Glossary

Area - The size of a two dimensional feature. The shape can be a fully closed polygon, or set of contiguous raster cells. [1]

Attributes - Non-spatial characteristics of a particular feature or raster cell typically stored in a table. [1]

Azimuth - The angular distance from a fixed point measured clockwise from north where north is typically 0°, east is 90°, south is 180°, and west is 270°. It is also often expressed as the angle of the light source (e.g. the sun).

Binary - Number system used in computers, there are only 2 values, equal to either 0 or 1.

Bitmap Files - A format for image (or picture) files. The quantity of shades of gray or number of colors represented by a bitmap image is determined by the number of bits per pixel. [1]

Buffer - Useful in proximity analysis, a buffer is defined as the zone around a map feature, and may represent units of time or distance. [1]

Cardinal Point - One of the four principle compass directions, i.e. north, south, east, and west.

Cell - Smallest unit on a map or grid (i.e., raster data).

Centroid – The geometric center of a shape, center of gravity or balance for a particular shape, center of area for a 2D shape, center of volume for a 3D shape.

Classification - Method of grouping features with common attributes or qualities and assigning the same symbol to members of the same group.

Color Palette - Allows the user to select the color, outline, and transparency of an object.

Color Ramp - Various shades of a particular color (or range of colors) used to depict values or ranking on a map. Population density and temperature are typically portrayed on a map in this fashion. [1]

Contour - Line on map that connects points of equal value (typically elevation).

Coordinate System - Reference used to define the position of points, lines and/or places in space that forms a grid. Typical examples of coordinate systems include the geographic coordinate system and the Cartesian coordinate system. [1]

Coverages - A type of data model for storing geographic data, typically represent a layer such as streams, or roads. Attributes of features are stored in independent tables. Note, coverages cannot be edited in ArcGIS 8.3 or later versions. [1]

Dangle Tolerance - Minimum length allowed for dangling arcs in ArcInfo coverages, removed by the CLEAN process. [1]

Dangling Arc - Occurs when a polygon is not closed correctly, the arcs either do not connect (undershoot) or a small fragment of an arc extends beyond the intersection (overshoot). Dangling arcs may not necessarily be an error (e.g., they may represent dead-end streets, or cul-de-sacs in a road network). [1]

Data Frame - Defines numerous display properties for layers in ArcMap (e.g., page extent, coordinate system, geographic extent) and can be used to organize layers that share the same coordinate system. [1]

Data View - Used to examine, view, and query the spatial data of a layer, when in this view no map elements (e.g., title, north arrow, scale bar) are visible.

Datum - Reference specification from which maps are drawn; set of control points used to determine the shape of the Earth, coordinate positions on the surface (horizontal datum), and/or the height above or below a surface (vertical datum). [1]

Decimal Degrees - Measure of longitude and latitude values expressed in decimal format. Longitude values for the western hemisphere are negative values, latitude values for the southern hemisphere are negative.

Digitizing - Process that converts an image or map into a digital image able to be recognized and used by the computer.

Dissolve - Used to simplify a line or polygon by removing boundaries between adjacent features with the same attributes or values. The result is the replacement of multiple features with a single feature.

Easting - Distance east of the origin in the UTM coordinate system.

Export - Process used to move data from one program or system to another, and typically from one file format to another. [1]

Feature Classes - Defines a group of geographic items having the same basic characteristics such as geometry (point, line, or polygon), attributes, and spatial reference. Feature classes allow for efficient data storage by grouping similar features together (e.g., different types of roads may be grouped together into a single feature class named “roads”). [1]

Feature Dataset - Contains feature classes that share a common coordinate system and whose features reside within the same geographic area. [1]

Features - Object on a map that represents a real world object such as a road or river.

Field - Place in database (i.e., column in a table) where information about a single attribute is stored. [1]

File Extension - Typically three or four letters preceded by a period at the end of a file name that identifies the file"s format or application used to make the file.

File Name - Unique name used to identify a particular document.

Fuzzy Tolerance - Used to correct faulty intersections between polygons or lines, when two points are separated by a very small distance they will be joined or "snapped" together. This distance is call the fuzzy tolerance.

Geodatabase - Short for Geographic database. Used to store, manipulate, and query geographic information about locations such as single points or other objects.

Geographic Coordinate System - Defines the locations of points based on longitude and latitude on the Earth.

