Augmented Diving service is intended for the divers who are going to visit the underwater site, allowing them to have a virtual guide that provides specific information about the artifacts and the area they are visiting. The service is based on a tablet properly equipped with a waterproof case and an integrated system for acoustic localization and inertial navigation.
The underwater positioning tools currently available on the market are based on very expensive acoustic communication systems, which estimate the position of the receiver by computing the distance from at least three fixed transmitters (LBL - Long Baseline) or use a single transmitter and an array of receivers (SBL / USB - Short / Ultrashort Baseline).
The goal of the VISAS project is to build a low-cost underwater positioning and orientation system composed by one or more fixed beacons placed on the seabed and an underwater tablet equipped with an acoustic modem (LBL technique, see Figure 4). In order to improve the accuracy and increase the robustness in case of loss of signal from one or more beacons, the tablet is also equipped with an inertial platform and a depth sensor. The data coming from the various sensors are processed through data fusion and error estimation algorithms.
The tracking system on the tablet sends a query to the beacons and computes the distance from each of them. These data are used by the data fusion algorithm to correct the estimate on the position obtained through the inertial system and the pressure sensor. The navigation software receives this information and shows the location of the tablet on a 3D map of the underwater archaeological site.
The user interface of the augmented navigation system guides the diver along the selected track inside the archeological site. Using the tablet position and orientation, the app shows a 3D map representing the environment around the diver, adding useful information about underwater artifacts and structures. Moreover, some additional data are displayed: system status, battery charge, water temperature, and depth. The diver can also change the view mode or open the camera device to shoot a photo. The photos are automatically geo-referenced.
Figure 4: VISAS Augmented diving system