Horizontal accuracy assessment of a novel algorithm for approximate a surface to a DEM

Abstract. This study evaluates the horizontal positional accuracy of a new algorithm that defines a surface that approximates DEM data by means of a spline function. This algorithm allows evaluating the surface at any point in its definition domain and allows analytically estimating other parameters of interest, such as slopes, orientations, etc. To evaluate the accuracy achieved with the algorithm, we use a reference DEM 2 m × 2 m (DEM_ref) from which the derived DEMs are obtained at 4 m × 4 m, 8 m × 8 m and 16 m × 16 m (DEM_der). For each DEM_der its spline approximant is calculated, which is evaluated at the same points occupied by the DEM_ref cells, getting a resampled DEM 2 × 2 m (DEM_rem). The horizontal accuracy is obtained by computing the area amongs the homologous contour lines derived from DEM_ref and DEM_rem, respectively. It has been observed that the planimetric errors of the proposed algorithm are very small, even in flat areas, where you could expect major differences. Therefore, this algorithm could be used when an evaluation of the horizontal positional accuracy of a DEM product at lower resolution (DEM_pro) and a different producing source than the higher resolution DEM_ref is wanted.