Spaceborne LS (e.g. Geoscience Laser Altimeter System - GLAS) provides global measurements of the Earth's surface with the potential on capturing additionally clouds and atmospheric aerosols. The spaceborne measurements allow to globally observe ice sheet and land elevations, approximate sea ice thickness, changes in elevation through time, vegetation coverage for biomass estimation, and height profiles of clouds and aerosols. It is a large footprint profiling system developed by NASA that operates with a footprint diameter of 70 m and measures elevation changes with decimeter accuracy. The surface characteristics are determined by comparing a parametric description of the transmitted and received waveforms. Because the laser footprint is large and illuminates multiple surfaces, the resulting return waveform is an integrated, spatially non explicit representation of the range to illuminated surfaces separated both vertically and horizontally. The geometric organization of surfaces within a single footprint can therefore not be determined.