Hyperspectral imaging
Encyclopedia
Hyperspectral imaging collects and processes information from across the electromagnetic spectrum
. Much as the human eye
sees visible light in three bands (red, green, and blue), spectral imaging
divides the spectrum into many more bands. This technique of dividing images into bands can be extended beyond the visible.
Humans build sensors and processing systems to provide such capability for application in agriculture, mineralogy, physics, and surveillance. Hyperspectral sensors look at objects using a vast portion of the electromagnetic spectrum. Certain objects leave unique 'fingerprints' across the electromagnetic spectrum. These 'fingerprints' are known as spectral signatures and enable identification of the materials that make up a scanned object. For example, a spectral signature
for oil helps mineralogists find new oil field
s.
Hyperspectral sensors collect information as a set of 'images'. Each image represents a range of the electromagnetic spectrum and is also known as a spectral band. These 'images' are then combined and form a three-dimensional hyperspectral data cube
for processing and analysis.
Hyperspectral cubes are generated from airborne sensors like the NASA's Airborne Visible/Infrared Imaging Spectrometer (AVIRIS), or from satellites like NASA's Hyperion. However, for many development and validation studies, handheld sensors are used.
The precision of these sensors is typically measured in spectral resolution, which is the width of each band of the spectrum that is captured. If the scanner detects a large number of fairly narrow frequency bands, it is possible to identify objects even if they are only captured in a handful of pixels. However, spatial resolution is a factor in addition to spectral resolution. If the pixels are too large, then multiple objects are captured in the same pixel and become difficult to identify. If the pixels are too small, then the energy captured by each sensor cell is low, and the decreased signal-to-noise ratio
reduces the reliability of measured features.
MicroMSI
, Opticks
and Envi
are three remote sensing application
s that support the processing and analysis of hyperspectral data. The acquisition and processing of hyperspectral images is also referred to as imaging spectroscopy
.
Hyperspectral imaging is part of a class of techniques commonly referred to as spectral imaging
or spectral analysis
. Hyperspectral imaging is related to multispectral imaging. The distinction between hyper- and multi-spectral is sometimes based on an arbitrary "number of bands" or on the type of measurement, depending on what is appropriate to the purpose.
Multispectral imaging deals with several images at discrete and somewhat narrow bands. Being "discrete and somewhat narrow" is what distinguishes multispectral in the visible from color photography
. A multispectral sensor may have many bands covering the spectrum from the visible to the longwave infrared. Multispectral images do not produce the "spectrum" of an object. Landsat is an excellent example.
Hyperspectral deals with imaging narrow spectral bands over a continuous spectral range, and produce the spectra of all pixels in the scene. So a sensor with only 20 bands can also be hyperspectral when it covers the range from 500 to 700 nm with 20 bands each 10 nm wide. (While a sensor with 20 discrete bands covering the VIS, NIR, SWIR, MWIR, and LWIR would be considered multispectral.)
'Ultraspectral' could be reserved for interferometer type imaging sensors with a very fine spectral resolution. These sensors often have (but not necessarily) a low spatial resolution of several pixel
s only, a restriction imposed by the high data rate.
. This technology is continually becoming more available to the public. Organizations such as NASA
and the USGS have catalogues of various minerals and their spectral signatures, and have posted them online to make them readily available for researchers.
, work is under way to use imaging spectrometer
s to detect grape variety and develop an early warning system for disease outbreaks. Furthermore, work is underway to use hyperspectral data to detect the chemical composition of plants, which can be used to detect the nutrient and water status of wheat in irrigated systems.
Another application in agriculture is the detection of animal proteins in compound feeds to avoid bovine spongiform encephalopathy (BSE)
, also known as mad-cow disease. Different studies have been done to propose alternative tools to the reference method of detection, (classical microscopy
). One of the first alternatives is near infrared microscopy (NIR), which combines the advantages of microscopy and NIR. In 2004, the first study relating this problem with hyperspectral imaging was published. Hyperspectral libraries that are representative of the diversity of ingredients usually present in the preparation of compound feeds were constructed. These libraries can be used together with chemometric tools to investigate the limit of detection, specificity and reproducibility of the NIR hyperspectral imaging method for the detection and quantification of animal ingredients in feed.
