14 Underwater Multimodal Survey: Merging Optical and Acoustic Data
231
This particularity is a essential to create a model of complex structures like walls,
caves, overhangs . . .
The BlueView BV5000 system used is composed of a high frequency sonar (1,35
MHz), mounted on a pan & tilt system. Both Sonar and pan & tilt are managed from
the surface by the dedicated software.
The system works by mechanically scanning a thin vertical sonar slice around the
selected area. At each direction, a profile of the surface is taken and added to the
other direction profiles to create a final 3D point cloud.
Through mechanical rotation of the sonar head, the BV5000 is capable of
producing 3D points from a stationary location
To cover all the structure with enough density of points, multiple stations can be
realized around the site and merged after by algorithms like ICP (iterative closest
points).
Some reference points can be located with high accuracy in absolute coordinate
system to georeferenced the final model.
The sonar head is composed of 256 beams for an aperture of 45
◦ . The beam width
is 1
◦ per 1
◦ and time resolution is 3 cm. The maximum range is 30 m to be optimal
between 1 and 20 m.
14.4 Experimentations
We present here the first experimentations of the ROV-3D project. The first one is
merging acoustic data with photogrammetry in a cave close to Marseille (Fig. 14.7).
And the second one is a survey of a modern wreck, “le Liban” also close to Marseille. This second survey is done only with photogrammetry with more than 1,00
photographs.
14.4.1 Close Range Acoustic and Optical Survey
Under the ROV-3D project we experimented with the fusion of acoustic data from
two sensors, high precision, high frequency acoustic camera sold by Blue View
and the photogrammetry system automatically MENCI society (see Fig. 14.5). An
experiment was done on the Cave of the Imperial land in Marseilles.
The 3D Scanner is a BlueView BV5000 of active acoustic system that provides
a point cloud of 3D high-resolution imagery of underwater sites, see the scanner
during the acquisition phase in Fig. 14.6.
Unlike conventional bathymetric measurement systems that retain only the high
points, the 3D sonar, installed near the bottom, can acquire and maintain multiple
points of elevation Z for a given pair of coordinates (X, Y).
This system “3D Scanner” opens up new possibilities for constructing 3D models
of complex structures such as drop offs, overhangs, or even caves.
The “3D scanner” is mounted on a hinged support along 2 axes (horizontal and
vertical) allowing rotation from top to bottom and from right to left.
231
This particularity is a essential to create a model of complex structures like walls,
caves, overhangs . . .
The BlueView BV5000 system used is composed of a high frequency sonar (1,35
MHz), mounted on a pan & tilt system. Both Sonar and pan & tilt are managed from
the surface by the dedicated software.
The system works by mechanically scanning a thin vertical sonar slice around the
selected area. At each direction, a profile of the surface is taken and added to the
other direction profiles to create a final 3D point cloud.
Through mechanical rotation of the sonar head, the BV5000 is capable of
producing 3D points from a stationary location
To cover all the structure with enough density of points, multiple stations can be
realized around the site and merged after by algorithms like ICP (iterative closest
points).
Some reference points can be located with high accuracy in absolute coordinate
system to georeferenced the final model.
The sonar head is composed of 256 beams for an aperture of 45
◦ . The beam width
is 1
◦ per 1
◦ and time resolution is 3 cm. The maximum range is 30 m to be optimal
between 1 and 20 m.
14.4 Experimentations
We present here the first experimentations of the ROV-3D project. The first one is
merging acoustic data with photogrammetry in a cave close to Marseille (Fig. 14.7).
And the second one is a survey of a modern wreck, “le Liban” also close to Marseille. This second survey is done only with photogrammetry with more than 1,00
photographs.
14.4.1 Close Range Acoustic and Optical Survey
Under the ROV-3D project we experimented with the fusion of acoustic data from
two sensors, high precision, high frequency acoustic camera sold by Blue View
and the photogrammetry system automatically MENCI society (see Fig. 14.5). An
experiment was done on the Cave of the Imperial land in Marseilles.
The 3D Scanner is a BlueView BV5000 of active acoustic system that provides
a point cloud of 3D high-resolution imagery of underwater sites, see the scanner
during the acquisition phase in Fig. 14.6.
Unlike conventional bathymetric measurement systems that retain only the high
points, the 3D sonar, installed near the bottom, can acquire and maintain multiple
points of elevation Z for a given pair of coordinates (X, Y).
This system “3D Scanner” opens up new possibilities for constructing 3D models
of complex structures such as drop offs, overhangs, or even caves.
The “3D scanner” is mounted on a hinged support along 2 axes (horizontal and
vertical) allowing rotation from top to bottom and from right to left.