Level of detail (LOD) defines the amount that we abstract real world objects, from raw footprints up to sophisticated 3d models. To help you understand which LOD might be appropriate when you come to download data for your project, here’s our short primer on understanding the essentials.
Level of Detail: 0
This is a building footprint. No height attached, no building parts visible. The vast majority of buildings in OpenStreetMap and open data city models are just that: flat polygons.
These work best for plain maps or 2d analysis.
If we are going to visualise such data in 3d, we’re handling it as follows: check whether levels are present or assume a default of 3 levels. Each level is then rendered 3 meters high.
Level of Detail: 1
This extends footprints from LOD 0 with height information. A building can consist of several parts, each with a different height.
The result looks rather blocky but gives a fairly good impression of the general scenery.
This achieved quality is the balance between visual appeal and performance. That’s why it’s the preferred mode for vehicle navigation and mobile devices. LOD 1 is also the best choice for analysis tasks such as radio wave propagation, line of sight, and fluid dynamics.
Level of Detail: 2
Roof shapes are the most significant improvement for this mode. It requires specific map or 3d software to display properly.
Such models could be generated in real time from footprint polygons, height values and a literal roof description. This would then turn into simple blocks, pyramidal shapes, domes etc.
These models can also be pre-generated as 3d models consisting of hundreds of triangles, making it even more flexible.
LOD 2 works well for 3d visualisation of larger city models as well as surrounding context for models of even higher LOD.
Level of Detail: 3
LOD 3 covers maximum roof details and includes facade details. There is no limit on how much information to put in. Materials (glass, metal, stone, etc.) and photo-realistic textures are very common too.
This mode works best for individual objects of interest, or for movie production. The number of available data sets is very limited and because of size and detail these can be difficult to handle.