, can be rapidly mapped for nearly all minerals of commercial interest with hyperspectral imaging. Fusion of SWIR and LWIR spectral imaging is standard for the detection of minerals in the feldspar
, silica
, calcite
, garnet
, and olivine
groups, as these minerals have their most distinctive and strongest spectral signature
in the LWIR regions.
Hyperspectral remote sensing
of minerals is well developed. Many minerals can be identified from airborne images, and their relation to the presence of valuable minerals, such as gold and diamonds, is well understood. Currently, progress is towards understanding the relationship between oil and gas leakages from pipelines and natural wells, and their effects on the vegetation and the spectral signatures. Recent work includes the PhD dissertations of Werff and Noomen.
(EDS), electron energy loss spectroscopy
(EELS), infrared spectroscopy
(IR), Raman spectroscopy
, or cathodoluminescence
(CL) spectroscopy, in which the entire spectrum measured at each point is recorded. EELS hyperspectral imaging is performed in a scanning transmission electron microscope (STEM); EDS and CL mapping can be performed in STEM as well, or in a scanning electron microscope
or electron microprobe
(also called an electron probe microanalyzer or EPMA). Often, multiple techniques (EDS, EELS, CL) are used simultaneously.
In a "normal" mapping experiment, an image of the sample is simply the intensity of a particular emission mapped in an XY raster. For example, an EDS map could be made of a steel
sample, in which iron
X-ray
intensity is used for the intensity grayscale of the image. Dark areas in the image would indicate non-iron-bearing impurities. This could potentially give misleading results; if the steel contained tungsten
inclusions, for example, the high atomic number of tungsten could result in bremsstrahlung
radiation that would make the iron-free areas appear to be rich in iron.
By hyperspectral mapping, instead, the entire spectrum at each mapping point is acquired, and a quantitative analysis can be performed by computer postprocessing of the data, and a quantitative map of iron content produced. This would show which areas contained no iron, despite the anomalous X-ray counts caused by bremsstrahlung. Because EELS core-loss edges are small signals on top of a large background, hyperspectral imaging allows large improvements to the quality of EELS chemical maps.
Similarly, in CL mapping, small shifts in the peak emission energy could be mapped, which would give information regarding slight chemical composition changes or changes in the stress state of a sample.
purposes. Hyperspectral imaging is particularly useful in military surveillance because of countermeasure
s that military entities now take to avoid airborne surveillance. Aerial surveillance was used by French soldiers using tethered balloons to spy on troop movements during the French Revolutionary Wars, and since that time, soldiers have learned not only to hide from the naked eye, but also to mask their heat signature
s to blend in to the surroundings and avoid infrared scanning. The idea that drives hyperspectral surveillance is that hyperspectral scanning draws information from such a large portion of the light spectrum that any given object should have a unique spectral signature
in at least a few of the many bands that are scanned. The soldiers from NSWDG who killed Osama bin Laden
in May of 2011 used this technology while conducting the raid
(Operation Neptune's Spear) on Osama bin Laden's compound in Abbottabad
, Pakistan
.
Traditionally, commercially available thermal infrared hyperspectral imaging systems have needed liquid nitrogen
or helium
cooling, which has made them impractical for most surveillance applications. In 2010, Specim
introduced a thermal infrared hyperspectral camera that can be used for outdoor surveillance and UAV applications without an external light source such as the sun or the moon.
The primary disadvantages are cost and complexity. Fast computers, sensitive detectors, and large data storage capacities are needed for analyzing hyperspectral data. Significant data storage capacity is necessary since hyperspectral cubes are large, multidimensional datasets, potentially exceeding hundreds of megabytes. All of these factors greatly increase the cost of acquiring and processing hyperspectral data. Also, one of the hurdles researchers have had to face is finding ways to program hyperspectral satellites to sort through data on their own and transmit only the most important images, as both transmission and storage of that much data could prove difficult and costly. As a relatively new analytical technique, the full potential of hyperspectral imaging has not yet been realized.
