File name: Readme_FUB-WeW-Water_Beam.txt Authors: Thomas Schroeder and Michael Schaale Affiliation: Institute for Space Sciences Freie Universitaet Berlin Department of Earth Sciences Carl-Heinrich-Becker-Weg 6-10 D-12165 Berlin, Germany E-mails: Thomas.Schroeder@wew.fu-berlin.de Michael.Schaale@wew.fu-berlin.de Document title: Brief Documentation of the FUB/WeW WATER Processor A plug-in for MERIS/(A)ATSR Toolbox (BEAM) Release date: 23 March 2005 Introduction ------------ This file briefly describes the installation and use of the accompanying software package. This Plugin makes use of MERIS Level-1b TOA radiances in the bands 1-7, 9-10 and 12-14 to retrieve the following case II water properties and atmospheric properties above case II waters : - chlorophyll-a concentration (log scale, mg/m^3) - yellow substance absorption @ 443 nm (log scale, 1/m) - total suspended matter concentration (log scale, g/m^3) - aerosol optical depth @ 440 nm - aerosol optical depth @ 550 nm - aerosol optical depth @ 670 nm - aerosol optical depth @ 870 nm - water-leaving RS reflectance @ 412 nm (1/sr) - water-leaving RS reflectance @ 442 nm (1/sr) - water-leaving RS reflectance @ 490 nm (1/sr) - water-leaving RS reflectance @ 510 nm (1/sr) - water-leaving RS reflectance @ 560 nm (1/sr) - water-leaving RS reflectance @ 620 nm (1/sr) - water-leaving RS reflectance @ 665 nm (1/sr) - water-leaving RS reflectance @ 708 nm (1/sr) The retrieval is based on four separate artificial neural networks which were trained on the basis of the results of extensive radiative transfer simulations with the MOMO code by taking varying atmospheric and oceanic conditions into account. All networks were validated against in-situ measurements. During the Plugin processing the MERIS Level-1b data are masked prior to the retrival by applying the following combination mask : GLINT_RISK | LAND_OCEAN | BRIGHT | COASTLINE | INVALID The masked pixel's values are set to +5.0. Non-masked pixels are then normalized for an atmosphere's ozone contents of 344 Dobson units by calculating transmission correction factors. Notice that the AOT wavelengths 440, 670 and 870 nm correspond to the AERONET data wavelengths for a convenient direct comparison with in situ data. Each pixel is checked against the input and output values margin of the trained networks. Additional flags are set in case of a neural network failure for input and output separately. The radiative transfer simulation code and the retrieval algorithm are described in detail in the papers cited in the references section below. We would like to stress the fact that this plugin is applicable over case II only, thus it is likely to fail over the open ocean by producing negative remote sensing (RS) water-leaving reflectances. Requirements ------------ The FUB/WeW WATER processor is a plug-in module for the BEAM software developed by Brockmann Consult for ESA. This latter software must of course be installed prior to the FUB/WeW WATER processor. The BEAM software includes an application programming interface (API) and a set of executable tools to facilitate the use of MERIS, AATSR and further ASAR data products of the ESA ENVISAT satellite. It can be freely downloaded from: http://scipc3.scicon.gkss.de/services/beam2/software/ Installation ------------ The BEAM package (here : BEAM VISAT Version 3.2) is installed within a particular, user-selectable, directory. For the purpose of this documentation file, that directory will be denoted $BEAM_HOME$. After installation of the BEAM package, this directory should contain the following subdirectories and files: $BEAM_HOME$ |- auxdata/ |- bin/ |- docs/ |- extensions/ |- jre/ |- lib/ |- license/ |- log/ |- api-doc.zip |- changelog.txt |- epr_api-2.0.5.zip |- examples.zip |- known-issues.txt |- readme.txt |- src.zip |- version.txt The FUB/WeW WATER processor plug-in, named 'wew_water.jar', must simply be added to the $BEAM_HOME$/extensions/ and $BEAM_HOME$/lib/ subdirectories. The BEAM application (VISAT) will automatically integrate the FUB/WeW WATER processor within its interface. Operation --------- Once the BEAM software and the FUB/WeW WATER processor have been installed, the package can be operated in two different modes: interactive and automatic. To launch an interactive session, start the main BEAM software application (VISAT) and select the FUB/WeW WATER processor using the following menu selections: Tools -> FUB/WeW WATER Processor. A dialog window will appear: - Select the input file containing the MERIS Level-1b data to be processed. - Specify the output file where you want the results to be written. - Select the output format from the pull-down menu, if different from the BEAM default. - Optionally, save this configuration in a separate XML file, known to BEAM software as a (reusable) 'processing request'. - Initiate the FUB/WeW WATER processor itself by clicking on the 'Run' button. To process one or more data sets automatically, i.e., without requiring manual input, it is also possible to launch the application from the command line (or an executable script, for that matter). For convenience we supplied the (UNIX) script WaterProcessor.sh to run the FUB/WeW WATER processor in its interactive or non-interactive (= batch) mode. First the variable BEAM_HOME in WaterProcessor.sh must be adapted and InputProduct and OutputProduct in WaterProcessor.xml must be adapted, too. Then this script may be launched from anywhere in the following modes : Interactive mode : WaterProcessor.sh -i Interactive mode with debug info : WaterProcessor.sh -i -d Interactive mode with predefined request : WaterProcessor.sh -i WaterProcessor.xml Batch mode with predefined request : WaterProcessor.sh WaterProcessor.xml Warranties and copyright information ------------------------------------ The FUB/WeW WATER processor package described in this document is provided 'as is', with no warranty of merchantability or fitness to any particular purpose. Although every effort has been made to ensure accuracy of computations and conformity to the algorithms as published in the references below, the authors assume no responsibility whatsoever for any direct, indirect or consequential damage resulting from the use of this software. The FUB/WeW WATER processor is distributed free of charge and cannot be sold or re-sold. It can be copied and distributed further, provided all documentation is attached and provided the original source of the software is explicitly and prominently described. Questions, concerns and problems should be referred to the authors of the software package at the address indicated at the start of this file. The copyright on this file and the associated software remains with the Institute for Space Sciences (WeW), Freie Universitaet Berlin. References ---------- Fischer J., and Grassl H., "Radiative transfer in an atmosphere-ocean system: an azimuthally dependent matrixoperator approach", Applied Optics, 23, 1032-1039, 1984. Fell F., and Fischer J., "Numerical simulation of the light field in the atmosphere-ocean system using the matrixoperator method", Journal of Quantitative Spectroscopy & Radiative Transfer, 69, 351-388, 2001. Schroeder Th., Schaale M., Fell F. and Fischer J., "Atmospheric correction algorithm for MERIS data: A neural network approach", In: Proceedings of the Ocean Optics XVI Conference, Santa Fe, New Mexico, USA, published on CD ROM, 2002. Schroeder Th., Fischer J., Schaale M. and Fell F., "Artificial neural network based atmospheric correction algorithm: Application to MERIS data", In: P roceedings of the International Society for Optical Engineering (SPIE), Vol. 4892, Hangzhou, China, 2002. Schroeder Th., and Fischer J., "Atmospheric correction of MERIS imagery above case-2 waters", In: Proceedings of the 2003 MERIS User Workshop, ESA ESRIN, Frascati, Italy, 2003. Schroeder, Th., "Fernerkundung von Wasserinhaltsstoffen in Kuestengeweassern mit MERIS unter Anwendung expliziter und impliziter Atmosphaerenkorrektur- verfahren", Ph.D. Dissertation, Freie Universitatet Berlin, Berlin (Germany), 2005, http:/www.diss.fu-berlin.de/2005/78