Slope
The «Slope» plate calculates the steepness of the terrain at every point of the height grid and divides it into 5 colour steps.
Overview
Contour lines show height; slope shows steepness. «Terrain» and «Slope» are drawn from the same height grid. Where contour lines are close together the terrain is steeper, but reading the spacing by eye gives different results. The «Slope» plate divides steepness into steps with fixed values and fills them as colour areas.
Berlin and Cologne are mostly flat on the plate. In Stuttgart the city centre lies in a valley basin with steep slopes; there the plate uses all steps.
Contents of the plate
| Element | Content |
|---|---|
| Colour areas | 5 slope classes |
| Water | Light blue, above the colour areas |
| Colour | Another accent colour changes only the hue; the lightness of each step stays |
| Note | Always states the 50 m smoothing and the maximum and mean slope |
The colour areas do not show which side of a slope is higher. The direction of the fall is read on the «Terrain» plate of the same site.
How to use
- Find steep and flat areas around the site in the colour areas
- On the «Terrain» plate, check in which direction the terrain rises
- Check the access side and its slope (it determines the position and length of an underground car park ramp)
- Find steep parts within the site (they determine where the building can stand)
- Compare with the sun hours of the same site
Method
| Item | Content |
|---|---|
| Height data | DGM1 of the federal states, averaged to 5 m for sitedia, the same grid as «Terrain»; outside the state data, Copernicus DEM GLO-30 |
| Height reference | Height relative to the centre of the site (the absolute height is not used) |
| Slope | Derivative of the height differences in the east-west and north-south directions at every grid point |
| Smoothing | 50 m (fixed, in metres) |
| Classes | 5 · 10 · 15 · 20° (5 steps) |
Classes
The Germany edition uses degrees. In percent: 5° ≈ 8.7%, 10° ≈ 17.6%, 15° ≈ 26.8%, 20° ≈ 36.4%.
| Class | Meaning for design |
|---|---|
| under 5° | Practically level; the slope does not shape the layout |
| 5–10° | Gentle slope; can be handled with split levels or a raised ground floor |
| 10–15° | Sloping ground; layout and access follow the terrain |
| 15–20° | Steep; retaining walls, cut and fill become part of the design |
| from 20° | Very steep |
50 m smoothing
Slope is the derivative of height, so small noise in the height data is amplified. Without enough smoothing, level ground fills with false patches. 50 m removes most false patches and keeps real slopes; at about 100 m, real steep slopes are smoothed too. The width is fixed in metres, not in grid cells, because the grid spacing changes with the radius (6.2 m at 300 m, 16.7 m at 800 m).
Limitations
The effective resolution of this plate is 50 m. Cuttings, retaining walls and embankments narrower than 50 m do not appear.
Terrain, not surface
DGM1 is a terrain model: buildings and trees are removed, so tall buildings do not appear as hills. Bridges, embankments and retaining walls can remain as steep strips. Outside the state data, the plate falls back to Copernicus DEM GLO-30, a surface model with a 30 m grid.
Not a topographic survey
The plate is for reading the shape of the terrain in the design stage. Heights for design, drainage or ramp gradients need a topographic survey.
Data sources
- Heights: Digital terrain model DGM1 of the federal states (Geoportal Berlin and Geobasis NRW: dl-de/zero-2.0; LGL Baden-Württemberg: dl-de/by-2-0, Datenquelle: LGL, www.lgl-bw.de), averaged to 5 m for sitedia · outside the state data Copernicus DEM GLO-30 (produced using Copernicus WorldDEM-30 © DLR e.V. 2010-2014 and © Airbus Defence and Space GmbH 2014-2018 provided under COPERNICUS by the European Union and ESA; all rights reserved)
Related guides
Example plates: Geoportal Berlin (dl-de/zero-2.0) · Geobasis NRW (dl-de/zero-2.0) · Datenquelle: LGL, www.lgl-bw.de (dl-de/by-2-0) · © OpenStreetMap contributors (ODbL)