2The digital elevation model represents the bare ground surfacewithout any objects like plants and buildingsA digital elevation model (DEM) is a digital representation ofground surface topography or terrain.A digital elevation model (DEM) is defined as "any digital representationof the continuous variation of relief over space,“ Burrough, 1986Digital Elevation Model (DEM) is a grid where each cell is a valuereferenced to a common datum (sea level), Aronoff 1989
4In some definitions a DTM is the same as a DEMDTM is defined as spatial distribution of terrain attributes, atopographic map in digital format, that not only consist of theDEM but also slope, aspect and so on… (Meijerink, A. M. J., DeBrouwer, H. A. M., Mannaerts, C. M. & Valenzuela)What’s more important; be aware that there are different definitions!
29 6 7A 2 4 5 8 9B 3 10 11 1 Center of the dike
301200 km of dikeEvaluate every 0.5 meterRetrieve 11 heights> 26 million queries… from a dataset with 7 billon pixels (30GB)Read each time only the extent of 1dike into memory. Hours of processingtime reduced to minutes!
31height ≥ AB ≤ height < Aheight< BInsufficient dataNo Data
32 More than 1.5m, AHN2 > A More than 70% NoData AHN2 < BInsufficient data, less than 70% NoData, More than 1.5m, B <= AHN2 < Abut no 3 consecutive points with data
33height ≥ AB ≤ height < AB-10cm ≤ height < BB-20cm ≤ height < B-10cm height ≥ AB-30cm ≤ height < B-20cm B ≤ height < AB-40cm ≤ height < B-30cm height < Bheight < B-40cm Insufficient dataInsufficient data No DataNo Data
34 Sections of 100mDEMDike center line Cross profile H100min Standard profile 3D dike profile