INTRODUCTION

HOPAS is a new, powerful and proven system to analyze and monitor water quality and composition, accepting inputs from remote sensors and satellite imagery.

The Hydro-Optical Analysis System (HOPAS) combines an advanced radiative transfer model with a powerful nonlinear programming algorithm to enable easily obtained optical water measurements to be transformed into information on the composition and concentration of materials that effect water quality. For the first time, measurements of the light field from satellites, aircraft, moorings and ships can be rapidly inverted to obtain accurate estimates of phytoplankton, suspended mineral particles, and dissolved materials. At the same time, HOPAS provides a true information system that has unparalleled capabilities to merge diverse types of data with the optical calculations and to view this information within a dynamic spatial and temporal context. HOPAS will enable scientists, environmental engineers, and aquatic resource managers to use easily obtained in situ or remotely sensed optical data to understand and manage aquatic ecosystems. HOPAS will alleviate the need for expensive, labor-intensive laboratory analysis of water samples for use in addressing water quality issues, including microbial growth in drinking water supplies, surface pollutants from farms, industries, vessels, and domestic sources, algal blooms, fisheries and mariculture, and protection of coral reefs and sea grass beds.

TECHNICAL OUTLINE

Understanding, monitoring, and managing aquatic ecosystems requires information such chlorophyll, CDOM, and mineral concentrations, absorption and scattering coefficients, and bathymetry and bottom classification in shallow waters. Such data are difficult and expensive to obtain with high spatial and temporal frequencies. On the other hand, remotely sensed in-water optical data (e.g., reflectances, irradiances, upwelled radiances) are routinely obtained from aircraft, satellites, moorings, and profiling instruments. Extracting the desired aquatic environmental information from these optical measurements is, however, a difficult radiative transfer inverse problem.

We have developed a new implicit inversion algorithm for extracting aquatic environmental information from the optical data. Our method employs an iterative inversion of the optical data using extract numerical solutions of the radiative transfer equation (RE, obtained from EcoLight, a special version of HydroLight, see www.hydrolight.info) and a Generalized Reduced Gradient non-linear search algorithm.

HOPAS uses EASy to read in and display the results of our newly developed radiative transfer inversion algorithm and associated software. HOPAS uses EASy to read in and display optical data, select optical data for inversion, and display the results obtained from the data inversion. The data inversion software includes a graphical interface (which runs within EASy) that allows the user to specify the environmental information to be obtained from the inversion, formulate constraints, enter initial guesses, and define the desired inversion.