Country Specific – Germany

The elevation model for Germany in SCALGO Live is based primarily on BKG's DGM5 as well as DGM1/2 in states where these are available as open data:

• Bayern DGM1
• Berlin DGM1
• Brandenburg DGM1
• Hamburg DGM1
• Hessen DGM1
• Nordrhein-Westfalen DGM1
• Sachsen DGM1
• Sachsen-Anhalt DGM2
• Schleswig-Holstein DGM1
• Thüringen DGM1

To accommodate resolutions down to 1 m, all analyses are done in 1 m resolution for the whole country in ETRS89/UTM32.   The vertical reference used is DHHN92.  Workspaces constructed from this model also have a resolution of 1 m. We strive to keep the model up to date with the latest sources.

In order to use an elevation model for hydrological analysis of surface water, such as watershed and flow accumulation computations, three conditions need to be met:

• The upstream area of any river should be covered by the elevation model.
• Structures on top of the terrain should only be present in case they actually block water from flowing under or through them.
• Structures transferring water below the terrain surface should be taken into account.

Below, we discuss how we process the model to fulfill these conditions as well as possible.

Extensions

In order to cover the upstream areas of all rivers crossing the country, we have extended the model in the following areas:

• For Switzerland, contributing almost entirely to the Rhein, we use the 0.5 m swissALTI3D model (resampled to 1 m) from the Federal Office of Topography swisstopo.
• For Austria's contribution to the Donau, we use the 10 m Digitales Geländemodell Österreich.
• For Poland's contribution to the Oder, we use the 1 m Digital Terrain Model made available by the Head Office of Geodesy and Cartography (GUGiK).
• For France's contribution to the Mosel and Rhein, we use the 1 m RGE Alti model.
• To cover minor streams on the border with Denmark, we use the 0.4 m Danish elevation model (DHM) (resampled to 1 m) produced by the Danish Agency for Data Supply and Infrastructure (SDFI).
• Similarly for the Netherlands, we use the 0.5 m Dutch elevation model AHN4 (resampled to 1 m).
• For Luxembourg's contribution to the Mosel, we use the 0.5 m MNT LiDAR 2019.
• To cover remaining areas of the Czech Republic, France, Luxemburg and the Netherlands that contribute to flow in Germany, we included data from the 30-meter EU-DEM data set, which in turn is based on SRTM and ASTER GDEM data.
  

A full overview of which data source is used for which part of the model is available by clicking the gear icon next to an elevation layer, selecting the "Source" tab, and "Show source information". Use point query to see more details for individual areas. Multiple styles are available for this layer to colour sources by e.g. date and resolution.

Buildings

Buildings are not included in the terrain models, since they represent the "bare earth" elevations. When computing water flow paths, more realistic results are generally obtained when the elevation model does include buildings so water can be simulated to flow around them. In SCALGO Live, we accomplish this by adding buildings back into the model using a data set of building footprints, where we raise all grid cells covered by a building to a height 10 meters above the highest terrain point within the building footprint. This model is called "Terrain/Buildings" and is the basis for all nationwide hydrological computations.

The building footprints are taken from the AdV Hausumringe Deutschland (HU-DE) dataset, but exclude footprints of bridges, sluices, weirs, etc.

Bridges, underpasses and hydrological corrections

Major bridges have generally been removed from the models, but for many smaller bridges and underpasses additional hydrological corrections that allow water to flow through such structures are necessary. SCALGO Live Germany includes a nationwide hydrological correction set based primarily on the Basis-DLM data from BKG. Corrections have been generated at intersections between buildings and rivers lines, and river sections marked with the "HDU_X" property, indicating the river is flowing under something. Each correction thus follows a line in the river network, with end points adjusted to match the elevation model as well as possible.

The set of corrections is available under the Hydrological Corrections category in the Library.

The national analyses use these corrections, and workspaces created using the predefined "Flash Flood Map" or "Sea-Level Rise" buttons also include them by default. If you create a workspace through any other means than the predefined buttons (e.g. if you upload your own model), you can include corrections in that workspace through the workspace Actions tab by clicking Import corrections; they will not be included automatically.

Land use data

SCALGO Live uses the CORINE Land Cover 5 ha (CLC5-2018) from BKG for watershed land use queries. This dataset is based on the Landbedeckungsmodell Deutschland 2018 (LBM-DE2018).