CIP A 2003 XlX'b International Symposium, 30 September - 04 October, 2003, Antalya, Turkey
The computation of the interpolated value of distance is
carried our by the formula:
^ _ d t •£, +d 7 -S 7 +d^ - S^ + d 4 -<5 4
d+ d-, + d-x + d.
(5)
Fig. 4 shows some of the many windows available to the
user. Note the one on the left, where the XYZ co-ordinates of
the pixel pointed by the cursor (cross shaped) are displayed in
real time.
where ij are the indexes of the current pixel, 5j are the
distance values to the object points and dj are the distances,
on the image, between the pixel i j and the pixels used for the
interpolation.
Special procedures are foreseen to avoid “edge effects” in
case of relevant discontinuities.
3. THE “SOLID IMAGE MAKER”
3.1 The developed software
In order to create and visualise the solid image and to manage
its first applications, a specific software, named Solid Image
Maker, has been implemented (in Visual Basic 6.0).
This software allows:
• to merge the DDEM (acquired by a laser scanner)
with the corresponding digital image and its
calibration parameters;
• to fill the distance matrix by projection and
interpolation;
• to explore the solid image and to display in real
time the XYZ co-ordinates of each pixel pointed by
the cursor
• to create the 3D model of the object in some
drawing formats (VRML - Virtual Reality
Modelling Language, DXF,...);
• to create an artificial stereoscopic pair of the object.
4. A FIELD TEST: THE TETRARCHI STATUE
4.1 A field test: the Tetrarchi statue
The complete procedure for the construction of a solid image
has been tested, using as a test area the Tetrarchi statue, a
famous sculpture placed in the San Marco’s Square in Venice
(see Fig. 3 a).
The Tetrarchi group, also known as the "Four Moros", is a
marble sculpture on the outside of San Marco’s basilica in
Venice, next to the “Porta della Carta” of “Palazzo Ducale”.
The statue represents, according to tradition, the four
governors of the Roman empire (IV ac century - under
Diocletian emperor).
4.2 Survey operations and instruments
A complete survey of the statue has been performed in order
to obtain the solid image of the sculpture. Some reflecting
targets (markers) has been placed on the object for the
automatic calibration process.
A Riegl LMS-Z420 laser scanner has been used for the
DDEM acquisition (see Fig. 5 a). This instrument has an
accuracy of ± 5 mm in the distance measurements. The
minimum angular step is 10 mgon.
The laser scanner acquisition of the statue has been earned
out from a mean distance of about 4 m and with angular steps
of 20 mgon. The time required for the scanning was about 20
minutes. The acquired point cloud has been filtered with a
specific software developed last year by the our research
group.
a)
Figure 5. Surveying of the Tetrarchi Statue, a) The Riegl
LMS-Z420 Laser Scanner
b) The obtained points cloud (DDEM).