Electromagnetic spectrum
The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object....
. Much as the human eye
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...
sees visible light in three bands (red, green, and blue), spectral imaging
Spectral imaging
Spectral imaging is a branch of spectroscopy and of photography in which a complete spectrum or some spectral information is collected at every location in an image plane...
divides the spectrum into many more bands. This technique of dividing images into bands can be extended beyond the visible.
Humans build sensors and processing systems to provide such capability for application in agriculture, mineralogy, physics, and surveillance. Hyperspectral sensors look at objects using a vast portion of the electromagnetic spectrum. Certain objects leave unique 'fingerprints' across the electromagnetic spectrum. These 'fingerprints' are known as spectral signatures and enable identification of the materials that make up a scanned object. For example, a spectral signature
Spectral signature
Spectral Signatures are the specific combination of reflected and absorbed electromagnetic radiation at varying wavelengths which can uniquely identify an object. The spectral signature of stars indicates the spectrum according to the EM spectrum...
for oil helps mineralogists find new oil field
Oil field
An oil field is a region with an abundance of oil wells extracting petroleum from below ground. Because the oil reservoirs typically extend over a large area, possibly several hundred kilometres across, full exploitation entails multiple wells scattered across the area...
s.
Acquisition and analysis
Data cube
In computer programming contexts, a data cube is a three- dimensional array of values, commonly used to describe a time series of image data...
for processing and analysis.
Hyperspectral cubes are generated from airborne sensors like the NASA's Airborne Visible/Infrared Imaging Spectrometer (AVIRIS), or from satellites like NASA's Hyperion. However, for many development and validation studies, handheld sensors are used.
The precision of these sensors is typically measured in spectral resolution, which is the width of each band of the spectrum that is captured. If the scanner detects a large number of fairly narrow frequency bands, it is possible to identify objects even if they are only captured in a handful of pixels. However, spatial resolution is a factor in addition to spectral resolution. If the pixels are too large, then multiple objects are captured in the same pixel and become difficult to identify. If the pixels are too small, then the energy captured by each sensor cell is low, and the decreased signal-to-noise ratio
Signal-to-noise ratio
Signal-to-noise ratio is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined as the ratio of signal power to the noise power. A ratio higher than 1:1 indicates more signal than noise...
reduces the reliability of measured features.
MicroMSI
MicroMSI
MicroMSI for Windows is a remote sensing imagery analysis program designed for use in introductory courses in remote sensing, developed by the National Geospatial-Intelligence Agency...
, Opticks
Opticks (software)
Opticks is an open source, remote sensing application that supports imagery, video , Synthetic Aperture Radar , multi-spectral, hyper-spectral, and other types of remote sensing data. Opticks is unlike other remote sensing applications because it treats imagery and video alike...
and Envi
Envi
Envi or ENVI may refer to:* Committee on the Environment, Public Health and Food Safety * Envi , a defunct Chrysler division to develop hybrid and full electric vehicles....
are three remote sensing application
Remote sensing application
A remote sensing application is a software application that processes remote sensing data. Remote sensing applications are similar to graphics software, but they enable generating geographic information from satellite and airborne sensor data. Remote sensing applications read specialized file...
s that support the processing and analysis of hyperspectral data. The acquisition and processing of hyperspectral images is also referred to as imaging spectroscopy
Imaging spectroscopy
Imaging spectroscopy is similar to color photography, but each pixel acquires many bands of light intensity data from the spectrum, instead of just the three bands of the RGB color model...
.
Differences between hyperspectral and multispectral imaging
Spectral imaging
Spectral imaging is a branch of spectroscopy and of photography in which a complete spectrum or some spectral information is collected at every location in an image plane...
or spectral analysis
Spectral analysis
Spectral analysis or Spectrum analysis may refer to:* Spectrum analysis in chemistry and physics, a method of analyzing the chemical properties of matter from bands in their visible spectrum...
