Optimal methodologies of interpolation for the DTMS

Digital terrain models are key tools in land analysis and management as they are directly employable in GIS systems and other specific applications like hydraulic modelling, geotechnical analyses, road planning, telecommunication… TIN generation, from different kind of measurement techniques, is already ruled by specific regulations while interpolation techniques, to compute a regular grid from a TIN, are still lacking. A shared methodology has not already been developed in order to be used in cartographic production while generating digital models. Such ambiguity obviously involves non univocal results and can affect precision that can lead to divergent analyses on the same territory. In the present study different algorithms will be analysed in order to spot an optimal interpolation methodology. The availability of the recent digital model produced by the Regione Piemonte with airborne LIDAR and the presence of sections of testing realized with more elevated resolutions and the presence of independent digital models on the same territory, allows to set a series of analysis with consequent determination of the best methodologies of interpolation. The analysis of the residuals on the test sites allows to calculate the descriptive statistics of the computed values: all the algorithms have furnished interesting results, but the best results is achieved by the employment of the IDW (Inverse Distance Weighing). Moreover, a comparative analysis will be carried out, by interpolating data at different input point density, with the purpose of highlighting thresholds in input density that may influence, in the interpolation phase, the quality reduction of the final output.