sentence1: crandall et al detect the ice-air and ice-bed layers in individual radar echograms by combining a pre-trained template model and a smoothness prior in a probabilistic graphical model .
sentence2: specific case of ice , crandall et al detect the ice-air and ice-bottom layers in echograms along the flight path by combining a pretrained template model for the vertical profile of each layer and a smoothness prior in a probabilistic graphical model .