Geographic Information Systems (GIS) - Computer-based methods of recording, analyzing, and displaying geographic information, able to link data typically found on maps (roads, rivers, boundaries) with observations typically not conveyed through maps such as population density, vegetation type, etc.

Global Positioning System (GPS) - System of satellites used to compute the positions of objects on the Earth.

Globe View - Allows the globe to be viewed in ArcGlobe.

Hemisphere - Half of a sphere, most commonly used to describe half of the Earth as in the northern hemisphere (north of the equator), southern hemisphere (south of the equator), eastern hemisphere (east of the prime meridian), or the western hemisphere (west of the prime meridian).

Hillshading - Method used in topographic maps to convey terrain instead of contour lines by modeling the hypothetical illumination of the surface by the sun.

Histogram - Graph that groups the data according to the number of times (or frequency) of occurrence. The values are organized along the horizontal axis and the frequency of occurrence is measured along the vertical axis.

Import - Process that enables you to bring data in from other sources or programs and integrate it with existing data.

Infrared Radiation (IR) - Electromagnetic radiation with wavelengths longer than those the visible radiation. Remote sensing techniques can use infrared radiation to measure physical chemical properties of surfaces (e.g., vegetation cover, chemical composition of surfaces). [2]

Intersect - Combination of multiple data sets that preserves features within a common area.

Joining - Method of appending the values of one table to another based on a common field or attribute. [1]

Labeling - Text placed near a feature that describes and/or identifies it.

Latitude - Angular distance north or south of the equator (typically in degrees).

Layout View - Similar to a print preview, shows the map and map elements (scale, north arrow, etc.) as they would look on a printed page.

Legend - Defines the symbols on a map (also referred to as a Key).

Line - Lines are formed by the connection of points and may be straight or curved.

Longitude - Angular distance east or west of the Greenwich prime meridian (in England). All longitudinal lines pass through the North and South Poles.

Mask - Allows particular data to be omitted from analysis or covered from view.

Natural Breaks Classification - Method that uses a statistical formula called the Jenks optimization to divide data into groups/classes based on the original data distribution. [1]

North Arrow - Symbol on a map that tells which direction is north.

Northing - Distance north of the origin in the UTM coordinate system.

ObjectID - Unique identification for a feature or record in ArcGIS. [1]

Overlay - Combination of 2 or more layers sharing a common coordinate system.

Pan - To move an image or a map in the display window without changing the scale. [1]

Personal Geodatabase - Storage of geographic data in Microsoft Access. Only one person at a time can edit the data, though multiple people may read the data at the same time. [1]

Pixel - Smallest unit of information in an image. Higher resolution images will have a larger number of pixels than lower resolution images.

Point - Location defined by a pair of x, y coordinates.

Polygon - Closed, multi-sided shape defined by connecting a sequence of multiple points, in which the first and last point is the same.

Prime Meridian - Imaginary line that runs north to south through Greenwich, England dividing the earth into eastern and western hemispheres; it also serves as the origin (0°) for the measurement of longitude.

Projection - Method that allows the curved surface of the Earth to be illustrated on a two-dimensional (flat) map.

Pyramid - Used in raster data sets. A method of enhancing display performance by copying original data in decreasing levels of resolution. This allows for a base layer to be drawn quickly with poor resolution for efficiency, and for the resolution to increase as the image is magnified. [1]

Quantile Classification - Divides the data into groups with the same number of values for each group.

Query - A method for selecting features or records in a database that match a desired criteria.

Raster Calculator - Tool for performing mathematical calculations. Inputs may include numbers, tables, shapefiles, raster layers, and raster datasets. [1]

Raster Data Model - A grid representation of the world typically used to store continuous data (e.g., a satellite image or aerial photograph). [1]

Record - A set of related data containing all attributes for an individual feature (typically a row in a database). [1]

Remote Sensing - Technique used to gather information about the environment or an object from a distance. Examples include aerial and satellite photography.

Scale - Ratio or relationship between the size of an area on the ground and its representation on a map. [1]

Scale Bar - A graphical element on a map showing the relationship between the actual distance on Earth and the distance on a map.

Script - Set of instructions executed by a computer program. Also one of the 5 types of documents contained in a program file.

