Lidar Waveform Correlation Images:  A New Method for Detecting Subtle Topographic Change

Michelle Hofton, J. Bryan Blair (GSFC), Scott Luthcke (GSFC)

Changes in the Earth’s topography reveal the processes at work within the Earth. Using space-based measuring deformation with millimeter accuracy on spatial scales of tens of meters to kilometers and time scales from minutes to years. As a result, our understanding of the mechanics of the earthquake cycle and of active deformation has been revolutionized in many plate boundary zones, on volcanoes, and in areas affected by land subsidence. A technique attracting increasing attention for its ability to make accurate, high-resolution topographic and topographic change measurements is laser altimetry, also referred to as lidar. This collaborative effort between UMD and Goddard further develops and demonstrates the accuracy and precision of vertical surface change measurements made by correlating images constructed from lidar return waveforms. This innovative approach to extracting surface deformation from lidar waveform information has the potential to detect change at the sub-centimeter level.

 

The research has two components: (1) the extension of existing simulations to include the recently-developed and enhanced lidar measurement model in order to achieve sub-centimeter-level precision of relative surface change measurements on all terrain types, and (2) the collection and differencing of temporally-distributed lidar waveform images to assess the precision and accuracy of surface change measurements over static and deforming sites. 

We use NASA’s LVIS airborne research instrument to collect data from two test sites, a “zero-change” site, and an area undergoing subsidence due to sub-surface coal mining. The zero-change site will be used to validate our simulations and establish the precision of lidar waveform measurements for measuring surface change on different land use, land cover, and terrain types. The area of active sub-surface mining provides a predictable, “engineered” surface with displacements similar in scale and magnitude to natural tectonic events.

Example publication: M. A. Hofton and J. B. Blair, Laser altimeter return pulse correlation: A method for detecting surface topographic change, Journal of Geodynamics, 34, 491-502, 2002.