Evaluation of Kriging interpolators and Topo to Raster for the generation of Digital Elevation Models from a "as built"

This work evaluates the use of Kriging and Topo to Raster interpolation methods in the generation of Digital Elevation Model (DEM) from the bottom of a Water Treatment Station decantation box raised with total station. For the Topo to Raster interpolation two methodologies were used, one using contour lines and quoted points as input file, known as standard Topo to Raster, and another using only quoted points, known as conditioned Topo to Raster. The Kriging interpolation was done using ordinary Kriging and simple Kriging. The DEM generated by the Triangular Irregular Network (TIN) was used as reference. From the isobathymetrics extracted from the DEMs, values were extracted from the interpolated variable and discrepancies were calculated regarding the reference. Statistical indicators were calculated for each discrepancy sample. The model generated by the conditioned Topo to Raster presented visible distortions in the study area edges and center, and must be discarded. Applying the z test, it's concluded that Kriging and standard Topo to Raster interpolators, applied in small surfaces interpolations, do not differ. For average depths of 3,21m, the following statistical indicators values were found: average discrepancy of 1cm, maximum discrepancy of 10cm, standard sample deviation of 3cm and RMS discrepancies of 3cm.

Keywords:
Geostatistics; RMS; Decantation box