Select Features - Tool that allows the user to select particular features that can then be examined in the attribute table.

shapefile - Data storage format that contains the attributes of particular vector (i.e., point, line, polygon) features. [1]

Sketch Tool - Tool that allows the user to edit a feature by adding points, vertices, or segments. [1]

Snapping Environment - Defines when snapping will occur, and how features relate to each other. Snapping allows new features to relate to existing features in the same or different layers.

Statistics - Study of mathematics dealing with the collection, analysis, and interpretation of numerical data.

Table - Data arranged in rows and columns. Each row is a single record and each column is a field.

Text - Words, letters, or symbols typed on the computer.

Thematic Map - A map that portrays attributes of geographic features as patterns, such as population density or rainfall.

Toolbar - Set of buttons that can be clicked on to activate certain commands in the software program.

Undo - Tool that removes the last step or operation performed.

Universal Trans Mercator (UTM) - A projected coordinate system based on the metric system that divides the world into 60 north and south zones each 6° wide. [1]

Waypoint - A particular location represented in latitude-longitude coordinates. [1]

X, Y Coordinates - The distance from an origin (0, 0) represented as a pair of values along two axes. The “x” coordinate represents the distance along the horizontal axis, and the “y” coordinate represents the distance along the vertical axis.

Zoom - Used to view a larger or smaller region of an image or a map on the screen.

Sources:

[1] ESRI, "GIS Dictionary", 30 September 2015. [Online]. Available: http://support.esri.com/en/knowledgebase/GISDictionary/search. [Accessed 30 September 2015].

[2] NASA, "Earth Observatory Glossary," 30 September 2015. [Online]. Available: http://earthobservatory.nasa.gov/Glossary/index.php?mode=all. [Accessed 30 September 2015].



Remote Sensing Terms

Absorption - The process by which a substance retains radiant energy. [1]

Active Sensor - A sensor that actively transmits radiation and records radiation that is reflected or transmitted back from objects (e.g., Radar). [1]

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) - Part of NASA’s Earth Observing System (EOS) and onboard the Terra platform, ASTER is an instrument that collects data about land surface temperature, reflectance, elevation, and emissivity. [1]

Advanced Very High Resolution Radiometer (AVHRR) - Instrument used for determining surface temperature and cloud cover with visible and infrared detectors. [1]

Aerosol - Liquid or solid particles suspended in a gas.

Albedo - A ratio of solar radiation reflected by a surface to the amount of incoming solar radiation striking that surface. [1]

Anomaly - The deviation of a measurement (typically precipitation or temperature) within a given area and specific time period from a historic temporal or spatial average in the same area. [1]

Apogee - The location at which a satellite is farthest from the Earth’s surface when in an elliptical orbit. [1]

Ascending Node - The longitudinal point at which a satellite crosses from south to north across the equatorial plane. See also Descending Node. [1]

Astronomical Unit (AU) - The distance between the sun and the earth (approximately 149,500,000 kilometers on average). [1]

Atmosphere - The layers of air surrounding the earth (troposphere, stratosphere, mesosphere, thermosphere, and exosphere). [1]

Azimuth - The angular distance from a fixed point measured clockwise from north where north is typically 0°, east is 90°, south is 180°, and west is 270°. It is also often expressed as the angle of the light source (e.g. the sun).

Backscatter - The reflection of energy from the sun away from the Earth’s surface by clouds. [1]

Band - Regions of the electromagnetic spectrum recorded by a remote sensor.

Blackbody - A surface from which no energy is transmitted or reflected (i.e., all incident radiation is absorbed) [1]

Brightness Temperature - The intensity of thermal radiation emitted by an object expressed in temperature units. [1]

Canopy - A layer formed by the branches and/or leaves of vegetation.

Clouds and the Earth’s Radiant Energy System (CERES) - A satellite instrument measuring the Earth-emitted and solar-reflected radiation from the Earth’s surface to the top of the atmosphere. [1]

Declination - Angular distance to a satellite from the equator. [1]

Descending Node - The point at which a satellite crosses from north to south across the equatorial plane. See also Ascending Node. [1]

Digital Elevation Model (DEM) - A digital representation of the Earth’s topography.

Diurnal - Daily (i.e., every 24 hours).

