“Hyperspectral remote sensing is the definitive optical tool for increasing knowledge and understanding of the Earth's surface. Contiguous high-resolution spectrometry provides a new dimension in mapping capability because of the potential for quantitative measurement of surface biogeochemistry.” (John S. MacDonald, Susan L. Ustin, and Michael E. Schaepman. “The Contributions of Dr. Alexander F. H. Goetz to Imaging Spectroscopy.” Remote Sensing of Environment. September 2009: S2-S4.)
Multispectral remote sensing involves the acquisition of visible, near infrared, and short-wave infrared images in several broad wavelength bands. Different materials reflect and absorb differently at different wavelengths. As such, it is possible to differentiate among materials by their spectral reflectance signatures as observed in these remotely sensed images, whereas direct identification is usually not possible. NASA’s Landsat, one of the more common multispectral imagers, is widely used for monitoring a wide range of landscape scale properties.
Hyperspectral imaging systems acquire images in over one hundred contiguous spectral bands. While multispectral imagery is useful to discriminate land surface features and landscape patterns, hyperspectral imagery allows for identification and characterization of materials. In addition to mapping distribution of materials, assessment of individual pixels is often useful for detecting unique objects in the scene.
Well developed scientific application areas include geology and mineral exploration; forestry; marine, coastal zone, inland waters and wetlands; agriculture; ecology; urban; snow and ice; and atmosphere. There are also numerous military applications in camouflage, littoral zone mapping, and landmine detection. Hyperspectral sensors pose an advantage over multispectral sensors in their ability to identify and quantify molecular absorption. The high spectral resolution of a hyperspectral imager allows for detection, identification and quantification of surface materials, as well as inferring biological and chemical processes.
For all of these applications, ground truth signatures collected in the field and indexed in spectral libraries are critical for many methods of analysis. While image processing packages often include basic spectral libraries, application distinct libraries containing spectra of the specific materials occurring in the target field area greatly improves the accuracy of generated interpretations. In particular, spectra of vegetation are influenced by such a wide range of environmental conditions that it makes it difficult to adequately represent this variability without the collection of site specific field spectra.
The ASD FieldSpec® line of spectroradiometers offers multiple configuration options and the industry’s fastest sampling speeds. The use of a flexible fiber optic cable and a wide range of foreoptics, along with several direct sampling accessories, give you a number of options for acquiring the best data possible. Bringing a level of device portability that only ASD can provide and combined with GPS compatibility, the FieldSpec instruments help make it possible for you to work in some of the most remote geographic regions of the planet.
Examples of research utilizing ASD instrumentation can be found in the links below.
Kilauea Volcano, Hawaii
CLAMS - Cheasapeake Lighthouse & Aircraft Measurements for Satellites July 10 - August 2/2001
In-flight Radiometric and Spatial Calibration of EO-1 Optical Sensors
Changes in Biogeochemical Cycles NASA-Earth Observing System NAG5-6137
Use of Scanning Infrared Surface Temperature Radiometer (SISTeR)
Additional spectral remote sensing for hyperspectral and multispectral imagery analysis research applications are also available under the Application Notes tab at the top of this page.