Primer on the Industry

At-Nadir: A point on the ground directly beneath the satellite, at a 90-degree angle above the Earth’s surface.

Change Detection: The sensing of environmental changes that uses two or more scenes covering the same geographic area acquired over a period of time. Change detection is useful for monitoring change associated with urbanization, agricultural development and deforestation.

Color-Infrared Imagery: Also called “false color” imagery, designed to differentiate between colors rather than reproduce them accurately. A tool to study landforms, vegetation health patterns, environmental pollution, and other effects of human activities on the planet’s surface.

DEM - Digital Elevation Model: A three dimensional representation of the Earth's terrain in digital format, used for visualizing and analyzing terrain, calculating land masses and orthorectifying satellite images.

Downlinking: Electronically transmitting data from a satellite to the ground.

GCP - Ground Control Point: A point on the Earth’s surface of known location that is visually observable from either air or space. Used to geo-reference image data sources, such as remotely sensed images or scanned maps.

Geo-Locational Accuracy: The degree to which the coordinates of points determined from a geospatially referenced image or dataset agree with the coordinates determined by ground survey or other independent, higher-accuracy means.

Georeferenced: A satellite image whose geographic coordinates have been matched with known, real-world coordinates.

Geospatial: Pertaining to the geographic location and characteristics of natural or constructed features and boundaries on, above or below the Earth’s surface, especially when referring to data that are geographic and spatial in nature.

GIS - Geographic Information System: A computer-based system for creating and managing spatial data and associated attributes, capable of integrating, storing, editing, analyzing, and displaying geographically referenced information.

GPS - Global Positioning System: A satellite navigation system. A constellation of more than two dozen GPS satellites broadcasting precise timing signals by radio to electronic GPS receivers which allow them to accurately determine their location (longitude, latitude and altitude) in real time, day or night, in any weather, anywhere on Earth.

Multispectral Imagery: Also commonly referred to as “color” imagery. The use of one or more imaging sensors to obtain imagery from different portions of the electromagnetic spectrum.

Natural Color Imagery: A three-band image combining red, green and blue bands of data.

NGA - National Geospatial Intelligence Agency: NGA is a member of the U.S. Intelligence Community and a Department of Defense Combat Support Agency. The organization provides timely, relevant and accurate geospatial intelligence in support of national security objectives.

Off-Nadir: Any point that is not directly below a sensor, but off to an angle in any direction.

Orthorectified Imagery: Imagery from which distortions due to varying elevation, tilt, and surface topography have been removed, so that the image represents every object on the ground as if viewed directly from above.

Panchromatic Imagery: Commonly referred to as black and white or gray-scale imagery.

Pan-Sharpened Imagery: The fusion of panchromatic and multispectral imagery.

Photogrammetry: A measurement technology in which the 3D coordinates of points on an object are determined by measurements made in two or more photographic images taken from different positions.

Radiometric Distortions: Distortions in imagery caused by variations in brightness and reflectance or spectral content.

Raw Data: Unaltered, unprocessed satellite imagery data.

Remote Sensing: 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.

Resolution: Also called spatial resolution, it represents the dimension of the smallest area depicted in the image. Higher resolution means more spatial detail.

Revisit Capability: The frequency with which a satellite is able to fly over the same geographic area to repeatedly capture imagery.

Stereoscopic: 'Solid looking.' Having visible depth as well as height and width. Imagery with three-dimensional characteristics that creates the illusion of depth.

Sun-Synchronous Orbit: A near-polar orbit where the satellite always crosses the equator at the same local solar time.

Swath Width: The cross-track width of an image defined by the camera’s field of view. If the satellite’s swath width is 60 km then a satellite image scene will usually be delivered as a 60 km x 60 km image