What is water-leaving reflectance?
Rrs is the ratio between water-leaving radiance (Lw, above the sea surface) and downwelling irradiance (Ed, above the sea surface). Lw can be estimated from above-water radiometric measurements, in this case reflected skylight must be removed using a “surface reflectance factor” (rho).
What is normalized water-leaving radiance?
The normalized water-leaving radiance is used in other algorithms to derive nearly all of the MODIS ocean products, e.g, the chlorophyll concentration. As such, it plays a central role in the application of MODIS imagery to the oceans.
What are reflectance values remote sensing?
Reflectance is the ratio of reflected energy to that incident on a body. The wavelength reflected (not absorbed) determines the color of an object. Scattered – The direction of energy propagation is randomly changed. Rayleigh and Mie scatter are the two most important types of scatter in the atmosphere.
What is surface reflectance?
Surface reflectance is the amount of light reflected by the surface of the Earth. It is a ratio of surface radiance to surface irradiance, and as such is unitless, with values between 0 and 1.
What is the difference between radiance and reflectance?
“Basically, you can think of radiance as how much light the instrument ‘sees’ from the object being observed. Reflectance is the ratio of the amount of light leaving a target to the amount of light striking the target. It has no units.”
How do you calculate surface reflectance?
Reflectivity can be calculated as p(y) = Gr(y)/Gi(y) where p is the reflectivity, y is the wavelength of the light, Gr is the reflected radiation and Gi is the incident radiation. Calculate reflectance from the reflectivity. Reflectance is the square of the reflectivity so q(y) = (Gr(y)/Gi(y))^2.
Does water have high or low reflectance?
Water Resources Systems Planning and Management 3.5. In the visible region of the spectrum (0.4 – 0.7 μm), the transmittance of water is significant and the absorptance and reflectance are low; the reflectance scarcely rises above 5%.
Why are there differences between the clear water and turbid water reflectance?
The turbid water reflectance spectrum exhibits higher values than clear water in the near-infrared region and approaches zero at longer wavelengths [44] . This is due to the concentration of solutes, sediments and organic matter, whose presence reinforces the reflection in the near-infrared band. …
How is reflectance measured?
Reflectance is measured by shining light on a sample and measuring the light reflected from the sample. Reflected light consists of specular reflected light and diffuse reflected light, which when combined together is referred to as total reflected light (specular reflected light plus diffuse reflected light).
Why is surface reflectance important?
Surface reflectance (SR) improves comparison between multiple images over the same region by accounting for atmospheric effects such as aerosol scattering and thin clouds, which can help in the detection and characterization of Earth surface change.