Cl PA 2003 XIX th International Symposium, 30 September - 04 October, 2003, Antalya, Turkey 
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Figure 4. The upper scaffolding level was used for scanning 
3.1 Topographic Survey 
In order to realise a stereoscopic restitution of the Hermes 
statue, it was necessary to define a set of control points with 
coordinates inserted in a local reference system. A classical 
topographic survey by intersection method was performed using 
a Leica TCR307 total station (accuracy of angular 
measurements 1” and ±2mm±2ppm in distance). The total 
station has also the capability to work in a reflectorless mode 
with a degradation in the distance measurements. A traverse of 
six points on the ground floor and eight targets evenly 
distributed around the walls of the room where the statue is 
housed, were measured with a redundant number of readings. 
This ground control system was used to determine the reference 
system of the control points of the photo stereopairs (described 
in §3.2). An arbitrary system of coordinates has been adopted 
with the Z-axis having its origin at point 01 and abscissa axis 
formed by ground point 01 and wall point 2 (Figure 5). The 3D 
least squares adjustment resulted to point accuracy within 3mm 
at 95% confidence level. The coordinate system defined with 
this procedure gave also the georeference of the 3D model 
obtained with the laser scanning data. 
Figure 5. Schematic of the control network (not to scale) 
3.2 Photogrammetric Data Collection 
The photogrammetric images were taken independent of laser 
scanning data collection. From each location, photographs were 
taken by two cameras: 
• An analog semi-metric camera, Hasselbland C/M 500, format 
5.5x5.5 cm 2 and focal length c = 50mm. The mean distance 
from the object was about 1,60m so that the scale of the 
photos should be about 1:30 (final accuracy specifications for 
the coordinates of the detail points was 0.8mm<lmm) 
• A digital camera, Sony DSC-F707 with 2560x1920 pixels (5 
Mpixel with pixel size about 4pm) and zoom capability x5. 
The photos were taken always with the minimum zoom, with 
c=9.7mm given by the manufacturer, and the output was in a 
TIF format. The mean distance from the object was 1.80m, so 
that agreement could exist with the imaged scenes of the 
analog and digital photos. 
The dual photography was performed exclusively for research 
purposes, so that a comparison of the results of such a complex 
object derived from photos of different type cameras could be 
studied. It should be noted that none of the two cameras is 
metric and their inner orientation data through a laboratory 
calibration are not known. 
With each camera, 43 photos were taken in total, which create 
22 stereopairs, that is: 
• 8 photos, one stereopair for each of the four sides of the base 
of the sculpture 
• 32 photos for the body of the sculpture. The sculpture was 
divided for practical reasons into two parts, lower and upper. 
One stereopair (2 photos) was taken for each part, along each 
basic direction (forward, backward, left and right) and one 
stereopair (2 photos) along each diagonal direction. In total, 2 
photos were taken for 8 directions at 2 parts, thus 32 photos. 
Figures 6a and 6b show the left and right images of the 
stereopair, taken along the direction forward-right diagonal 
for the upper part of the statue. The details of the body of 
infant Dionyssos, which are not pictured on other stereopairs 
emphasise the importance for performing such a multiple 
photographic coverage of the body of the sculpture 
• 3 photos, in two stereopairs, for the coverage of the statue 
from the top (cf. Figure 3). 
The most difficult part during the photogrammetric data 
collection was the establishment of control points, mainly due 
to the sensitivity of the object being captured. There were 
several methods tested prior to photogrammetric collection, 
with the assumption that any physical contact with the sculpture 
was not allowed. The most appropriate method proved to be the 
projection through a video projector of a laptop computer 
screen showing a predesigned grid of lxlcm 2 that was covering 
the surface of the sculpture from each location of the 
photographic shooting. Simultaneously, the coordinates of 
selected nods of the grid were measured from a pair of stations 
that were established close to the sculpture. This method was 
nevertheless, rejected by the authorities of the museum. It was 
considered that this technique possibly causes damage to the 
surface of the marble by producing spots due to continuous 
exposure to the projector’s light for the duration of few minutes. 
The most efficient method finally implemented, was the 
placement of 6-12 predefined targets (square black and white) 
on light wooden frames or sticks that were placed adjacent to 
the part of the statue to be photographed. There was an effort to 
locate the wooden sticks in such a way so that the attached