City models can be made using a range and combination of techniques.   These range from traditional models based on street level photographic surveys to advanced remote sensing data collection, such as laser scanning.  There is continuous research being carried out into automatic and semi-automatic 3D modelling as well as procedural modelling, for the creation of fast, accurate and photorealistic building models.

Photogrammetry   This is an established remote sensing technology that involves using stereo aerial images to pick out building geometry and calculate their elevation.  City models are then created by integrating this geometry with cadastral information to model buildings from their building footprints.  Terrain data can be integrated into the model, and building texture maps added by site photography for photorealistic building models.  This describes a range of techniques and processes.

LIDAR   (Light Detection and Ranging) A remote sensing technology that is used to collect both building and topographic data. The geometry acquired by this method normally needs significant refinement, but is useful for gaining large quantities of accurate building data.  This is often used to extract accurate building heights that is used as a reference to accurately extrude building footprints and create a simple massing model.

Terrestrial 3D HDS (high definition surveying) laser scanners are used to capture accurate geometry that is then used to create buildings.  This is a time-consuming process but achieves very accurate and detailed results.  Much research is currently being carried out to produce semi-automatic modelling from the laser data. In the case of the Glasgow city model, a team of 7 modellers would typically model a photorealistic building in 2 days, after completing up to 8 scans per day, covering the equivalent of 2 city blocks (see Glasgow).

Manual Survey   Building geometry is surveyed or acquired from existing plans and modelled in 3D using a suitable 3D CAD drawing package.  This traditional process can be extremely time-consuming and requires collecting accurate building measurements in order to model a building, or to calibrate photographic images for accurate measurement extraction.  However, this method is used by almost all urban modellers to some extent, for collating textures, calibration, verification of existing models, etc.

GPS surveys are a common method of collecting topographical features for a city model.  This involves collecting latitude, longitude and elevation (x,y,z) information at multiple positions around the city using a large portable GPS device.  This data is stored and used as a base layer for an urban model upon which properly located buildings can be applied.

Automatic, remote sensing   much research is being carried out in this area, particularly by Microsoft and the OS. This involves a combination of advance data capture hardware that collects a range of data (photographic, LIDAR, Infra-red) and powerful software that can identify architectural features and automatically produce 3d building and city models.

Procedural modelling  involving the semi-automatic creation of detailed city models, procedural modeling uses a system of grammar based techniques for efficiently creating large urban models.  The latest methods are being used to reconstruct buildings from aerial and street level imagery to accurately model buildings.