Close-Range Photogrammetric Measurement and 3D Modelling for Irish Medieval Architectural Studies

In Ireland, as in much of Europe, church architecture of the late medieval era is considered by architectural historians to have been designed according to specific geometric principles and methods. Research into such structures and their design methods has traditionally involved visually-based stylistic comparison of features, primarily by visual techniques. In recent years, however, more analytical approaches to these studies have developed and these procedures require accurate documentation of buildings and features. 3D models generated by a number of close range measurement techniques (terrestrial laser scanning (TLS) and photogrammetry) are appropriate for use in such studies. However, since historical research frequently requires the comparison for large numbers of objects and/or buildings, it is essential that the methods used are easily available and are of low or medium cost, while still being appropriate in terms of accuracy, speed and usability. For the typical multi-site architectural historical study TLS is too expensive and too complex in terms of data collection, software processing and data management. This project evaluated the suitability of a close-range measurement method for 3D modelling of medieval architecture comprising a non-metric digital camera (Nikon D70), a reflectorless total station (Leica TPS 1205) and software for stereo modelling. Stereo models suitable for the extraction of 3D details of medieval window tracery (an important stylistic and dating feature) were generated and each stage of production analysed. This paper presents preliminary results of investigations into the suitability of this method for use in Irish medieval architectural historical studies and finds that low-cost methods are capable of achieving sufficient levels of accuracy without being onerous in terms of time spent or user inputs.