Abstract
Surface estimation program BS-Horizon developed by Nonogaki et al. (2008) has the capability to save the estimated cubic B-Spline surface not only as a DEM but also as a cubic B-Spline function. The purpose of this study is to apply the surface in a form of cubic B-Spline function produced by BS-Horizon into the analysis in the fields of geomorphology and geology, and to develop a new analysis technique that is distinct from the one based on DEM.
As an example of practical use of the surface derived from BS-Horizon, we developed a new algorithm to exactly estimate some geomorphological characteristics, which are estimated by approximate calculation in the case of DEM, based on a set of coefficients of the cubic B-Spline function defined by BS-Horizon, and coded it in a FORTRAN program APP4OPT. Through the calculation of geomorphological characteristics using a mathematical function model, it was confirmed that APP4OPT estimates the target values exactly. Through the calculation using topographic map, it was confirmed that the new algorithm is available in the case of real topography. Furthermore, through the comparison between the results of analysis based on DEM and the ones based on the cubic B-Spline surface derived from BS-Horizon, it was proved that the present algorithm realizes the exact and continuous analysis using first derivative, second derivative and definite integration of the surface, which was never possible in the case of DEM.
