A quick one minute answer – ...

A quick one minute answer – let me know if it is as clear as mud. Remote sensing is usually referring to satellite sensor collection of reflected sun light from the earth surface. Reflected light is captured in numerous band, colour bands, infra-red bands etc. Spectral reflection is the intensity number of the ‘light’ band captured in the various bands (spectrum). There are various methods developed that use ratios between bands to identify vegetation and soil types etc. Water usually comes out black i.e. absorbs all light, but if has high sediment load, algae, water plants, shallow depth (might get reflectance from underlying stream sediments) different reflectance values are obtained. With satellites covering the same area every few days one can do change detection on a water body. Amount of moisture in vegetation can be picked up – that’s a little more complicated.