Characterisation of coastal and inland waters with space sensors

The objective is to document the present capabilities of Earth Observation (EO) for quantitative estimate of geophysical parameters related to inland and coastal “water quality”. Further, to investigate the improvements that can be expected with the new generation of EO sensors, and to give a prospective view of what could be achieved in the longer term with optimized satellite instruments. The project has involved a review of user requirements, an extensive literature review concerning space remote sensing techniques and algorithms, an explicit comparison of the EO capability with the identified-application requirements. A customer segment investigation shows that there are many different user-groups who can benefit from using information from a few key satellites, e.g., SPOT, Landsat, NOAA, and ocean color sensors to some extent. The main finding is that there is a limited number of specific requirements to the quantitative measurements that EO data can presently provide. It appears that EO data can contribute with information within many applications, but use of EO data to extract useful parameters can only be done for about 15 to 20 parameters relevant for observation of “water quality”. From a technical point of view, most of the algorithms making use of EO data are based on empirical models that are not directly applicable to coastal and inland waters in general. Moreover, these types of algorithms are hardly applicable to regions with lack of in situ data. Hence it is difficult to predict the accuracy that could be achieved in specific regions. Most applications that relate to inland and coastal waters require spatial resolution of about 100 m or better. This accuracy is not met with present sensors, since they are not dedicated to operational issues and local investigations. However remote sensing has already a valuable and recognized role in defining baseline conditions. For example the impact of natural disasters can be evaluated against these conditions, even if remote sensing cannot play a very helpful operational (real-time) role during the evolution of a disaster. During the next decade, several sensors will be launched, which should partly overcome the current limitations of EO sensors. Hyperspectral sensors, very high resolution instruments, multi-satellite constellation and application-dedicated micro-satellites are foreseen to improve drastically the capability of remote sensing for serving operational monitoring of inland and coastal waters. Associated with these new technologies, improved algorithms and new methods are being developed. Their potentials for operational uses remain to be documented and demonstrated.NERSC Technical Report no. 164. Funded by European union, Contract no. 14049-1998-06 F1ED ISP N