been radiometrically corrected.
Georeferencing- Assigning map coordinates to an image. Usually involves resampling of pixels to extrapolate the values for the new pixels.
GIS- Geographic Information Systems. "Decision support system involving the integration of spatially referenced data in a problem solving environment (Cowen 1988)".
GPS- Global Positioning System. A receiver that calculates its absolute geographic position by determining its relative position to a set of at least three satellites.
Ground-truth Data- Data about a feature collected in the field.
Ground-Truthing- Acquiring data about features of interest in remote sensing by collecting ground-truth data in the field, inspecting aerial photography, additional maps, other ancillary data.
Hyperspectral- The use of many narrow sections of the electromagnetic spectrum in remote sensing.
Hz - cycles per second, unit for frequency
Image- Picture or graphical representation. In remote sensing and GIS as a term that describes digital representations of earth features.
Image Processing- Manipulation of an image to improve or change some quality of the image.
Interval Data- Data that is divided into ranges and in which the distance between the intervals is meaningful.
ISODATA- Clustering Iterative Self-Organizing Data Analysis Technique. A clustering method used in image classification.
Kappa Coefficient- Compares the results of an image classification to the results of a random classification.
kHz - a thousand cycles per second
Land Cover Map- Map of ground features that can be differentiated on a scene (e.g., urban areas, bare land, pasture, etc.).
Landsat TM- Landsat Thematic Mapper. Earth observation satellite with seven bands at 30m spatial resolution.
Landsat MSS- Landsat Multispectral Scanner. Earth observation satellite with 4 bands at 80m spatial resolution.
Layer- Distinct map theme. Usually a separate GIS file.
Line- A 1-dimensional connection between two points (has length).
lobes - local maxima in antenna pattern
MHz - a million cycles per second
MMU- Minimum Mapping Unit. The smallest area (usually a polygon) mapped.
Multispectral Classification- Process of sorting pixels into distinct classes based on their spectral characteristics in multiple band of electromagnetic wavelengths. Usually involves decision rules and cluster analysis.
MSS- see Landsat MSS above
mV - millivolts
mW - milliwatt
NAPP- National Aerial Photography Program. Standard USGS aerial photography product. It is typically a 9"X9", 1:40,000 scale, color-IR image.
NF - noise figure
Node- Topological connection point between two or more arcs, within the GIS vector model.
NWI- National Wetlands Inventory. A project of the USFWS to map all of the wetlands in the U.S. at a scale of 1:12,000. A common and available GIS vector layer.
Ordinal Data- Data are group in classes and the order between the classes is important (e.g., order in a stream network).
Overlay- A combination of two or more map layers, within a GIS, to create one or more new map layers or new information.
Panchromatic- Imagery Single-band or monochrome imagery.
Pixel- A "picture element". See Cell above.
Point- A pair of coordinates representing a location with 0 dimensions.
Polygon- 2 dimensional vector object (i.e., has area). Polygons are defined by a set of arcs with a common topology.
Projection- A model of the Earths surface for mapping (usually in 2 dimensions).
Quad- Short for quadrangle. A standard map size and scale used by the U.S. Geological Survey.
Radiometric Correction- Correction of variation in data values that is caused by sensor malfunctions and atmospheric conditions.
Radiometric Enhancement- Techniques that correct and improve radiometric values of individual pixels.
Raster- Common GIS data model made up of a grid of cells or pixels. Each pixel contains a single value.
Rectification- Making an image conform to a map projection system.
Registration- Making two images conform to one another.
Remote Sensing- "Remote sensing is the science of deriving information about the earth's land and water areas from images acquired at a distance. It usually relies upon measurement of electromagnetic energy reflected or emitted from the features of interest (Campbell 1987)."
Resampling- Extrapolating pixels values for a new grid from values in an old grid. It is applied after an image is rectified to a projection system or registered to another image.
Resolution- The degree of discrimination between objects. It can be spatial (what is the smallest size and object needs to be to be observed). It can be spectral (number and size of area of the electromagnetic spectrum is required). It can be temporal (how often does the subject need to be observed).
Scale (maps)- A comparison of measurement on a map to measurement on the Earth, usually represented by a fraction or ratio. Also, a measure of detail in a map. Scale can be a difficult concept. Ecologists refer to efforts over a wide area as large scale, while geographers label efforts with greater detail over a smaller area as large scale. Geographers call this application large scale because the scale fraction (e.g., 1/24,000) is a larger number than broad area scales (i.e., 1:250,000 is a relatively small number compared to 1/24,000). This translates into confusion, especially in GIS where these two fields are merged. To circumvent this problem we use the terms fine scale for small area projects with higher detail and broad scale for large area projects with less detail.
sidelobes - lobes to the side of an antenna
Signature- Set of statistics that describe and define a training sample or cluster. It is used in multispectral classification. See also spectral response pattern and spectral signature.
Slope- Percentage or degree change in elevation over a defined distance.
SNR - signal to noise ratio
Spatial Enhancement- Enhancing values of pixels in an image relative to surrounding pixels.
Spectral Distance- A decision rule for image classification that assigns pixels to a cluster based on the minimum difference in spectral values to other pixels.
Spectral Enhancement- Modifying pixel values in an image to enhance certain feature over others.
Spectral Response Pattern- Degree to which an object reflects incident electromagnetic energy in different regions of the electromagnetic spectrum.
Spectral Signature- see Spectral Response Pattern.
SPOT- Le Systeme Pour 'l Observation de la Terre (French Earth observation system). This satellite captures either 10 m panchromatic or 20m 3 band multispectral imagery.
Supervised Training- Image classification procedure in which the analyst selects groups of pixels, determines their spectral response pattern (signature), and trains a computer system to recognize pixels based on this spectral response pattern
Suitability Map- Suitability means relevancy according to a set of predefined criteria. A suitability map displays locations that fulfill all criteria.
Thematic Data- Qualitative and categorical raster data, usually map or land cover classes such as pasture, urban areas, standing water, etc.
TM- see Landsat TM above
Topology- Method of determining spatial relationships in vector data models (tells computer what is inside or outside a polygon or which nodes are connected by arcs). Turns vector nodes, arcs, and polygons into intelligent maps.
Unsupervised- Training Image classification procedure in which the computer identifies inherent patterns in the spectral data and uses a clustering algorithm to order pixels into discrete classes.
USGS- United States Geological Survey. The USGS is an organization geared toward providing reliable scientific information to describe and understand the Earth; minimize loss of life and property from natural disasters; manage water, biological, energy, and mineral resources; and enhance and protect our quality of life. USGS is made up of 4 divisions: the National Mapping Division, the Biological Resource Division, the Water Resources Division, and the Geologic Division.
Vector- Common GIS data model made up of points, lines, or polygons, with associated attributes.
Additional terms and definitions can be obtained from the EROS Data Center at http://edcwww.cr.usgs.gov/glis/hyper/glossary/index.