Comparison of a time domain spectral collocation method and the time-evolution backscatter model BORIS

Abstract

A model based on the time-domain spectral collocation method has been implemented at Forsvarets

Forskningsinstitutt (NDRE). The model can predict the time-series response from a sea floor defined

by two twodimensional matrices of compressional sound speed and density. At SACLANTCEN a model named BORIS (Bottom Response from Inhomogeneities and Surface) based on the timeevolution approach has recently been developed. Both models are briefly described, and the

implication of the different assumptions and limitations in both models are discussed. Five test-cases

have been defined in order to study and compare the responses. The test-cases range from a flat, homogeneous bottom to a bottom containing both roughness and volume Inhomogeneities. The comparisons show that the two models give similar results both from the surface and from the volume

inhomogeneities. The absolute levels of the signals from the spectral collocation model are generally

slightly higher than the levels from the BORIS model. This is believed to be due to the twodimensional

limitations in the spectral model.