# Deepwater 3D Measurements with a Novel Sensor System
## 3 Results
### Offshore Measurement Examples  
To evaluate both 3D sensor systems, various experiments were carried out in an application-related environment in the Baltic Sea. These experiments were carried out in collaboration with the company BalticTaucher [37]. The calibration of the two sensor systems was accomplished on-site according to the method described in Section 2.2. For the experimental measurements, the sensor systems were mounted on a work-class ROV and controlled from a ship (see Figure 6).  
As part of the experiments regarding use case 1, various measurement objects were placed in a row on the seabed, and the entire scene was reconstructed. Scanner speeds  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Distance (m)** & **Error S1 (mm)** & **Noise (mm)** & **Error S2 (mm)** & **Noise (mm)** \\ \hline
1.5 \(\pm\) 0.01 & 0.21 \(\pm\) 0.07 & 0.07 \(\pm\) 0.01 & 0.04 \(\pm\) 0.01 & 0.07 \(\pm\) 0.01 \\ \hline
1.8 \(\pm\) 0.01 & 0.18 \(\pm\) 0.01 & 0.09 \(\pm\) 0.01 & 0.02 \(\pm\) 0.03 & 0.08 \(\pm\) 0.01 \\ \hline
2.1 \(\pm\) 0.01 & 0.33 \(\pm\) 0.01 & 0.09 \(\pm\) 0.01 & 0.05 \(\pm\) 0.06 & 0.09 \(\pm\) 0.01 \\ \hline
2.4 \(\pm\) 0.01 & 0.37 \(\pm\) 0.04 & 0.13 \(\pm\) 0.01 & 0.12 \(\pm\) 0.04 & 0.10 \(\pm\) 0.01 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Sphere radius error, depending on the measurement distance in water basin. The calibrated radii of spheres S1 and S2 are 50.202 mm and 50.193 mm, respectively.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Distance (m)** & **Flatness Deviation (mm)** & **Noise (mm)** & \(n\) \\ \hline
1.7 & 0.33 \(\pm\) 0.04 & 0.06 \(\pm\) 0.01 & 4 \\ \hline
2.0 & 0.37 \(\pm\) 0.04 & 0.07 \(\pm\) 0.01 & 4 \\ \hline
2.4 & 0.73 \(\pm\) 0.13 & 0.15 \(\pm\) 0.02 & 4 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Distance-dependent flatness deviation and noise of sensor UWS1 on the normal plane in water basin.  
between 0.2 m/s and 0.5 m/s were achieved. The manual control of the scanner system by the ROV pilot could not achieve a constant speed.  
An example of the reconstruction result of many measurement objects, including clay pots, normal planes, ball-bars, dummy bombs, and cylinders on the seabed, is shown in Figure 8.  
As part of the experiments regarding use case 2, a pipe segment was reconstructed. This experiment was carried out both in the water basin and offshore. The pipe segment was placed on the bottom of the water basin or on the seabed. The test in the water basin was carried out by connecting the sensor system to a controllable traversing unit with which exact speeds could be achieved. A scanner speed of 0.7 m/s was achieved. As a result, the part of the pipe segment visible from above could be completely reconstructed (see Figure 9). When measuring offshore pipes, ball-bars were placed next to the pipe sections to determine the dimensions (see Figure 9).  
Additionally, individual objects in the test row were reconstructed separately. This applies to reference measuring bodies, various clay pots, and a dummy bomb. Underwater 3D reconstruction results of one of the clay pots and the dummy bomb are documented in Figures 10 and 11.  
Figure 8: Reconstruction result of line of test objects using visual odometry and color mapping.  
Figure 9: Reconstruction results of a pipe section: measurement in the water basin, reconstruction result water basin, pipe for underwater measurement in air (**from left to right above**), and underwater reconstruction result for offshore measurement (**below**).  
The high accuracy potential of the 3D sensor can be seen in the detailed reconstruction of the damage (long notches and grooves) on the dummy bomb. These are not measurement artifacts but are actually present on the object's surface.