SCALGO Live Documentation

Notes on the Denmark/2015 model

At the end of 2015, the Danish Geodata Agency released a new Danish elevation model. The 2015 model has a horizontal resolution of 0.4 meters, much higher than the previous model from 2007 where the resolution was 1.6 meters. This model is available in SCALGO Live under the name Denmark/2015. There are a couple different variants of the model available.

Denmark/2015/Buildings: This is the raw model enriched with building footprints from the national GeoDanmark dataset. For each GeoDanmark building footprint we raise the elevation of the cells whose center is inside the building 10 m relative to the highest elevation value of the original Denmark/2015 model.

The 2015 model with GeoDanmark building footprints.

Denmark/2015/Rain and Denmark/2015/Sea: Both of these models are derived from the Denmark/2015/Buildings model and include the set of hydrological corrections put out by the Danish Geodata Agency (DHyM/Tilpasninger). The Denmark/2015/Rain model includes the corrections made for modeling water flowing downstream on the terrain (e.g. water from rain events) while the Denmark/2015/Sea model is targeted for modeling flooding coming from the sea (the chief difference between the two being the opening or closing of sluices and similar infrastructure in the model). However, it is important to understand that these corrections were generated for the 1.6 m terrain model from 2007. This has several important implications, some of which are: (i) Changes to the terrain that have happened after the generation of the 2007 model are not corrected. (ii) Some of the corrections no longer accurately capture the feature they are trying to correct due to slight shifts in georeferencing and the increased resolution. However, even with those caveats, the corrected models are still significantly better for hydrological purposes than the base model would have been, for the majority of locations. A new set of corrections targeting the 2015 model is currently being produced and the models and derived computations will be updated when they become available, probably sometime in early 2017.

A correction from the 2007 model incorporated into the 2015 model.

Some technical details: There are two types of corrections in DHyM/Tilpasninger: single line segments with elevations at the end points, and so-called "horseshoes" representing areas to be interpolated from two opposite sides of a quadrilateral. For ease of manipulation in commercial GIS tools, the second type of corrections were also represented as series of line segments with end point elevations for the production of the 2007 models. Since this representation depends on the resolution of the model and included elevation values from the old model, we have chosen to use the horseshoe (quadrilateral) representation directly and interpolate between the sides using elevations sampled from the 2015 model. Furthermode, DHyM/Tilpasninger contains corrections that are intended to correct issues in the 2007 model, these corrections (with names prefixed by DHMFix) were not included in our 2015 models.

Road infrastructure constructed after 2007 and therefore not addressed by the 2007 corrections resulting spurious sinks in the Denmark/2015/Rain and Sea models.