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JPT Nº12  Sponsors & Supporters

INTRODUCTION

 

Digital three-dimensional (3D) models continue to revolutionize paleontology. They allow archiving, analyzing, and visualizing specimens that would otherwise be difficult or impossible to access, and can protect delicate specimens from handling. Many methods exist to create 3D-datasets, such as laser scanners, reflective light scanners or computation from tomographic data sets, e.g., computed tomography (CT) scans. For an extensive review of current methods see Sutton et al. (2014).

Over the last few years, photogrammetry has revolutionized the digitizing process for surface topography. The process involves taking a series of photographs of an object from different angles to computationally generate a 3D model by comparing features across the photographs. Incidentally, Sutton et al. (2014) recommend photogrammetry as the first method  of  choice  for  all surface-only  3D digitizing. As a proven and affordable alternative to laser or structured light scanning, photogrammetry is increasingly becoming the method of choice for paleontological research. Done correctly, it not only delivers highly accurate and (if so desired) textured models, but  is  also  user-friendly,  relatively  fast  and inexpensive. Here, we provide a simple introduction to the practical application of photogrammetry for paleontology and other specimen-based research  disciplines  dealing with specimens in the centimeter-upward range.

Applications for photogrammetry involve many different fields, including topographic mapping, engineering, manufacturing, quality control, architecture, movie production, police investigation (i.e., collision engineering, crime scene documentation), archaeology (e.g. De Reu et al. 2013), meteorology as well as geosciences.

Depending on the photographic method used, the  potential     maximum     resolution     of photogrammetry varies  considerably.  At  the extreme, scanning electron microscope (SEM) photographs can be employed to  create models at   nanometer   resolution   (Piazzesi,   1973; Kearsley et al., 2007). The typical usage in  paleontology  involves  consumer  to  high-end professional DSLR cameras. The resolution of a model depends on the resolution of the sensor and the distance between the sensor and the object. High megapixel DSLRs  allow creating models with a resolution measured in tens to hundreds of micrometers. Falkingham (2012) found   that   even   a   camera   with   only   8 megapixels allowed him to produce models with an accuracy significantly better than 0.3 mm. Because the data capture for photogrammetry is usually performed via a conventional DSLR camera,  the  method  is  very  versatile  and mobile. Taking photographs is usually possible in practically any place where paleontological specimens are located, be it the field, collection rooms, or exhibitions. Direct physical access is not required (although it often is helpful, and given the ability to use a tripod and a suitable telephoto lens even specimens that are far out of reach can be digitized satisfactorily for most research purposes.

Here, we present techniques for photography and image handling in photogrammetry software that are adapted for typical use cases in paleontology. Naturally, they can be applied to other fields of research as well, including e.g. archaeology and art history, as long as the specimens   of   interest  are similar to paleontological objects.

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