The outcome of the project has been successful from the interpolation perspective, where the final results have shown major improvements over the original rasters, and a multitude of possible other interpolation methods have shown potential. In the end, the algorithm used to create the gridded DTM was
based on Startin’s Laplace interpolation and for DSM a Python implementation of quadrant-based IDW was used. The Startin Laplace method gives statistically good results while running quickly on it’s Rust base, though using quite some memory. The quadrant-based IDW has proven to be the best way to interpolate results which include the buildings, creating crisp edges without too many artefacts. Fur-
thermore, the introduction of a polygon water flattening step was essential to prevent no-data values where water bodies prevented for accurate interpolation. The long-shot goal of being able to process all the tiles for the Netherlands was missed by a lot, eventually choosing to interpolate a series of tiles neighboring Delft to create a contiguous result set. Zuid-Holland has therefore only been partially completed, whereas the expectation was to be able to complete this area with ease in three days. An initial overview of the comparison for a single tile in Rotterdam (37HN1), can be seen in Figure 1.3 for the DTM results and Figure 1.4 for the DSM results.