Quantitative Estimation of Variability in the Underwater Radiance Distribution (RADCAM)
Abstract
A significant source of uncertainty in the prediction of the apparent optical properties of the ocean is the geometrical distribution of the radiance field and its variation with respect to time and space; this uncertainty directly affects attempts to use measurements of reflectance and attenuation for the diagnosis of ocean constituents. Uncertainties in the time and depth dependent variations in the radiance distribution, and their sources of variation, propagate as well to the prediction of the performance of new imaging systems such as the ?virtual periscope?. The problem starts at the sea surface, where the generally unknown sky radiance distribution, coupled with a roughened air-sea interface, plays a major role in the transmission of sun and sky radiance to below the surface. In the ocean interior, the volume scattering function, and the absorption coefficient alter the radiance distribution in both the forward and backward direction; in the perhaps usual situation of multiple scattering, the uncertainty in the radiance distribution becomes large. In optically shallow areas, non- Lambertian bottom reflectances add to the uncertainty. Our long-term goal is to develop and deploy a relatively simple means for the measurement of the full radiance distribution, which could be routinely deployed by the optical oceanographic community. A further side benefit would be that many of the measurements currently made, such as planar and scalar irradiance, angle-dependent Q factor etc., could be made by various integration operations on the measured radiance field rather than with mechanical diffusers. The potential interferences of various deployment platforms (e.g. shading, reflectances by ships, buoys and towers) could be measured directly rather than inferred based on inaccurate assumptions about the underwater radiance distribution. A direct confirmation of the asymptotic radiance distribution can be made.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2009
- Accession Number
- ADA527142
Entities
People
- Marlon R. Lewis
- Ronnie V. Dommelen