3D city model
3D city models are more than the simple evolution of paper maps. Accurately mapping a 3rd dimension provides a cornerstone dataset for a number of industries, and 3D city models already play a role in planning and architecture. This role will continue to evolve, as planning for future urban transport systems, smart cities and even AI-driven energy-saving systems will all rely on accurate 3D city models.
 Extruded footprint polygons
Extruding buildings footprint polygons is one way of adding a third dimension to 2D mapping data. In essence, the technique is taking an estimate of a building’s height and extending the footprint vertically to that height.
Digital surface models (DSM) can be created by pixel-matching of aerial photography or by creating a mesh from an airborne LIDAR. Taking raw LIDAR data and turning it into a 3D model with no additional information, such as a building’s polygons, is an essentially automated process. Users can download the source data in the raw LAS format to create DSMs).
 3D city models by Google
Structure-from-motion (SfM) pipeline for visual 3D modelling of a large city area uses a 360° field of view Google Street View images. The core of the pipeline combines techniques such as SURF feature detection, tentative matching by an approximate nearest neighbour search, relative camera motion estimation by solving five-point minimal camera pose problem and sparse bundle adjustment.Photogrammetry Models
Manual stereo photogrammetry is generally accurate and detailed. The 3D models produced are usable and, once the project is set-up, various levels of detail can be captured. There are several way to collect source data, but the downside is that it’s a manual process and can be expensive in terms of time and resources.
Civilian satellites currently offer limited use in major world cities, but with better resolution available, it should be possible to substitute aerial surveys for satellite surveys in the foreseeable future.
 Manual aerial photogrammetry
3D London model by AccuCities is one example of a large 3D city model captured using stereo photogrammetry from fixed-wing aircraft. These 3D models can be captured and delivered as AutoCad, Sketchup or FBX files and can be directly imported into 3D editing software.