3D Imaging is commonly done by one of two ways, 3D laser scanning or photogrammetry. Regardless of the data acquisition method, these tools allow for the accurate capture, manipulation and visualisation of an object or landscape in three dimensions (or four dimensions if repeated over time). From this, many types of end products are possible including static CAD/GIS files, 2D images, interactive 3D images, fly through movies, 3D prints and, recently, virtual reality immersion.
Photogrammetry uses complex computer algorithms to digitally stitch together several digital images to form a 3D rendering. This can be done in a very simple (and cheap) way with modern smart phones, though accuracy will be poor. For high accuracy, a proper camera that has been calibrated for the task is necessary. With high quality camera equipment and a well-conceived method of capturing the target from many angles, high resolution 3D models can be achieved. Photogrammetry has been used in archaeology and cultural heritage for decades but technological improvements in the 1990s have drastically increased use of the technique. Recently, Structure from Motion (SfM) and automated Computer Vision techniques have expanded the possible applications of photogrammetric techniques as precise location information for each digital image used in the model is not required.
3D laser scanners emit a pulse of light and measure how long it takes for it return to an onboard sensor. Each pulse provides the 3D coordinates for a very small part of the surface of the target by recording the time it takes the laser to return to the instrument. Using a predetermined routine, laser scanners can collect millions of such readings in a few minutes producing a point cloud of data. The point cloud is a 3D map of the object or area scanned. The denser this point cloud is, the more accurate the final 3D rendering will be. 3D scanning has been used in archaeology and heritage management since the late 1990s.
The speed and accuracy of modern laser scanners, and their ability to work in complete darkness, are some of the significant advantages when compared to photogrammetry. However, their cost far exceeds those required for photogrammetric recordation.
3D imaging is fast becoming a regular part of the heritage management process in Australia. It can be used to record important or endangered heritage much quicker and more accurately than traditional methods. Further, their ability to digitally preserve heritage (presumably forever) is often a reason for their use in recording threatened heritage.
Temporal monitoring is another important use of 3D imaging in heritage management for sites or objects that can not be moved but are threatened by near by activities. A 3D image is first recorded prior to any development activities. Then, at regular intervals throughout (or at the end of the development process) additional scans can be collected which are used to assess any damage to the threatened cultural heritage. This ability to quantitatively determine the extent of (or lack of) damage throughout the life of a development project provides heritage managers the ability to adapt management protocols, if necessary, ensuring the preservation of important heritage.
Finally, as 3D images are often very captivating they offer a unique opportunity to share artefacts or landscapes with researchers and the general public which may be too sensitive or remote for general access. This allows researchers to study artefacts and collaborate remotely. When 3D printed, it allows the general public the opportunity to physically interact with accurate replicas of important objects while preserving the originals. When done with cultural sensitivity, this offers an opportunity for all of us to enjoy and experience the diverse cultural traditions of Australia in ways not possible just a few years ago.
Today, 3D imaging is being used to document and preserve individual artefacts, map sites and scan broader landscapes. Here are a few examples from Australia:
Digital Imaging (special issue) 2014 World Archaeology. 46(1).
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Luhmann, T., S. Robson, S. Kyle, S. and J. Boehm 2013 Close-Range Photogrammetry and 3D Imaging. Berlin, Boston: De Gruyter.
Mudge, M., C. Schroer, T. Noble, N. Matthews, S. Rusinkiewicz and C. Toler-Franklin 2012 Robust and Scientifically Reliable Rock Art Documentation from Digital Photographs in A Companion to Rock Art (eds J. McDonald and P. Veth). Chichester, UK: John Wiley & Sons, Ltd. doi: 10.1002/9781118253892.ch36
Westoby, M.J., J. Brasington, N.F. Glasser, M.J. Hambrey and J.M. Reynolds 2012 ‘Structure-from-Motion’ photogrammetry: A low-cost, effective tool for geoscience applications. Geomorphology. 179:300-314. doi:10.1016/j.geomorph.2012.08.021.