Precise and Accurate High-Altitude Waveform Lidar Mapping of Greenland Land and Arctic Sea Ice in Support of Operation IceBridge

NASA's LVIS is an airborne, medium-footprint (25m diameter), full waveform-recording, airborne, scanning lidar system that has been used extensively for mapping surface structure for various scientific investigations. The system digitally records the shape of the returning laser echo, or waveform, after its interaction with the various reflecting surfaces of the earth, providing a true 3-dimensional record of the surface structure within each footprint in the data swath. In April 2009, the system was flown over regions of the Greenland ice sheet and Arctic Ocean on board NASA’s P3-B aircraft as part of NASA’s Operation IceBridge. Flying at ~8 km altitude, using ~25 m-wide laser footprints that were contiguous along and across-track within the ~1.5-wide laser swath, a total of ~9,800 lineal km of ICEsat repeat ground-track "corridors" over land and sea ice were imaged during three flights, including ~1,200 lineal km that were imaged previously using LVIS in September 2007. Data collected included ground elevation and vertical extent measurements for each laser footprint, as well as the vertical distribution of intercepted surfaces (the return waveform) from which surface slope, roughness and other metrics can be extracted. Data precision and accuracy are assessed, including as a function of surface conditions. Data along four long (>1,000 km) tracks of data are compared to cotemporal, coincident data collected by ICESat in order to establish the accuracy of the sensor-to-sensor comparison under various surface conditions. These data, along with data collected by the other sensors involved in Operation IceBridge, form the basis for future repeat surveys of the ice sheet and its margins from the air during the data gap between the current orbital ICESat and future lidar missions. In particular, the data set collected using the LVIS sensor will provide a consistent datum to enable inter-mission calibration and validation as well as the separation of inter-mission observational system biases and errors from true decadal and seasonal surface elevation change.