Combining airborne and terrestrial laser scanning to monitor coastal processes

This study explores the potential of joint use of terrestrial (TLS) and airborne laser scanning (ALS) to quantify rapid and spatially inhomogeneous changes to the subaerial beach and to characterize the intensity of coastal processes. This remote sensing technology that uses scanning laser pulses for acquiring high-resolution three-dimensional surface of the measured object is applied to beach segment of the Pirita Beach (Tallinn Bay, the Baltic Sea). The extent and distribution of erosion and accumulation spots are analyzed by means of creating and comparing two digital terrain models of these areas from scanning point clouds obtained in different seasons. After elimination of systematic errors the ALS/TLS combination yields sub-decimeter accuracy for height determination of the beach. The analysis reveals not only the corresponding volume changes in the study area but also several features of internal dynamics of the beach across and along the waterline that are overlooked by classical monitoring methods. The benefits and shortcomings of combining the two laser scanning methods for monitoring coastal processes and the accuracy of the results are also discussed.