. Hyperspectral imaging is related to multispectral imaging. The distinction between hyper- and multi-spectral is sometimes based on an arbitrary "number of bands" or on the type of measurement, depending on what is appropriate to the purpose.
Multispectral imaging deals with several images at discrete and somewhat narrow bands. Being "discrete and somewhat narrow" is what distinguishes multispectral in the visible from color photography
Color photography
Color photography is photography that uses media capable of representing colors, which are traditionally produced chemically during the photographic processing phase...
. A multispectral sensor may have many bands covering the spectrum from the visible to the longwave infrared. Multispectral images do not produce the "spectrum" of an object. Landsat is an excellent example.
Hyperspectral deals with imaging narrow spectral bands over a continuous spectral range, and produce the spectra of all pixels in the scene. So a sensor with only 20 bands can also be hyperspectral when it covers the range from 500 to 700 nm with 20 bands each 10 nm wide. (While a sensor with 20 discrete bands covering the VIS, NIR, SWIR, MWIR, and LWIR would be considered multispectral.)
'Ultraspectral' could be reserved for interferometer type imaging sensors with a very fine spectral resolution. These sensors often have (but not necessarily) a low spatial resolution of several pixel
Pixel
In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....
s only, a restriction imposed by the high data rate.
Applications
Hyperspectral remote sensing is used in a wide array of applications. Although originally developed for mining and geology (the ability of hyperspectral imaging to identify various minerals makes it ideal for the mining and oil industries, where it can be used to look for ore and oil), it has now spread into fields as widespread as ecology and surveillance, as well as historical manuscript research, such as the imaging of the Archimedes PalimpsestArchimedes Palimpsest
The Archimedes Palimpsest is a palimpsest on parchment in the form of a codex. It originally was a copy of an otherwise unknown work of the ancient mathematician, physicist, and engineer Archimedes of Syracuse and other authors, which was overwritten with a religious text.Archimedes lived in the...
. This technology is continually becoming more available to the public. Organizations such as NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
and the USGS have catalogues of various minerals and their spectral signatures, and have posted them online to make them readily available for researchers.
Agriculture
Although the cost of acquiring hyperspectral images is typically high, for specific crops and in specific climates, hyperspectral remote sensing use is increasing for monitoring the development and health of crops. In AustraliaAustralia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, work is under way to use imaging spectrometer
Imaging spectrometer
An imaging spectrometer is an instrument used in hyperspectral imaging and imaging spectroscopy to acquire a spectrally-resolved image of an object or scene, often referred to as a datacube due to the three-dimensional representation of the data. Namely, two axes of the image corresponds to...
s to detect grape variety and develop an early warning system for disease outbreaks. Furthermore, work is underway to use hyperspectral data to detect the chemical composition of plants, which can be used to detect the nutrient and water status of wheat in irrigated systems.
Another application in agriculture is the detection of animal proteins in compound feeds to avoid bovine spongiform encephalopathy (BSE)
Bovine spongiform encephalopathy
Bovine spongiform encephalopathy , commonly known as mad-cow disease, is a fatal neurodegenerative disease in cattle that causes a spongy degeneration in the brain and spinal cord. BSE has a long incubation period, about 30 months to 8 years, usually affecting adult cattle at a peak age onset of...
, also known as mad-cow disease. Different studies have been done to propose alternative tools to the reference method of detection, (classical microscopy
Microscopy
Microscopy is the technical field of using microscopes to view samples and objects that cannot be seen with the unaided eye...
). One of the first alternatives is near infrared microscopy (NIR), which combines the advantages of microscopy and NIR. In 2004, the first study relating this problem with hyperspectral imaging was published. Hyperspectral libraries that are representative of the diversity of ingredients usually present in the preparation of compound feeds were constructed. These libraries can be used together with chemometric tools to investigate the limit of detection, specificity and reproducibility of the NIR hyperspectral imaging method for the detection and quantification of animal ingredients in feed.
