The sedimentary architecture and bedrock topography of alpine and peri-alpine valleys result principally from processes active in former glacial and peri-glacial environments. Along ancient margins of the glaciers, lateral and vertical changes of sedimentary facies are relatively abrupt, but in the centers of the valleys and basins the lithofacies are rather continuous. In applied and fundamental research related to glacial deposit geology, details at a variety of scales are required. Interpretations of gravity data constrained by geological and other geophysical information are generally most appropriate for resolving large-scale problems. Pugin's (1988) depth-to-bedrock map for the western Swiss Plateau was drawn on the basis of compilations of geological and geophysical data, including pseudo-2 D density models derived from the residual Bouguer gravity maps of Olivier (1983). At any one location the reliability of the isopach contours on Pugin's (1988) map depends mainly on the density and quality of the original gravity data, on the suitability of the regional-residual Bouguer anomaly separation,on the availability of relevant rock property information and on the presence or absence of compacted sediments older than the last glacial cycle. The revised depth-to-bedrock estimates for the Aubonne valley, based on new gravity measurements. Bouguer anomaly calculations, regional-residual separations and borehole information(Meyer de Stadelhofen. this issue), merely highlights the ambiguity of interpretations of gravity data noted by Pugin (1988).