Doppler Effect - Description of the way in which sound and light waves appear to change in frequency depending on the velocity of the source and/or the receiver of a signal. [1]

Earth Observing System (EOS) - A series of NASA spacecraft designed to collect data used in the study of global climate change. [1]

Earth Science Enterprise (ESE) - An international effort to record and interpret data about the Earth’s environment. [1]

Electromagnetic Radiation - All energy moving at the speed of light in equally spaced repetitive waves. Examples include gamma rays, infrared, radio waves, and visible light. [2]

Electromagnetic Spectrum - Categorization of solar radiation constituting the entire range of electromagnetic radiation. [1] [2]

Elevation - The angle at which an antenna must be oriented in order to (optimally) receive signals from a spacecraft. [1]

Emissivity - A ratio of emitted radiation from a surface to the radiation emitted from a blackbody (while at the same temperature). [1]

Enhanced Thematic Mapper Plus (ETM+) - Multispectral sensor on the Landsat 7 satellite that provides high resolution image data of the Earth’s surface. [1]

False Color - An image processing technique in which image colors viewed do not correspond to those as seen by the human eye (i.e., natural color).

Far Infrared - Electromagnetic radiation with wavelengths between approximately 25 µm and 1000 µm. [1]

Fraction of Photosynthetically Active Radiation (FPAR) - Radiation used by photosynthetically active vegetation (between 400 and 700 nm). [1]

General Circulation Model (GCM) - A computer model of the Earth’s climate system used to investigate human-induced climate change. [1]

Geographic Information Systems (GIS) - Computer-based methods of recording, analyzing, and displaying geographic information, able to link data typically found on maps (roads, rivers, boundaries) with observations typically not conveyed through maps such as population, vegetation type, etc.

Geostationary - A satellite orbit in which the position of the satellite remains stationary with respect to the rotation of the Earth. [1]

Geosynchronous - Synchronized with the Earth’s rotation. See also Geostationary. [1]

Global Positioning System (GPS) - System of satellites used to compute the positions of objects on earth.

Hemisphere - Half of a sphere, most commonly used to describe half of the earth as in the northern hemisphere (north of the equator), southern hemisphere (south of the equator), eastern hemisphere (east of the prime meridian), or the western hemisphere (west of the prime meridian).

High-Resolution Infrared Radiation Sounder (HIRS) - Satellite instrument used to create a vertical temperature profile from the surface of the Earth to approximately 40 km altitude. [1]

Hyperspectral - Refers to a sensor, or imagery from a sensor that records data for hundreds to thousands of electromagnetic energy wavelengths. [1]

Infrared Radiation (IR) - Electromagnetic radiation with wavelengths longer than visible radiation and shorter than microwave radiation (approximately 0.7 µm to 1000 µm). Remote sensing techniques can use infrared radiation to measure physical/chemical properties of surfaces (e.g., vegetation cover, chemical composition of surfaces) [1]

Insolation - Amount of incident solar radiation per unit of horizontal surface. [1]

Isothermal - Equal in temperature.

Land Cover – A land surface’s characteristics derived from its spectral signature (i.e., information about how it absorbs and reflects light energy). [1]

Landsat – Land Remote-Sensing Satellite. Created for the systematic collection of data regarding the Earth’s resources. [1]

Latitude - Angular distance north or south of the equator (typically in degrees).

Leaf Area Index (LAI) – Area of vegetation foliage pare unit ground area.

Lidar – Light Detection and Ranging. A technique in remote sensing for measuring distance by active illumination of a target with a laser and subsequent analysis of reflected light energy.

Longitude - Angular distance east or west of the Greenwich prime meridian (in England). All longitudinal lines pass through the North and south Poles.

Metadata – Commonly thought of as ‘data about the data’. Metadata typically provide information about the content of a data set, and when, where and how it was collected.

Micrometer (µm) - One millionth of a meter.

Microwave - Electromagnetic radiation with wavelengths ranging from approximately 1000 µm to 1 m. [1]

Middle Infrared - Electromagnetic radiation with wavelengths ranging from approximately 2 µm to 5 µm. [1]

Moderate Resolution Imaging Spectroradiometer (MODIS) - Sensor onboard the Terra and Aqua satellites viewing the entire Earth’s surface every one to two days with 36 spectral bands at a moderate spatial resolution. [1]

Nadir - Refers to the point on the Earth’s surface directly beneath a satellite. [1]

Nanometer (nm) - One billionth of a meter.

NASA - National Aeronautics and Space Administration.

