Spatio−temporal Analysis of Beach Morphology Using Lidar, Rtk− Gps and Open Source Grass Gis

Modern mapping technologies used for coastal studies such as LIDAR and RTK−GPS produce massive amounts of data characterized by oversampling and noise. The physical phenomena and landscape changes examined are often subtle and besides statistical accuracy, adequate representation of surface geometry is crucial for correct interpretation of measured data. We have explored the suitability of the Open source GRASS GIS and its spline based spatial interpolation for assessment of rapid changes in topography of nourished beach on Bald Head Island, NC based on the LIDAR 1997−2000 and RTK−GPS 2001−2002 data. Surface gradient and curvatures, needed for topographic analysis were computed simultaneously with interpolation. Raster map algebra was used for data management (masking, extraction of subsets) as well as for spatio−temporal analysis, such as computation of first and second order differences between surfaces and volumes of lost sand. Visualization of multiple 3d surfaces with moving cutting planes provided powerful tools for visual identification of features and beach morphology changes.