Water turbidity estimation using a hand-held spectropolarimeter to determine surface reflection polarization in visible, near and short-wave infrared bands
This letter describes a radiometric technique to evaluate the turbidity (suspended solids concentration, SSC) of terrestrial waters (e.g. irrigation canals, creeks, ponds, streams and small rivers) using a hand-held spectropolarimeter. A field experiment was conducted using a container of water with different turbidity levels. The intensity and degree of polarization of sunlight reflected from the water were measured in visible, near and short-wave infrared bands. The intensity of the reflected light and its non-polarized component were divided by the incident sunlight intensity to derive the radiant coefficient (Q, %), and the non-polarized radiant coefficient (Qnp, %), respectively. The Q and Qnp in several wavelength bands were regressed against measured values of SSC. The multiple regression model using multi-band Qnp is superior to a similar model using multi-band Q because the Qnp model does not need viewing angles as explanatory variables, whereas the model using Q requires these angles. A result from preliminary testing in real streams is also presented.
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Document Type: Research Article
Affiliations: National Institute for Agro-Environmental Sciences, Tsukuba, Ibaraki 305-8604, Japan
Publication date: 2007-01-01