Analysis of temperature maps of waterbodies obtained from ASTER TIR images

Abstract

Thermal water pollution is a highly relevant issue to which increasing attention is being paid. Satellite remote sensing represents a useful tool for the mointoring and study of the temperatures of waterbodies. The purpose of this work is to define a methodology for the analysis of the surface temperature maps of coastal waterbodies and watercourses from satellite images for quality assessment and for regulatory purposes. Three different procedures are developed in order to study the temperature field of waterbodies, to extract the temperature profile at a fixed distance from the coastline and to analyse the cross sections of the watercourses as prescribed by the law. Extraction and analysis of surface temperature patterns are undertaken using image segmentation techniques. This work also represents a first test of the advantages given by the Sharpening Water Thermal Imagery (SWTI) algorithm, which improves the spatial resolution of Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) images from 90 to 30 m. The developed procedures and the SWTI algorithm are applied to ASTER images acquired on the lagoon of Venice and on the delta of the Po River. Statistical parameters and temperature profile are extracted in order to verify compliance with legal limits. The use of the developed procedures enables the individuation and quantification of thermal anomalies such as industrial discharges both in the sea and in watercourses.

Acknowledgements

The authors thank the Ministero delle Infrastrutture e dei Trasporti – Venice Water Authority – through its dealer, Consorzio Venezia Nuova, for provision of data. The authors are grateful to the anonymous referees who suggested valuable improvements to this paper.