Gribshunden sank at year 1495. The Danish warship of King Hans which on that fateful day caught fire while at anchor in the shelter of an island named Stora Ekön.
Now, more than 500 years later, a multinational research team is cleaning up some of the wreck with the aim of finding more interesting details and hoping those are enought for the expanded project for the dedicated museum.
UWIS came in at a stage when the wreck had already been made a three divemensional and hand-dawn drawing.
The water was warm at about 18 degrees of Celsius, visibility in the water about 6 meters and maximum depth about 10m.
The dive data and communication generated by UWIS can be utilized by the "Valtamer Navigator for UWIS" program implemented on the Alltab underwater tablet. To this program can be installed a geo-referenced image in the background (overlay), allowing the diver to navigate visually over the image. The illustrations below show three different overlays on the program sceen before diving. The first image is a hand drawn wreck image, the second is a sonar image and the last image is a photogrammetric orthoimage.
The diver can seet not only his own position and direction, but also other divers' locations, marked destinations and incoming messages. The diver can also mark new targets and send messages to the surface and to other divers.
Overlay: 3D model orthoimage
Alltab is an underwater tablet that is designed to work up to a depth of 150m. It is also the dimensioning depth of UWIS diver units.
The diver can either hold the tablet in his hand or attach it to, for example, an underwater scooter. The bottom line is that the UWIS diver unit "sees" the UWIS buoy units on the surface for spatial information and communication.
UWIS diver unit is usually attached to the diver's back when its postion is tracked only on the surface and does not itself use an undewater display device.
At Gribshunden, they tracked three divers simultaneusly.
UWIS devices and PCs with UWIS Tracker software collect dive-related log files. This information can be saved in KML, GeoJSON or NMEA format and used for post-reporting.
The screenshots under (Google Earth Pro) show the first two days' dive routes on a map with geo-referenced layers added.
Divers went to mark interesting sites and then they dived along the security lines around the wreck. With these dives, the UWIS geo-location and overlay picture locations threw about three meters, which still goes to normal GPS postitioning accuracy. Nor did we know, if the overlay picture was in place.