Coastal Management
The scanner was mounted on an elevating tripod 4 m above the ground. The average space between nearby scan positions was about 300 m. Seven to eleven individual scans were conducted each day (10:00AM-4:00PM) and 50 scans. According to the water level measurements archived by National Oceanic and Atmospheric Administration (NOAA, https://tidesandcurrents.noaa.gov), the daily high tide and low tide occurred at 8:00-9:00AM and middle night at Freeport, TX, respectively. The tidal height is about 0.6 m at this site. Accordingly, the water level during our surveying time (10:00AM-4:00PM) was slightly higher than the daily average water level.The difference between the Mean High Water (MHW) and the Mean Low Water (MLW) at this site is about 0.4 m.
Data Collection:
time: may of 2015 and 2016
instruments: Riegl VZ-2000 LiDAR scanner, tripods, reflectors, r10GPS.
Fig.1 Field survey photos and visualization of raw data
Generating DEMs
Fig.2 Coordinate rotation sketch and matrix
Fig.3 The 2D_hill_shaded topographic map
Fig.4 Cross-dune profile derived from DEM (X=4500m)
The process of rotation plays the roles like Priciple Components Analysis (PCA). The beach and dune area occupies a smaller portion of the entire area. A larger area produces more grid cells, which require larger data storage, longer computation time, and result in a larger output file. In order to minimize the size of the study area, the UTM coordinates of these octree-terrain-filtered points were rotated by 40 degrees in the anticlockwise direction
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Fig.5 The result of quality check