Airborne laser scanner survey around the APLIS07 icecamp
H. Skourup and R. Forsberg, Danish National Space Center, email@example.com, firstname.lastname@example.org In connection with DAMOCLES field work 2007 the Danish National Space Center (DNSC) contributed with an extensive airborne survey in the area around APLIS07 icecamp on April 12, 2007. The main task was to collect high resolution laser scanner data in order to estimate the sea ice freeboard. The DNSC laser scanner system provides ice height data at a resolution of approx. 1 m in a 250 m wide swath. The flight tracks were chosen to be coincident to other ongoing sea ice activities in order to compare the results, giving deeper insight into various measurement methods and sea ice processes.
In Figure 1 (left) all the flight tracks are mapped. An approximate 100 km long track was flown parallel to an ICESat track, and an approximate 70 km long line was flown coincident to earlier flown AWI helicopter borne EM-bird thickness measurements. The GPS icedrift information available at the flight epoch was used for waypoint definition. The small red inner box is shown in details in upper right corner of Fig. 1. It shows the flight tracks of a detailed mow-the-lawn pattern to survey the icefloe at which the icecamp was located and the adjacent runway area. An area of approx. 5 x 2 km was covered, centerede on the APLIS camp. The spacing between the lines were narrower than the width of the laser scanner, and thus the entire area should be fully covered.
Finally the large red outer box, shown in details in the lower right figure, maps the survey pattern corresponding to track lines (1-6) surveyed by a British nuclear submarine, which maps the sea ice from below by upward looking sonar (ULS). The return flight line no. 7 represents a survey line measured by EM.
The laser scanner data from the survey has not yet been processed. The final product will be delivered as freeboard maps with a horizontal resolution ~1x1m. For an example see Figure 2. The width of the laser scanner is approximately the same as the flight altitude (~250 m), and the vertical precision are primarily determined by the errors of the GPS solutions in the order of decimeters, due to the long baselines. There is in total 3 scanner files (each ~200 Mb) each representing 1hr of data, and also scanner data flying into camp from Inuvik, Canada, on April 12, and leaving for Sachs Harbour, Canada, on April 13.
The flight tracks extracted from the GPS-slaved onboard inertial navigation system (INS) are available. The files are:
102b_ice.coo EM and ICESat
Figure 2 An example of lidar swath (of width ~250 m) sea ice freeboards. Units in metres. he data files are in ASCII format with 4 columns, representing the time (UT) in decimal hours, latitude and longitude in decimal degrees (WGS84), and the flight altitude in metres.