First, let’s explain two terms:
- DEM (digital elevation model), which should refer to a bare-earth altitude
- DSM (digital surface model), which captures the highest solid surface (including built-up objects or even dense grown vegetation)
Solargis database features DEM terrain surface data (even though in some areas the noise from vegetation cover may be captured). The nominal resolution is 90 m, which is satisfactory for the regional analyses of the terrain structures in the neighbourhood (for example shading from surrounding mountains or hills).
For city models, DSM (digital surface model) is preferred, preferably in a sub-meter resolution. For detailed shading analyses of the roof PV, DSM model with a nominal resolution of about 10 cm or similar is recommended. Nowadays, there are no global DSM models in such high resolution available. However, there are regional activities to create country-wide products. Solargis models are capable to use high resolution data and compute solar resource and PV potential for the roofs of the entire city. However, in such case the computing capacity rises significantly, therefore such analyses are performed for limited areas.