Over the past
two decades or so, 3D digitization of vertebrate fossils has become increasingly
common, and nowadays 3D surface models are widely used for research, exhibition,
and archiving purposes. Various digitization me-thods exist, the ones most
commonly used in vertebrate paleontology probably being x-ray CT (including
micro-CT), laser scanning (stationary or hand-held), and photogram-metry. This
variety presents the researcher with the difficult decision of which method to
choose for their specific purpose. For reviews of the individual methods
including their history, applications in paleontology, advantages and limits,
see Mallison (2011) and Sutton et al. (2014).
The aim of this study was to compare two major methods, photogrammetry and
micro-CT scanning in terms of accuracy, reproducibility, and efficiency, and
thereby to help researchers choose the appropriate method for their purposes.
Accuracy and reproducibility were assessed by testing for three aspects: 1.
similarity of surfaces generated from micro-CT scans vs. photogrammetry, 2.
inter-user error when surfaces are reconstructed from the same data set
(micro-CT) using different computer programs and settings, and 3. error when
using the same method (photogrammetry) on photo-graphs taken by different
people. Efficiency was addressed by evaluating the duration of individual steps
of surface generation, and by also taking into account the costs and the
learning process of the different methods.
We chose to use this particular specimen, a cranium of an early Oligocene
bothriodontine anthracotheriid, because it represents the kind of object
vertebrate paleontologists typically have to deal with when generating 3D
surfaces: skulls and skeletons, or parts thereof. These highly complex objects
feature foramina, fossae, processus, and sharp cristae that contain a lot of
morphological information. Detailed visualization of this information in the 3D
model is usually crucial for subsequent morphometric or other analyses. Our
specimen is intermediate in size between very small (e.g., micromammals) and
very large vertebrate fossils (e.g., dinosaurs), and thus serves well as a
general model specimen.