Mineralogy
Geological samples, such as drill coresCore sample
A core sample is a cylindrical section of a naturally occurring substance. Most core samples are obtained by drilling with special drills into the substance, for example sediment or rock, with a hollow steel tube called a core drill. The hole made for the core sample is called the "core hole". A...
, can be rapidly mapped for nearly all minerals of commercial interest with hyperspectral imaging. Fusion of SWIR and LWIR spectral imaging is standard for the detection of minerals in the feldspar
Feldspar
Feldspars are a group of rock-forming tectosilicate minerals which make up as much as 60% of the Earth's crust....
, silica
Silicon dioxide
The chemical compound silicon dioxide, also known as silica , is an oxide of silicon with the chemical formula '. It has been known for its hardness since antiquity...
, calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
, garnet
Garnet
The garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives. The name "garnet" may come from either the Middle English word gernet meaning 'dark red', or the Latin granatus , possibly a reference to the Punica granatum , a plant with red seeds...
, and olivine
Olivine
The mineral olivine is a magnesium iron silicate with the formula 2SiO4. It is a common mineral in the Earth's subsurface but weathers quickly on the surface....
groups, as these minerals have their most distinctive and strongest spectral signature
Spectral signature
Spectral Signatures are the specific combination of reflected and absorbed electromagnetic radiation at varying wavelengths which can uniquely identify an object. The spectral signature of stars indicates the spectrum according to the EM spectrum...
in the LWIR regions.
Hyperspectral remote sensing
Remote sensing
Remote sensing is the acquisition of information about an object or phenomenon, without making physical contact with the object. In modern usage, the term generally refers to the use of aerial sensor technologies to detect and classify objects on Earth by means of propagated signals Remote sensing...
of minerals is well developed. Many minerals can be identified from airborne images, and their relation to the presence of valuable minerals, such as gold and diamonds, is well understood. Currently, progress is towards understanding the relationship between oil and gas leakages from pipelines and natural wells, and their effects on the vegetation and the spectral signatures. Recent work includes the PhD dissertations of Werff and Noomen.
Physics
Physicists use an electron microscopy technique that involves microanalysis using either energy-dispersive X-ray spectroscopyEnergy-dispersive X-ray spectroscopy
Energy-dispersive X-ray spectroscopy is an analytical technique used for the elemental analysis or chemical characterization of a sample. It relies on the investigation of an interaction of a some source of X-ray excitation and a sample...
(EDS), electron energy loss spectroscopy
Electron energy loss spectroscopy
In electron energy loss spectroscopy a material is exposed to a beam of electrons with a known, narrow range of kinetic energies. Some of the electrons will undergo inelastic scattering, which means that they lose energy and have their paths slightly and randomly deflected...
(EELS), infrared spectroscopy
Infrared spectroscopy
Infrared spectroscopy is the spectroscopy that deals with the infrared region of the electromagnetic spectrum, that is light with a longer wavelength and lower frequency than visible light. It covers a range of techniques, mostly based on absorption spectroscopy. As with all spectroscopic...
(IR), Raman spectroscopy
Raman spectroscopy
Raman spectroscopy is a spectroscopic technique used to study vibrational, rotational, and other low-frequency modes in a system.It relies on inelastic scattering, or Raman scattering, of monochromatic light, usually from a laser in the visible, near infrared, or near ultraviolet range...
, or cathodoluminescence
Cathodoluminescence
Cathodoluminescence is an optical and electrical phenomenon whereby a beam of electrons is generated by an electron gun and then impacts on a luminescent material such as a phosphor, causing the material to emit visible light. The most common example is the screen of a television...
(CL) spectroscopy, in which the entire spectrum measured at each point is recorded. EELS hyperspectral imaging is performed in a scanning transmission electron microscope (STEM); EDS and CL mapping can be performed in STEM as well, or in a scanning electron microscope
Scanning electron microscope
A scanning electron microscope is a type of electron microscope that images a sample by scanning it with a high-energy beam of electrons in a raster scan pattern...
or electron microprobe
Electron microprobe
An electron microprobe , also known as an electron probe microanalyzer or electron micro probe analyzer , is an analytical tool used to non-destructively determine the chemical composition of small volumes of solid materials...
