Marine Remote Sensing - Technical Flashcards
Discuss the main differences in radiative transfer phenomenon in water vs on land - 5 things
- contribution of specular, sunglint reflections off the water surface
- changes in the surface roughness
- scattering across multiple depths
- scattering by molecules in the water
- reflections off the sea floor
Explain why radiometric resolution is of higher importance in marine applications compared to terrestrial ones
The fact that water is so dark puts a premium on the radiometric resolution of our satellite sensors (radiometric resolution is how many different levels of brightness we can reliably distinguish)
Define sunglint and explain how it alters our satellite observations
- what it is: brightening caused by reflections preferentially going in
the direction of the sensor (sun-sensor geometry) - how it alters observations: variation of surface reflection
depending on the shape of the water surface and the sun-sensor
geometry
Explain why atmospheric correction is especially critical in marine RS applications
because of the highly compressed range of radiation values from water
sunlight reflecting off the surface of waves
may cause misinterpretation of what we think we are seeing in RS images
most important and noticeable thing about passive remote sensing of water bodies is how dark the water appears
because the rate of radiation absorption is much higher in water
2 things about wavelengths and absorption
1) radiation is absorbed more and more as we go deeper in the water (penetration is decreased across all wavelengths)
2) water absorption is strongly wavelength dependent
a much smaller palette of wavelengths with which to work than on land
- no photons longer than the visible left to be scattered out of the water
- the magnitudes of the signal itself is quite low
The main thing to remember is that we’ll have a varying amount of surface reflection depending on the shape of the water surface and the sun-sensor geometry
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