The reality of virtual anthropology: Comparing digitizer and laser scan data collection methods for the quantitative assessment of the cranium.

OBJECTIVES: The use of geometric morphometry to study cranial variation has steadily grown in appeal over the past decade in biological anthropology. Publication trends suggest that the most popular methods for three-dimensional data acquisition involve landmark-based coordinate data collection using a digitizer. Newer laser scan approaches are seeing increasing use, owing to the benefits that densely sampled data offer. While both of these methods have their utility, research that investigates their compatibility is lacking. The purpose of this project is to compare, quantitatively, craniometrics collected with a digitizer against data extracted from laser scans using the same individuals and laboratory conditions.

MATERIALS AND METHODS: Three-dimensional (x,y,z) coordinates and traditional inter-landmark distances (ILDs) were obtained with a Microscribe digitizer and 360° color models produced from NextEngine laser scans for 38 adult crania representing five cemeteries from the ADBOU skeletal collection in Denmark. Variance-based tests were performed to evaluate the disagreement between data collected with a digitizer and from laser scan models. Consideration was given to differences among landmarks by type, between ILDs calculated from landmark coordinates, and in morphology for the cemetery populations. Further, the reliability of laser scan data collection was assessed by intra-observer error tests.

RESULTS: Researchers should be aware of the potential error associated with the use of Types II and III landmarks and the limitations on reliability imposed by object-to-scanner placement.

DISCUSSION: This project reveals how laser scans can provide a valuable digital archive of cranial material that can be reasonably exploited for the "virtual" collection of coordinates and the calculation of ILDs.