CIPA 2003 XIX th International Symposium, 30 September - 04 October, 2003, Antalya, Turkey 
iv) Light conditions are crucial for passive photogrammetric 
camera while active laser is independent from external 
lighting. 
v) Texture mapping with realistic colours over 3D model can 
be provided directly from photogrammetric picture. 
Nevertheless the lack of direct relation between images 
and object coordinates requires long process for 
producing 3D textured models. Laser scanner can provide 
black and white reflectance and realistic texture mapping 
can be provided with dedicates software. Few short range 
laser scanners can provide RGB information together with 
black and white reflectance. 
vi) Extraction of characteristic feature (i.e. edges, draw, and 
textural information) can be obtained through manual or 
semi-automatic tools within photogrammetric restitution 
process. This process is more difficult and generally less 
accurate for range scans. 
vii) Costs are higher for sophisticate laser instruments than 
for photogrammetric instruments. 
This no-exhaustive comparison between the two technologies 
reveals that none of them can solve all the problems inherent to 
architectural and archaeological survey. Laser scanner 
technology and photogrammetric techniques have a lot common 
points; a novel technique combining intensity and range data is 
presented for example in [Paulo et al, 2003], further 
developments are anyhow required to combine these two 
worlds. 
In this research work four major problems where using the 
synergy between the two technologies have been identified: 
1. Completing the model derived from laser measurements 
where data are missing through photogrammetric measures 
2. Increasing quality of the features (i.e. edges) extracted 
from laser scanner model through photogrammetric 
measures 
3. Increasing registration quality between laser range scans 
through photogrammetric measures 
4. Increasing calibration camera parameters for model 
texturing through photogrammetric measures 
This research focuses on the first and second problems. 
Moreover the 2 combined technologies provide measurement 
that involves the use of an expert system in order to rebuild an 
architectural or archaeological object. With the collaboration of 
architects or archaeologists is possible to derive ideal model 
from real measurements. 
In this paper the general methodological approach is presented 
in Section 2. Laser and photogrammetric tools adopted for 
testing are described respectively in Section 3 and 4. Details of 
the archeologically importance the case study we focused on, 
are detailed in Section 5. Survey, data processing and measuring 
object with a theoretical model are described in Section 6, 7, 
and 8. Combination of the different approach is faced in Section 
9. Case study result and final conclusion on the general 
approach are reported in Section 10 and 11 respectively. 
2. GENERAL METHODOLOGICAL APPROACH 
The work can be divided into 4 major steps: 
1. Laser scanner section 
2. Photogrammetric section 
3. Measuring object with a theoretical model 
4. Merging the different approaches 
Laser scanner section includes range scan acquisition and data 
processing through Reconstructor Software by Joint Research 
Centre nEuropean Commission n (JRC, EU). Single images are 
also acquired and combined with range data. A textured 3D 
model with lacks where laser data are missing (shadows and 
occlusions) is the out put results of this section. 
Photogrammetric section includes the acquisition of images pair 
with a proper base-line, camera calibration and programmatic 
model building. 
The photogrammetric process is divided in three steps from a 
very general one to a specific, artefact-dependent one, described 
in section 4. Geometric measurements derived from the 
combination of laser scanner and programmatic models are 
inserted in an expert system. Starting from real measurements, 
architectural and archaeological knowledge a theoretical model 
of the surveyed object can be derived.Laser scanner 3D model, 
photogrammetric model and theoretical model are merged and 
compare in a single tool. 
Figure 1 Method general scheme. 
3. LASER SCANNER TOOLS 
3.1 Laser scanner hardware 
Laser range finder (LFR) can determine the distance from the 
systemis observation point to all points of consideration in a 
scene. Many LFR systems for short and long range 
measurements are available on the market. 
LFRs can measure 3D pointis distances working with two 
different techniques: pulsed wave (time-of-flight) and 
continuous wave, [http://mortimer.jrc.it/] 
For this experimental job range data were acquired using 
Callidus LFR [http://www.callidus.de/]. 
Callidus measurements system is a time-of-flight LRF; a short 
laser pulse is emitted at a given frequency and the time elapsed 
between the emission and the received echo is measured. 
During the measuring process Callidus measuring head can 
turned: i) by 360oo along the horizontal plane (step size 
0.0625a? 0.125a? 0.25a? 0.5a? 1 .Oa), ii) by 180ooalong the vertical 
plane (step size: 0.25a? 0.5a?l ,0a). Range distance is given up to 
80 m (in radius). 
3.2 Laser scanner software 
Many software tools for range date processing are available on 
the market. Many of them has been traditionally developed for 
short range scan for reverse engineering purposes. Some laser 
scanner has property software which usually allows driving 
laser scanner acquisition and data storage.