Unit 8 Flashcards
How is hyperspectral remote sensing different from multispectral?
It has 100s of bands that range spectral resolutions. Can estimate the relative abundance of certain features not just their presence or absence.
What is the benefit of imaging spectroscopy
Can use the full spectrum for analysis giving higher resolutions
= determine vegetation health, water content, types of vegetation etc.
How does a spectral sample from imaging spectroscopy differ from multispectral such as landsat
Instead of inferring the spectral signature from about 5 bands per pixel we have contiguous spectral bands giving a more accurate view of the signature
Where does the best spectroscopy occur currently?
Airborne, but increasing interest in spaceborne
Why is imaging spectroscopy area-based?
Since it flies over numerous targets there is gridded data that allow for formation of images based on the spectral bands
What are examples of airborne imaging spectrometers?
AVIRIS, AVIRIS-NG, CASI/SASI
How can we use a library of vegetation spectra?
TO map vegetation types and conditions
What are examples of space borne imaging spectrometers?
Hyperion, Hyspiri, ENMAP
What is the challenge of imaging spectroscopy and being area-based?
Have to tease out individual objects from the mixed pixels (spectral mixing) through unmixing methods
What is linear spectral unmixing?
Using information to determine the fraction or percentage of each feature from known/expected spectral signatures that they have
What is an endmember?
A pixel that is assumed to have a pure spectral signature for a given land cover class (Ie. open water)
What is a common method of unmixing in land use/land cover studies?
Sub-pixel fractions: applied to optical multi-spectral imagery to derive fractions of specific land cover types
What radiation does thermal remote sensing use?
emitted longwave radiation from emitted the earth’s surface (terrestrial)
What are the major uses of thermal remote sensing?
To monitor surface temp changes (dirunal, seaonal, interannual) + the earth’s energy budget
the internal true temperature of an object from the molecular vibrations
Kinetic temperature
define radiant temperature
result of emitted energy from an object also called the apparent or brightness temperature
How does wein’s displacement law relate to thermal remote sensing?
All objects emit EM energy and the amount/wavelength is based on the temperature of the object. Hotter objects have smaller wavelengths (inverse relationship).
Therefore we can use this to distinguish features in thermal remote sensing
What is a blackbody?
A theoretical object that is a perfect emitter and absorbs all energy = does not reflect anything
What happens to emissivity if the radiant temperature is lower than the actual kinetic temperature of an object?
The emissivity will be low
What example increases the emissivity?
Water content
Are most thermal sensors imaging sensors?
Yes, in comparison LIDAR is not
What are some examples of thermal imaging sensor missions?
Landsat, MODIS, ASTER, GOES, ECOSTRESS
How can evaporation be used with thermal imaging?
Evaporation causes a slight decrease in temperature so we can infer water stress
