ABSTRACT
Modern urban areas are places of continuous change. Over months, buildings may be torn down and new ones started; streets can be altered and new ones constructed; railways or other means of urban transport may change. The models of urban areas must be able to accommodate these changes. This is especially so since models are significantly higher resolution than previously and cover wider areas. Now models can typically have imagery and elevation data at resolutions of one foot to one meter with certain features (on key buildings, for example) that may be at higher resolution. At these resolutions and for certain applications, even small changes can be noteworthy.
