International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XL-5/W2, 2013 
XXIV International CIPA Symposium, 2 — 6 September 2013, Strasbourg, France 
2.TYPOLOGY LEADING TO PROTOCOLS 
However, we can classify the corpus of artefacts in groups 
sharing similar constraints. This organisation of the corpus in 
typologies leads to different protocols developed as guidelines. 
2.1General explanations 
Managing the acquisition requires to understand the basic 
concepts of the data processing. 
Understanding the basic concepts of data processing is a 
necessary first step towards the understanding of the protocols. 
Therefore, a first document explains the different steps of the 
Culture 3D Clouds pipeline (tie points computation, internal 
orientation, external orientation,dense image-matching, points 
clouds generation and meshing) and the constraints previously 
delineated. 
For these explanations, we need a vocabulary both rigorous and 
easy to understand for the non-experts. This is why technical 
photogrammetric vocabulary will be used as little as possible or 
will be simplified. However, some vocabulary are necessary 
such as 'orthoimage' which will require clear definitions. 
Although the visual standard of representing a camera by a 
pyramid is used in our protocols (see Figure 2). 
Moreover, our Protocols uses the standard of representing a 
camera as a pyramid (see Figure 2). 
This way, it is still possible to show different focal lengths and 
the photographers are then able to read photogrammetric 
explanations from other sources. 
Aware of these specificities, the photographer is able to 
understand where the difficulties lie. We can list three essential 
rules which must be controlled as much as possible: 
* The photographs must be automatically orientable. 
* Each master photograph and the related associated 
photographs must be suitable for the dense 
image-matching: sharp, in sufficient number for 
multi-stereo, with a good height-base ratio and 
representing the whole surface with a precise texture. 
* The colours must be well reproduced and permit 
radiometric equalization. 
These rules impose conditions on different parameters. Some 
are listed in the tables 1 and 2. 
  
Automatical Quality Good Fepro: 
; ; dense image- | duction of the 
orientation ; 
matching colors 
hort imal 
focal length(s) 3 Mer o 
necessary magnification 
focus small change | fixed 
; depth of field | used for the 
aperture fixed : e 
maximal characterization 
enough for ; ; 
sharpness : : maximal maximal 
tie points 
no flare no flare, sha- 
hat all over the | visible texture dow or reflect 
lighting ; 
artefact no shadow characterized 
no reflect (colorimetry) 
texture for smooth 
os no no 
projection surface 
overlapping almost 100 % 
7 See Table 2 — 
rotation angle 10° 
Table 1: Some parameters relative to the constraints 
Overlapping Rotation Proportion of 
of textured | of the artefact 
background camera | necessary in 
necessary (ratio of | the frame 
lap) 
Mainly artefact 
: ; 1/5 1/36 4/5 
used for orientation 
Both artefact and 
background used V 1/16 % 
for orientation 
Mainly background 
used for orientation 4/5 1/8 0 
Table 2. recommended parameters for automatic orientation 
These parametrizations are not absolute but constitute an entry 
point. 
For instance, to take intermediary pictures automatically 
orientable, the photographer has to understand the different 
parameters and the links between them. The rotation angle of 
the cameras (giving the required number of pictures) is linked 
with the overlapping of the background and its texture. For 
example, only height intermediary pictures can be sufficient if 
they are taken from a high-angle shot framing on a textured 
support. 
Nonetheless, the settling of the acquisition depends on the 
artefact. We need to provide the correct protocol for the 
photographer. 
2.2 Typological approach for protocols 
To do this, how do we split up the complete architectural and 
museum corpus? 
The user of the pipeline needs to focus on the sensitive 
technical constraints. The physical characteristics of the artefact 
are the base of the typological approach : 
* morphology (convex, concave or flatten), 
* scale, 
* texture (sharp all over the surface or smooth), 
* brightness. 
SCALE 
  
  
AA 
An 
Nn 
"n 
  
   
  
  
"MORPHOLOGY 
Figure 1. One of the typologies 
With the typology presented in figure 1, the user can rapidly 
understand the different general cases to which corresponds 
protocols with a spatial configuration of acquisition. 
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