Precision assessment of stereo-photogrammetrically derived facial landmarks in infants

In order to examine the suitability of an anthropometric imaging device for a particular study population, it is necessary to assess measurement error on members of the population.

We provide an analysis of the precision of a stereo-photogrammetric tool in locating 3D landmark coordinates on images of infants and present the results in a way that facilitates direct comparison with some of the precision results found in the literature.

Intra- and inter-observer precision are examined for 26 landmarks on 21 infants. Mean absolute differences for landmark coordinates and linear distances, mean landmark coordinate errors, and relative errors of magnitude are calculated.

Relative error of magnitude is less than 4% for the majority of intra- and inter-observer inter-landmark distance comparisons. Landmarks lying on the midline of the face and on smooth regions with gentle curvature, in particular the sellion, glabella and nasion, have relatively low precision.

Our precision values compare well with those reported in published studies on landmark location in 3D surface images.