Electronic supplement to
"Merging local DTMs: HELI-DEM project, problems and solutions"
Politecnico di Milano, Polo Territoriale di Como
This electronic supplement contains high resolution figures. They are provided in one PDF file that can be downloaded and off line printed and read.
The paper presents the extended summary of the Ph.D. thesis of the author, submitted to the Premio AUTeC 2014.
In recent years Italy and Switzerland have produced elevation data with different reference frames, technologies, accuracies and resolutions. The HELI-DEM project aims at developing a unique Digital Terrain Model for the alpine area between these two countries, which has to be produced validating and integrating all the available elevation information. To create a unified DTM, the available data have to be merged together on a common output grid. This procedure, that apparently seems to be simple, implies a sequence of operations that are not so obvious. First of all, data have to be validated, both reciprocally and by external and more accurate data in order to verify their accuracy and the presence of possible global biases or local errors. After that, the validated data have to be aligned to a common reference frame, which should be the official European reference frame. Finally the input DTMs have to be merged on the output grid, trying to integrate both the low resolution and high resolution data. This operation could be very complex, because problems may occur because of the mathematical method adopted, its numerical implementation and because of the large amount of input data. This thesis, carried out for the most part within the HELI-DEM project, will describe the deep analyses and methods that have been performed and applied in order to obtain the goal of the project.
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