In our research, that will end in December 2015, we are going to explore the potential of this system.
From the theoretical point of view the geometry of the epipolar lines in the whole image of the spherical panorama has been
just analysed and the correctness of the algorithm has been assessed Fangi, Nardinocchi, 2013. for this reason now you
have to work on procedure to make automatic the restitution process. Spherical Photogrammetry, PSP, pipeline is based on
recent advances in automatic restitution processes. PSP could be a very good system for cultural heritage metric
documentation especially when we have to document many sites, it is the case of G-Bay, a database in which we have to put
information on more than 800 churches of Naples. The main advantages of this method are the speed of the survey, the low
cost of the equipment and the completeness of the acquired information, but the orientation and restitution procedures are
still fully manual Fangi, Nardinocchi, 2013. We can generate panoramic images in different way but we can
use these images for measurement only when they are made by using a tripod and a spherical head expressly designed for
panoramic imaging, allowing the coincidence of the centre of views of the images. Using some of the most popular stitching
software we can compensate both for radial distortion and for residual horizontal and vertical shift offsets and produce a
panoramic image that can be used for a 3D restitution. Actually the method is based on classical photogrammetry
principles: orientation of multiple panoramas and manual 3D object reconstruction.
Until automated PSP processing becomes available recent experimentation in the manual restitution are generally based on
the use of Image Based Modeler software, such us Autodesk Image Modeler, that allow directly produce 3D model from
oriented photos and panoramas. Calibration, modeling, and texturing are the three-steps of this system but there are some
problems in modeling tools, thus sometimes we need to use other 3D model software Cannella, 2013. To calibrate the
equirectangular panoramas you need 6 points well recognized in the images, its better more than 6, and to get more accurate
3D model you should also use some known geometrical features or, if its possible, the coordinates of some points. The
expertise of the operator is very important to produce an accurate 3D model based on the homologous points search, as a
matter of fact that image matching may generate a very great errors as well as an incorrect reading of the geometries.
In our researches we are going to produce 3D model of San Lorenzo Maggiore in Naples from 360° panoramas using Image
Modeler. The comparison between 3D data from laser scanner survey will allow us to assess different geometric accuracies
coming from different sources of information, also in relation to processing time to produce 3D model.
We are also testing this method in the research about Gothic French cathedrals. In this case we are interesting in the study of
geometric configuration of the vaults and we think that the accuracies of the 3D model produced it could be good for our
aims and errors in measurement are within acceptable tolerances required by research in progress.
2.2 The use of 360° panoramic image as interface to 3D
data
In recent years the advances in laser scanner technologies has allowed fusion of digital panoramic camera data with laser
scanner data, this has strongly contributed to widespread use of 360° panoramic images. We have used a FARO Focus 3d Laser
Scanner for our survey, that allows to export each individual scan as a panoramic image.
The spherical images from laser scanner could be also adopted to share easily 3D data on simple browsers platform. SCENE
WebShare Cloud, FARO, offers a comprehensive service package to provide users with simple access to 3D
documentation. The structure for WebShare is produced through automated software and can be readily made available
on an intranet or internet via Webshare Server which is free. This enables a publishing project and multi-user browser using
panoramic images one for each scan with simultaneous display of position and orientation in plan.
Figure 5 . Naples S. Lorenzo Maggiore. SCENE WebShare: using this system 360° immersive images could be considered a
user interface to access 3D data.
Figure 6 . Naples S. Lorenzo Maggiore. Survey data from SCENE WebShare Cloud.
ISPRS Technical Commission V Symposium, 23 – 25 June 2014, Riva del Garda, Italy
This contribution has been peer-reviewed. doi:10.5194isprsarchives-XL-5-137-2014
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Figure 7. S. Lorenzo. Comparison betweens model from 3D laser scanner point cloud and theoretical model.
These arent simple panoramas because they are produced by 3D dimensional scan, for this reason, using this system, its
possible conducting measurements directly on the panoramic images Figures 5, 6.
We are going to use the WebShare structure in our database, in this way, 360° panoramas produced from laser scanner could be
considered a user friendly interfaces to interact with 3D data. In some cases this system could be very useful for scholars, that
need to measure in order to verify their hypotheses. In our research about Gothic cathedrals we have used this
method to study the geometric configuration of Church of San Lorenzo Maggiore in Naples.
Our target is to understand the transformation of gothic features from French to Naples. To study the geometric vaults
system, we have produced three models: one theoretical model based on the study of treatises, one surveying data from
SCENE WebShare Cloud and the last one using data from laser scanner survey Figures 7, 8. In this way we are able to test the
different geometric accuracies coming from different sources of information and to verify our critical hypotheses. In fact, from
the study of Viollet-le-Duc and Villard de Honnecourt Figure 8 . Naples S. Lorenzo Maggiore. Gothic vaults geometry
from laser scanner data.
Figure 9. S. Lorenzo, Geometry from laser scanner point cloud. we can produce a 3D model based on the application of some
rules, for example the three arcs rule of Villard, and then we can check if these rules have been followed or not Figure 7.
If you consider the gothic trapezoidal vaults in S. Lorenzo ambulatory, you can built a model according to treatises. You
can produce some different models, for example you can assume that diagonal ribs AC and BD are semicircular arches
and the AD, BC and DB are pointed arches with the same radius of curvature of diagonal arches. In this way we can
verify producing 3D model based on these hypotheses that the keystones of the arches are at different heights Figure 10.
To understand what kind of rules has been used in S. Lorenzo, we have crossed the point cloud to verify the arches nature and
we have surveyed that the diagonal arches AC and BD arent semicircular arches but they are two centers arches, while AB
is a semicircular arches and AD, BC and DC are pointed arches with same radius of AB Figure 11.
ISPRS Technical Commission V Symposium, 23 – 25 June 2014, Riva del Garda, Italy
This contribution has been peer-reviewed. doi:10.5194isprsarchives-XL-5-137-2014
140
Figure 10. S. Lorenzo, 3D Geometry model from theoretical hypotheses
The comparison between 3D model from laser scanner and 3D model from WebShare allows us to value two different manual
methods 3D model production, while the comparison with the theoretical model allows us to deepen knowledge of the cultural
heritage. As a matter of fact that, survey isnt only a metric documentation method but it is a critical analysis tool.
3. 3D PDF: AN INTERFACE TO ACCESS 3D DATA