(also called an electron probe microanalyzer or EPMA). Often, multiple techniques (EDS, EELS, CL) are used simultaneously.
In a "normal" mapping experiment, an image of the sample is simply the intensity of a particular emission mapped in an XY raster. For example, an EDS map could be made of a steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
sample, in which iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
intensity is used for the intensity grayscale of the image. Dark areas in the image would indicate non-iron-bearing impurities. This could potentially give misleading results; if the steel contained tungsten
Tungsten
Tungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as...
inclusions, for example, the high atomic number of tungsten could result in bremsstrahlung
Bremsstrahlung
Bremsstrahlung is electromagnetic radiation produced by the deceleration of a charged particle when deflected by another charged particle, typically an electron by an atomic nucleus. The moving particle loses kinetic energy, which is converted into a photon because energy is conserved. The term is...
radiation that would make the iron-free areas appear to be rich in iron.
By hyperspectral mapping, instead, the entire spectrum at each mapping point is acquired, and a quantitative analysis can be performed by computer postprocessing of the data, and a quantitative map of iron content produced. This would show which areas contained no iron, despite the anomalous X-ray counts caused by bremsstrahlung. Because EELS core-loss edges are small signals on top of a large background, hyperspectral imaging allows large improvements to the quality of EELS chemical maps.
Similarly, in CL mapping, small shifts in the peak emission energy could be mapped, which would give information regarding slight chemical composition changes or changes in the stress state of a sample.
Surveillance
Hyperspectral surveillance is the implementation of hyperspectral scanning technology for surveillanceSurveillance
Surveillance is the monitoring of the behavior, activities, or other changing information, usually of people. It is sometimes done in a surreptitious manner...
purposes. Hyperspectral imaging is particularly useful in military surveillance because of countermeasure
Countermeasure
A countermeasure is a measure or action taken to counter or offset another one. As a general concept it implies precision, and is any technological or tactical solution or system designed to prevent an undesirable outcome in the process...
s that military entities now take to avoid airborne surveillance. Aerial surveillance was used by French soldiers using tethered balloons to spy on troop movements during the French Revolutionary Wars, and since that time, soldiers have learned not only to hide from the naked eye, but also to mask their heat signature
Infrared signature
The term infrared signature is used by defense scientists and the military to describe the appearance of objects to infrared sensors. An infrared signature depends on many factors, including the shape and size of the object, temperature and emissivity, reflection of external sources from the...
s to blend in to the surroundings and avoid infrared scanning. The idea that drives hyperspectral surveillance is that hyperspectral scanning draws information from such a large portion of the light spectrum that any given object should have a unique spectral signature
Spectral signature
Spectral Signatures are the specific combination of reflected and absorbed electromagnetic radiation at varying wavelengths which can uniquely identify an object. The spectral signature of stars indicates the spectrum according to the EM spectrum...
in at least a few of the many bands that are scanned. The soldiers from NSWDG who killed Osama bin Laden
Osama bin Laden
Osama bin Mohammed bin Awad bin Laden was the founder of the militant Islamist organization Al-Qaeda, the jihadist organization responsible for the September 11 attacks on the United States and numerous other mass-casualty attacks against civilian and military targets...
in May of 2011 used this technology while conducting the raid
Death of Osama bin Laden
Osama bin Laden, then head of the Islamist militant group al-Qaeda, was killed in Pakistan on May 2, 2011, shortly after 1 a.m. local time by a United States special forces military unit....
(Operation Neptune's Spear) on Osama bin Laden's compound in Abbottabad
Osama bin Laden's compound in Abbottabad
Osama bin Laden's compound, known locally as the Waziristan Haveli , is the safe house in which Osama bin Laden was hiding when he was killed. The structure is located at the end of a dirt road in Abbottabad, Pakistan. About 35 Miles north of the capital, Islamibad, and just 0.8 miles southwest of...
