Satellite-based Information System on Coastal Areas and Lakes

Overview

SISCAL (Satellite-based Information System on Coastal Areas and Lakes) is an Internet-based service for the on-demand generation and distribution of Earth observation (EO) data products on aquatic ecosystems. SISCAL has been created in the frame of a three-year R&D project funded by the European Commission (EC) and is now operated by two members of the former SISCAL consortium: Informus GmbH, Berlin and Israel Oceanographic and Limnological Research Ltd., Haifa.

In its current operational state, SISCAL provides maps on parameters such as: Sea Surface Temperature (SST), Chlorophyll-a concentration, Total Suspended Matter (TSM)  and  Secchi depth, obtained from operational ocean observing instruments such as MODIS, MERIS or AVHRR. Through direct access to satellite data providers, products are available for most areas of the world either in near-real-time (defined here as 6-48 h after the satellite overpass) or from archived data.

SISCAL products can be integrated by the end user through a sophisticated, user friendly, off the shelf GIS system (SISCAL End-User GIS) that was modified to give automatic archiving functionality and practical analysis functions.

The main advantages of SISCAL are:

Ø      EO products from multiple sensors through one single entry point (data warehouse),

Ø      On-demand product generation for user-defined regions of interest and geographic coordinate systems,

Ø      Sophisticated GIS and archiving functionality through the SISCAL End-User GIS,

Ø      Flexible integration of local algorithms into the SISCAL processing chains.

Algorithms

The strategy for product generation in SISCAL is to use widely accepted state-of-the-art algorithms to derive bio-geophysical data products from Earth Observation (EO) data. These algorithms exist for the sea surface temperature and, to a lesser degree, for the retrieval of chlorophyll in clear open ocean waters. In contrast to that, remote sensing of water constituents in coastal areas or inland waters still needs to be considered as experimental (although it might be the only available source of information in remote areas).

Detailed description on the methods that SISCAL derive from ocean colour data, based on the spectral marine reflectance, the chlorophyll-a concentration, the total suspended matter concentration, the diffuse attenuation coefficient, the Secchi depth can be downloaded under http://www.siscal.net:8080/siscal/pages/downloads/SIS-ATB-005.pdf

Local Algorithms

The SISCAL service offers the possibility to integrate user-provided algorithms into the operational processing chain. This allows the implementation of algorithms into SISCAL that have been developed for particular environmental conditions where they are more successful than the globally applicable standard algorithms.

User-provided algorithms can be kept private or made available to subgroups or all registered SISCAL users. SISCAL is therefore an ideal tool for both operationally deriving locally optimised products or for testing newly developed evaluation methods.

GIS functionality

For comfortable archiving of SISCAL data products as well for visualisation and advanced analysis, a GIS tool based on the ArcView 8.x software and the Spatial Analyst extension from ESRI has been developed by IOLR Ltd. Haifa, Israel. End users that do not dispose of their own specifically tailored GIS system will advantageously use the SISCAL GIS for a number of purposes:

Ø      The EU-GIS enables the end-user to automatically archive EO products and the corresponding metadata downloaded from the SISCAL server;

Ø      During the archiving process, the tool analyses the incoming data products and provides statistics in order to alert users about significant anomalies of parameters of interest occurring in their area of interest;

Ø      A variety of advanced raster based GIS functions were developed that can be applied to a specified region of interest. These include: Calculating averages of EO products; Differencing of EO products for locating extreme variations; Creation of short term and long term trend graphs; Segmentation of EO products according to defined thresholds for locating suspicious areas; Creation of daily statistical reports for user-defined regions of interest, e.g. near outlets along the coastline; Creating line profiles for any EO product at any specified date; Animating the variations in physical values for visual inspection and demonstration of these variations in simple manner to decision makers and the creation of special composites based on near-real-time EO products and known historical behaviour of the ecosystem (for instance creation of water quality index based on CHL and SST products). Detailed description of the EU-GIS functions can be downloaded under http://www.siscal.net:8080/siscal/pages/downloads/eu-gis-handbook.pdf.

Innovative aspects of SISCAL