Developments in Close-Range Photogrammetry for 3D Modelling: the iWitness Example

Close-range photogrammetry is increasingly being employed for 3D measurement and modelling across a host of application areas. Consumer-grade digital cameras are becoming ubiquitous, and ‘professional ’ digital cameras are becoming less expensive. Thus, access to suitable imaging technology for 3D measurement and subsequent model building and visualisation is now open to all. Access to suitable photogrammetric data processing systems is, however, still less than universal. Although there are a number of PC-based integrated image measurement and photogrammetric restitution systems available, for both multi-image processing and stereo configurations, most are either too specialised for the casual user, too expensive or too difficult to use without extensive training. This paper reports upon a new photogrammetric data processing system, iWitness, which has been especially developed for the non-specialist user. Indeed, its primary application domain is accident reconstruction and forensic measurement where it is used by police. The system is also ideal as a tool for many other 3D measurement tasks in engineering and architectural photogrammetry, as well as in general heritage recording. The iWitness system is characterised by a new paradigm adopted within the image measurement and photogrammetric processes. This is centred upon fully automatic on-line photogrammetric processing, automatic recognition of the camera(s) from the imagery, extensive operator assistance as exemplified by guided referencing and interactive quality review, as well as exceptional ease of use. The paper describes iWitness and illustrates its flexibility and accuracy. The iWitness software is low cost, and offers the user the prospect of assembling a photogrammetric measurement system comprising camera and all necessary data processing software, which is capable of accuracies to about 1:20,000, for as little as $US 1500