, Pakistan
Pakistan
Pakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...
.
Traditionally, commercially available thermal infrared hyperspectral imaging systems have needed liquid nitrogen
Liquid nitrogen
Liquid nitrogen is nitrogen in a liquid state at a very low temperature. It is produced industrially by fractional distillation of liquid air. Liquid nitrogen is a colourless clear liquid with density of 0.807 g/mL at its boiling point and a dielectric constant of 1.4...
or helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
cooling, which has made them impractical for most surveillance applications. In 2010, Specim
Specim
Specim, Spectral Imaging Ltd is a European technology firm headquartered in Oulu, Finland. Specim manufactures and sells hyperspectral cameras and systems...
introduced a thermal infrared hyperspectral camera that can be used for outdoor surveillance and UAV applications without an external light source such as the sun or the moon.
Advantages and disadvantages
The primary advantage to hyperspectral imaging is that, because an entire spectrum is acquired at each point, the operator needs no prior knowledge of the sample, and postprocessing allows all available information from the dataset to be mined. Hyperspectral imaging can also take advantage of the spatial relationships among the different spectra in a neighbourhood, allowing more elaborate spectral-spatial models for a more accurate segmentation and classification of the image.The primary disadvantages are cost and complexity. Fast computers, sensitive detectors, and large data storage capacities are needed for analyzing hyperspectral data. Significant data storage capacity is necessary since hyperspectral cubes are large, multidimensional datasets, potentially exceeding hundreds of megabytes. All of these factors greatly increase the cost of acquiring and processing hyperspectral data. Also, one of the hurdles researchers have had to face is finding ways to program hyperspectral satellites to sort through data on their own and transmit only the most important images, as both transmission and storage of that much data could prove difficult and costly. As a relatively new analytical technique, the full potential of hyperspectral imaging has not yet been realized.
See also
- Airborne Real-time Cueing Hyperspectral Enhanced ReconnaissanceAirborne Real-time Cueing Hyperspectral Enhanced ReconnaissanceThe Airborne Real-time Cueing Hyperspectral Enhanced Reconnaissance, also known by the acronym ARCHER, is an aerial imaging system that produces ground images far more detailed than plain sight or ordinary aerial photography can....
- Full spectral imagingFull Spectral ImagingFull spectral imaging is a form of Imaging spectroscopy and is the successor to Hyperspectral imaging. Full Spectral Imaging was developed to improve the capabilities of Earth remote sensing . Hyperspectral imaging acquires data as many contiguous spectral bands. Full Spectral Imaging acquires...
- Multispectral image
- Metamerism (color)Metamerism (color)In colorimetry, metamerism is the matching of apparent color of objects with different spectral power distributions. Colors that match this way are called metamers....
, the perceptual equivalence that hyperspectral imaging overcomes - Chemical imagingChemical imagingChemical imaging is the analytical capability to create a visual image of components distribution from simultaneous measurement of spectra and spatial, time informations....
- Remote sensingRemote sensingRemote sensing is the acquisition of information about an object or phenomenon, without making physical contact with the object. In modern usage, the term generally refers to the use of aerial sensor technologies to detect and classify objects on Earth by means of propagated signals Remote sensing...
- Sensor fusionSensor fusionSensor fusion is the combining of sensory data or data derived from sensory data from disparate sources such that the resulting information is in some sense better than would be possible when these sources were used individually...
- ERDAS IMAGINEERDAS IMAGINEERDAS IMAGINE is a remote sensing application with raster graphics editor capabilities designed by ERDAS for geospatial applications. The latest version is 2010, version 10.1. ERDAS IMAGINE is aimed primarily at geospatial raster data processing and allows the user to prepare, display and enhance...
- Liquid Crystal Tunable FilterLiquid crystal tunable filterLiquid crystal tunable filters are solid-state optical filters that use electronically controlled liquid crystal elements to transmit a selectable wavelength of light and exclude others...