P. Schrott's research while affiliated with Budapest University of Technology and Economics and other places

Facial reconstruction is the process of reconstructing the geometry of faces of persons from skeletal remains. A research group (BME Cooperation Research Center for Biomechanics) was formed representing several organisations to combine knowledgebases of different disciplines like anthropology, medical, mechanical, archaeological sciences etc. to computerize the face reconstruction process based on a large dataset of 3D face and skull models gathered from living persons: cranial data from CT scans and face models from photogrammetric evaluations. The BUTE Dept. of Photogrammetry and Geoinformatics works on the method and technology of the 3D data acquisition for the face models. In this paper we will present the research and results of the photogrammetric network design, the modelling to deal with visibility constraints, and the investigation of the developed basic photogrammetric configuration to specify the result characteristics to be expected using the device built for the photogrammetric face measurements.

In this publication, the concept of image coordinate RMS error derived from average object side RMS is introduced. In the course of derivation, data on network geometry and redundancy were taken into consideration; thereby camera output for a given object distance was characterized by this quantity independent of the shooting arrangement. If this value is determined for several object distances, a function of average image coordinate RMS error vs. object distance is yielded, which, in our opinion, properly characterizes the photogrammetric potential of a given camera. This function was determined - using new measurement results - for a mobile phone with a camera and a digital camera frequently applied in our days; in addition, it was generated for a professional camera used in the 1990s, KODAK DCS, by using former results.

A new multidisciplinary project extending over a number of years was initiated in Hungary to combine knowledgebases of different disciplines like anthropology, medical, mechanical, archaeological sciences etc. to computerize the face reconstruction.. A research group (BME Cooperation Research Center for Biomechanics) was formed representing several organizations that are cooperateing during the project period. In this paper we will show the first results of our work: the examination of the possible data gathering methods from special aspects. First the data collecting method has to be able to produce geometric 3D data of the cranium of damaged/mummified subjects. Second, the software development requires huge dataset of 3D face and skull models, which could be produced from living persons, so the method have to be capable to mass data collection. Since any modification of the process during the gathering period can result inhomogeneous database, the accuracy and the feasibility of the measuring methods is highly important.

Mobile phones with cameras enable us to take photos of any objects at any time. The question arises whether this new device of communication can play a role in obtaining geometric data and what accuracy demands can still be satisfied by this device. Our series of experiments essentially involve taking photos of a geometrically defined area and examining the degree of likelyhood of the photogrammetric solution to the known geometry. This study was extended to various cameras, the number of points with known co-ordinates, the number of shots, and the object distance which has a decisive impact on picture scale. Furthermore, we compared the accuracy values of the results yielded by the processing of images taken by mobile phones with cameras and by other cameras. Numerical results are disclosed in a tabular format and the conclusions to be drawn from the numbers are summarized.