Extracting Tree Heights over Topography with Multi-Spectral Spaceborne Waveform Lidar

It is generally agreed that the optimal footprint size for a spaceborne lidar is 30 m. Over topography such a large footprint can blur the canopy and ground signal together preventing information extraction. Multi-spectral lidar waveforms have been simulated with Monte-Carlo ray tracing over explicit geometric forest models. A method for using multi-spectral waveform lidar to distinguish ground from canopy returns has been tested over a range of ground slopes. The results are promising, with an initial error of +/-5 m for a signal level of only 5,000 photons with noise; an easily achievable figure. The inversion algorithms completely dominate inversion errors for all cases above 10,000 signal photons.