# Positioning Systems for Unmanned Underwater Vehicles: A Comprehensive Review
## 3 Reviewing Positioning Systems and Their Capabilities
### Improving the Categorization  
In Section 3.3, we created Table 1 to categorize positioning systems based on several key factors: horizontal range, overall cost, suitability for deep waters, maintenance costs, and the type of vehicle they are used for (AUV or ROV). The table starts with references, which are crucial for understanding the positioning technologies discussed in each source. Identifying the positioning technology used or mentioned in each paper is essential for improving the categorization in Table 1. As mentioned in Section 1, Unmanned Underwater Vehicles fall into two categories, as shown in Table 2[15]. During our categorization process, we noted that some papers indicated that \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Reference** & **Positioning System** & **Advantages** & **Disadvantages** \\ \hline
[15; 44; 46; 100; 101; 102] & Inertial Navigation & -No need for external signals & -Drift over time leading to \\  & System (INS) & -Can operate in GPS-denied environments & decreased accuracy -Reu gives periodic calibration \\ \hline
[47; 103] & Long Baseline (LBL) & -High positional accuracy & -Reu requires installation of \\  & & -Effective in deep water & multiple transponders \\  & & -Suitable for complex environments & -Limited mobility during setup \\ \hline
[50; 51; 103] & Short Baseline (SBL) & -Less complex than LBL & -Lower accuracy compared to LBL -Limited range and precision \\  & & -Suitable for shallower waters & -Lower accuracy compared to LBL -Limited range and precision \\ \hline
[51; 104; 105; 106] & Ultra-Short Baseline (USBL) & -Real-time tracking & -Less accurate at greater distances -Requires only a single transducer -Performance can be affected by -Good for dynamic environments & -Less accurate at greater distances \\ \hline
[52; 53] & Doppler Velocity Log (DVL) & -Provides velocity relative to the seafloor & -Performance can be affected by water \\  & & -Enhances positioning accuracy when & conditions and seafloor characteristics -Not a standalone positioning system \\ \hline
[4; 54; 55; 56] & Dead Reckoning & -Simple and cost-effective & -Accuracy degrades over time -Dependent on accurate \\  & & -Useful for estimating position in the & -Dependent on accurate \\  & & absence of other data & initial conditions \\ \hline
[57; 58; 59] & Acoustic Modem Systems & -Enables communication between UUVs and surface vessels & -Limited bandwidth -Communication can be affected by \\  & & -Can assist in positioning and data transfer & water conditions and distance \\ \hline
[15; 75; 107; 108; 109] & LIDAR (Light Detection and Ranging) & -Provides high-resolution 3D data & -Limited depth penetration -Requires clear water conditions \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Advantages and disadvantages of different technologies. certain positioning systems could be used for both Autonomous Underwater Vehicles and remotely operated underwater vehicles. Additionally, part of our research [39] involved hybrid underwater vehicles, and we also encountered autonomous underwater gliders [16].