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Glossary

General
Platforms
Sensors
NASA Centers
Links to other sources

More extensive glossary, unsorted and yet to be integrated with this list.

General

Remote Sensing

Data gathering by a sensor that is not in the immediate vicinity of the object sensed.  RS usually refers to photography by satellites or aircraft, but technically includes video photography, human vision, and non-optical sensing such as household motion detection.

Aerial Photograph, oblique:

A photograph taken with the camera axis directed between the horizontal and the vertical

Stereo Pairs

A pair of photos with overlap in area and are suitable for stereoscopic examination

Platforms

AVHRR

Advanced Very High Resolution Radiometer is a multispectral imaging system carried by the polar-orbiting, crosstrack, multispectral scanner on the TIROS-NOAA series of meteorological satellites acquiring five spectral bands of data (0.55 to 12.50 µm) with a ground resolution 1.1 x 1.1 km

AVIRIS

Airborne Visible Infrared Imaging Spectrometer.  Imaging from high-altitude (U2, about 15 km altitude, 20m resolution) and low-altitude (Twin Otter, 3 km altitude, 4m resolution) aircraft.

IKONOS

A commercial imaging satellite launched by Space Imaging in late 1999.  Output: 1m panchromatic, 4m 4-band multispectral.  The currently functioning satellite is Ikonos-2.  Its predecessor suffered a launch failure.

IRS

Indian Remote Sensing satellite.  Not to be confused with the Internal Revenue Service, the US tax collection agency.

Landsat

Sponsored by the U.S. government, the first Landsat satellite was launched in 1972 with a resolution of approximately 80m. The most recent, Landsat 7, a multispectral sensor, was launched on April 15, 1999 and includes the Enhanced Thematic Mapper Plus (ETM+) with a resolution of approximately 30m.

Quickbird

A pair of commercial imaging satellites, Quickbird-1 and Quickbird-2, to be launched by EarthWatch Inc (Colorado) in late 2000, with output of 1m panchromatic, 4m 4-band multispectral, equivalent to AVIRIS.  Their predecessor, Earlybird, suffered a communications failure shortly after launch in December 1998.

RADARSAT-1

Synthetic Aperture Radar data provided by the Canadian company, Radarsat International, established in 1989.  Specifications include: 7 beam modes with image sizes ranging from 50 x 50 km to 500 x 500 km and resolutions ranging from 8m to 100m

SPOT

Refers to data provided by SPOT Image Corporation , a subsidiary of SPOT Image S.A. The company was established in 1982 and has since launched 4 satellites and provides a variety of data and products from these satellites. Resolution is 20m for multispectral bands and 10m for the panchromatic band.

SRTM

Shuttle Radar Topography Mission is a NASA/NIMA sponsored mission designed to use C-band and X-band interferometric synthetic aperture radars (IFSARs) that acquired topographic data over approximately 80% of Earth's land mass during an 11-day Shuttle mission launched February 11, 2000.

STAR-3i

Intermap Technologies supplies Global Terrain products including Orthorectified images (ORIs) and Digital Elevation Models (DEMs). Their STAR-3i sensor is an Interferometric Synthetic Aperture Radar (INSAR) mounted in a Learjet 36 aircraft that acquires a 10km wide swath of 2.5m resolution radar data

Sensors

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.

Hyperspectral

Modern sensors are capable of capturing separate reflectances over a couple of hundred different wavelengths, so that each pixel is associated with a curve of intensity vs wavelength.  Because of absorption by atmospheric water and dust, not all portions of the spectrum produce good signals.

Multispectral

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.

Panchromatic

Sensing in a single wide band, resulting in high-resolution monochromatic image.  Contrast against multispectral and hyperspectral.

SAR

Synthetic Aperture Radar.  In radar terms, aperture is the band width over which the antenna gathers data.  In general a long radar antenna gathers information over more wavelengths, but is difficult to send into space.  SAR uses the motion of the space platform to simulate antenna length.  An object is imaged while the craft travels about 4 km through space — with a little clever processing of the signals, this displacement of the antenna relative to the object is used to simulate a 4 km long antenna.  The Shuttle Radar Topography Mission is a celebrated example of the application of SAR.  A good introductory resource on SAR is the Alaska SAR facility, http://www.asf.alaska.edu/user_serv/sar_faq.html

NASA Centers

Links

Sources

1. Jeff Hemphill, Remote Sensing Research Unit, UCSB, web site for the class, Aerial Photogrammetry.
2. ERS-1 Calibration and Validation, ESA bulletin no 65, February 1991, by E. Attema and R. Francis.
3. Manual of Remote Sensing, Leonard Bowden, American Society Photogrammetry and Remote Sensing, Falls Church VA, copyright 1975

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