Grid Development 3.1. Grid Interpolation [15] The ANUDEM software [Hutchinson, 1988, 1989] was used for creation of the grid. The interpolation algo-
rithm implemented by ANUDEM uses an iterative finite difference technique that combines the surface continuity of global interpolation methods (i.e., splines or kriging) with the computational efficiency of local interpolation methods [Hutchinson, 1989]. ANUDEM obtains realistic drainage structures through two different processes: (1) the use of a roughness penalty and (2) the option of a drainage enforce- ment algorithm. The roughness penalty is introduced into the algorithm to provide a mechanism to assign relative weightings to first derivatives (slope) and second derivatives (curvature), and thus determine the nature of the interpolat- ing function. A minimum-curvature surface is created when the roughness penalty approaches 0 (indicating a heavily weighted second derivative), and a minimum potential surface is created when a roughness penalty approaches 1 (indicating a heavily weighted first derivative). A rough- ness penalty of 0.5 was used for the interpolation of the Gulf of Papua grid. Hutchinson [1988] recommends that a roughness penalty of 0.5 be used when gridding data sets containing randomly spaced points. The adjustable rough- ness penalty used in ANUDEM is similar to the use of a tension parameter [Smith and Wessel, 1990] in minimum curvature splines. Both techniques provide a compromise between minimum curvature and minimum potential sur- faces to maintain artifact-free behavior of the interpolated surface in areas with few, widely spaced data points. [16] The drainage enforcement algorithm of ANUDEM is typically used to create hydrologically sound digital eleva- tion models in areas of sparse data coverage (specifically in the subaerial environment). The suitability of such an algorithm to the marine environment is not well docu- mented though Harris et al. [2005] and Crockett et al. [2008] describe continental shelf valleys in the Gulf of Papua and eastern Torres Strait characterized by closed bathymetric contours. These features suggest that the Gulf of Papua shelf is not a hydrologically sound surface and hence drainage enforcement was not appropriate. The effect of gridding the SRTM data set with a drainage enforcement algorithm is beyond the scope of this paper. Other gridding techniques such as kriging and triangular irregular networks were used to interpolate the grid. However, both methods took an excessive amount of time to complete and were abandoned. [17] The grid bounds were 6.0–14.0S 140.0–150.0E with a 3.600 cell size. The 3.600 cell size (110 m) was con- sidered sufficiently fine to resolve structures of interest
ตารางการพัฒนา 3.1 ซอฟต์แวร์ตาราง ANUDEM แทรกแทรง [15] [Hutchinson, 1988, 1989] ถูกใช้สำหรับการสร้างตาราง Algo แทรกแทรงการ-rithm implemented by ANUDEM uses an iterative finite difference technique that combines the surface continuity of global interpolation methods (i.e., splines or kriging) with the computational efficiency of local interpolation methods [Hutchinson, 1989]. ANUDEM obtains realistic drainage structures through two different processes: (1) the use of a roughness penalty and (2) the option of a drainage enforce- ment algorithm. The roughness penalty is introduced into the algorithm to provide a mechanism to assign relative weightings to first derivatives (slope) and second derivatives (curvature), and thus determine the nature of the interpolat- ing function. A minimum-curvature surface is created when the roughness penalty approaches 0 (indicating a heavily weighted second derivative), and a minimum potential surface is created when a roughness penalty approaches 1 (indicating a heavily weighted first derivative). A rough- ness penalty of 0.5 was used for the interpolation of the Gulf of Papua grid. Hutchinson [1988] recommends that a roughness penalty of 0.5 be used when gridding data sets containing randomly spaced points. The adjustable rough- ness penalty used in ANUDEM is similar to the use of a tension parameter [Smith and Wessel, 1990] in minimum curvature splines. Both techniques provide a compromise between minimum curvature and minimum potential sur- faces to maintain artifact-free behavior of the interpolated surface in areas with few, widely spaced data points. [16] The drainage enforcement algorithm of ANUDEM is typically used to create hydrologically sound digital eleva- tion models in areas of sparse data coverage (specifically in the subaerial environment). The suitability of such an algorithm to the marine environment is not well docu- mented though Harris et al. [2005] and Crockett et al. [2008] describe continental shelf valleys in the Gulf of Papua and eastern Torres Strait characterized by closed bathymetric contours. These features suggest that the Gulf of Papua shelf is not a hydrologically sound surface and hence drainage enforcement was not appropriate. The effect of gridding the SRTM data set with a drainage enforcement algorithm is beyond the scope of this paper. Other gridding techniques such as kriging and triangular irregular networks were used to interpolate the grid. However, both methods took an excessive amount of time to complete and were abandoned. [17] The grid bounds were 6.0–14.0S 140.0–150.0E with a 3.600 cell size. The 3.600 cell size (110 m) was con- sidered sufficiently fine to resolve structures of interest
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