Near Infrared - electromagnetic radiation with wavelengths ranging from approximately 0.7 µm to 2 µm. [1]

Net Primary Production (NPP) – The amount of new plant material produced annually per unit ground area.

Normalized Difference Vegetation Index (NDVI) - Index of vegetation health calculated as a ratio of the difference between near infrared light and red light reflected by surface divided by the sum of near infrared light and red light reflected by the same surface. [1]


Obliquity - Refers to how much the earth is “tilted”. [1]

Panchromatic - Black and white (greyscale) imagery.

Parameter - A constant in an expression (i.e., a function or an equation). The values a parameter takes determine the specific characteristics of the given expression. [1]

Passive System - A system that captures radiation emitted from a surface or radiation reflected from a surface but emitted from something other than the system itself. See also Active System. [1]

Period - The time it takes for satellite to complete a full orbit of the Earth. [1]

Photosynthesis - The process by which green vegetation synthesizes organic compounds by capturing light as an energy source.

Photosynthetically Active Radiation (PAR) - Portion of the electromagnetic spectrum used by plants in photosynthesis.

Pixel - Smallest unit of information in an image. Higher resolution images will have a larger number of pixels than lower resolution images.

Platform - A satellite carrying instruments. [1]

Polar Orbit - An orbit where a satellite will cross both polar regions once per orbit. [1]

Primary Productivity - Rate of biomass increase in plants via photosynthesis.

Radiation - A form of energy transfer in which energy is released as energy is absorbed by an object. [1]

Reflection - The process in which waves (i.e., sound or light waves) are returned from a surface. [1]

Remote Sensing - Technique used to gather information about the environment or an object from a distance. Examples include aerial and satellite photography.

Resolution - In remote-sensing, refers to the ground area represented by a pixel in an image.

Satellite - An object orbiting the sun, or a planet.

Scattering - The redirection of electromagnetic radiation as it encounters molecules in the atmosphere, ocean or surface of the Earth. [1]

Scene - The physical space from which information is captured by sensor. [1]

Sensible Heat - Radiative energy from the Earth’s surface to the atmosphere through various processes (i.e., conduction, advection, and convection). [1]

Sensor - An instrument that provides some form of output (typically an electrical signal) in response to some form of stimulus (e.g., radiation striking the sensor). [1]

Shortwave Radiation - Also referred to as “solar radiation”, this term refers to radiation from the sun with approximate wavelengths of less than 4 µm. [1]

Shuttle Radar Topography Mission (SRTM) - A NASA space shuttle mission acquiring topographic data for the majority of the Earth’s land surface . [1]

Solar Radiation - Energy from the sun.

Spectral Band - Refers to discrete sections of the electromagnetic spectrum. [1]

Spectral Signature - Visualization (e.g., a graph) of the variation in absorbed or reflected electromagnetic radiation.

Sun-synchronous - A satellite orbit providing consistent light on the Earth. [1]

Swath - The area a satellite observes in its orbit around the Earth. [1]

Thematic Mapper (TM) - A Landsat scanner capturing multispectral data for the Earth’s surface. [1]

Thermal Infrared - Electromagnetic radiation with wavelengths of approximately 3 µm to 25 µm. [1]

Topography - A graphical representation on a map of physical features within a region of interest. [1]

Ultraviolet Radiation - A range of electromagnetic radiation mostly blocked by the Earth’s atmosphere with wavelengths slightly beyond the violet end of the visible spectrum. [1]

USGS - United States Geological Survey.

Visible - Portion of the electromagnetic spectrum visible to the human eye (approximately 0.4 µm to 0.7 µm). [1]

Wavelength - The physical distance for one wave to repeat (i.e., the distance between successive peaks of a wave). [1]

X-ray - Electromagnetic radiation with wavelengths of approximately 0.00001 Å to 3000 Å. [1]


Sources:

[1] NASA, "Earth Observatory Glossary," 30 September 2015. [Online]. Available: http://earthobservatory.nasa.gov/Glossary/index.php?mode=all. [Accessed 30 September 2015].

[2] S. Khorram, F. H. Koch, C. F. van der Wiele and S. A. C. Nelson, Remote Sensing, J. N. Pelton, Ed., New York Heidelberg Dordrect London: Springer, 2012.

[3] ESRI, "GIS Dictionary," 30 September 2015. [Online]. Available: http://support.esri.com/en/knowledgebase/GISDictionary/search.