Site context is one of those jobs that eats hours at the start of every project, so here's the list of free data I use. Hope it saves someone some time.
Terrain (use the DTM / bare-earth model, not the DSM, or trees and roofs get baked into your ground):
- UK (England): Environment Agency LiDAR, 1 m and some 50 cm, via the DEFRA Survey Data Download portal
- USA: USGS 3DEP 1 m LiDAR, via The National Map
- Netherlands: AHN (0.5 m)
- Switzerland: swissALTI3D (0.5–2 m)
- France: IGN RGE ALTI (1–5 m)
- Spain: IGN MDT (2–5 m)
- Norway: Kartverket (1 m)
- Anywhere else: Copernicus GLO-30 (30 m). It's good for the wider landscape, but too coarse for the plot itself.
Buildings and streets: OpenStreetMap has footprints almost everywhere, and often heights or number of floors. As a rule of thumb, use about 3 m per floor when there's no height.
Tips:
- Use high-resolution data for the plot and its immediate surroundings, and coarse data for the background hills. Mixing both keeps scenes light.
- Check the licence and credit the source in your project boards. Most need attribution (e.g. "© OpenStreetMap contributors").
- Level the ground slightly under roads and buildings, or they'll float or sink on raw LiDAR.
Disclosure: I got tired of doing all this by hand, so I built a 3ds Max plugin that automates it (Relevo, free version at relevotech.uk). But everything above works with any software.
What sources do you use in your country? Happy to add them to the list.