What is "hyperspectral" imagery?
Hyperspectral imagery is in essence a picture that contains both spatially and spectrally continuous data. The term "hyper" means more than enough. If you have a "hyperspectral" image, you'll have more than enough spectra, or spectral bands, than you absolutely need to resolve whatever component you are looking for within the image. There is no agreed upon number of spectra that constitutes hyperspectral versus multispectral imagery. Typically, multispectral imagery consists of a handful of spectra, perhaps a dozen or fewer. Hyperspectral imagery often times consists of hundreds of spectra. For example, ITD's current hyperspectral imaging system can capture up to 1040 spectra.
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What are spectra?
Spectra are measurements of reflected energy. All objects reflect a certain amount of electromagnetic energy. The intensity of this reflected energy can be measured at various wavelengths. Many objects and substances have spectral characteristics that are unique. A unique spectral "signature" allows that object or substance to be identified through various spectral analyses.
Why do I need "more than enough" spectra?
In many cases, the whole is greater than the sum of the parts. With hyperspectral imagery, reflected energy is measured in very precise wavelengths and at very small increments. In this way, subtle spectral features associated with various objects and substances are recorded that might go unnoticed in broad band multispectral imagery.
What exactly is reflected energy?
When we speak of reflected energy, we are referring to all energy traveling in a harmonic wave pattern at the speed of light. Examples of this would include light generated by the sun, the lights in your home, or the fire in your fireplace. As this light travels from its source, it comes in contact with various objects, which absorb, transmit, and reflect that light in various proportions at various wavelengths. This is the same effect that causes the color that your eyes perceive. For example, the human eye can see light with frequencies ranging from about 400 to 700 nanometers, or blue, green and red light. A leaf on a tree reflects more green light (around 550 nanometers) than blue or red, which it absorbs for photosynthesis, and thus appears green to the human eye.
What is the spectral range of ITD's hyperspectral imaging systems?
ITD currently has three diffent types of sensors, each recording energy from different regions of the light spectrum. They are the
UltraViolet (UV) sensor, the Visible Near-InfraRed (VNIR) sensor, and the Short Wave InfraRed (SWIR) sensor. Together they record
reflected energy from 200 - 1700 nanometers.
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