UWIS dive: Photogrammetry
UWIS participated in a wreck photogrammetry dive trip on the Baltic Sea, Finland
Mission: UWIS was invited to be involved in carrying out the 3D modeling work requested by the Åland's Maritime Museum on a wreck found but not yet identified.
At the same time, we investigated how the position information provided by UWIS helps in photogrammetry.
Watch video from here:
UWIS Photogrammetry
This so-called "the wreck of Signilskär" has been known for a long time, but its breakdown and the size of the wreck area make it difficult to identify. The diver does not see the whole area with a typical visibilty of about 6 meters.
For this reason, a 3D model implemented using photogrammetry can help researchers to identify the wreck.
Attached is a side scan sonar image of the wreck.
The water temperature was about 4 degrees, visibility in the water about 6 meters and maximum depth about 16m.
The four-day dive trip was organized by the local wreck diving club "Nautic Club Urheilusukeltajat ry.", whose Tavi ship is very capable of this kind of trips. A total of four wrecks were dived on the same trip, of which this wreck located north of Signilskär island was the only unidetified wreck.
Below are photos of the ship itself on the way.
We mounted one UWIS diver unit on the back of the cameraman, allowing us to record his motion every two seconds.
During the two and a half hours of recording time, two pairs of divers carried out by three dive times.
Prior to imaging dives, markers for photogrammetry were introduced at critical points on the wreck. Later those were collected from the wreck. All divers on the ship took part in the dives and with good teamwork we were ready after the morning.
During the dives, Tavi's computer monitored the progress of the dives. We have installed an external antenna on the board to reinforce the UWIS system's wifi network. This allows us to be almost 1km from the buoys while watching the dive. This time the distance was only some 60m.
At the same time there was three views on the screen: Side scan sonar pircture, previous dive routes and a real-time dive image of UWIS Tracker. These views ensured that the most important parts of the wreck were filmed.
Below are pictures of the wreck as they were depicted on the model. Two images per second were captured from the video resulting in a total of 9000 images.
Due to the size and quality of the wreck field together with poor visibility, such a number of images would probably have been mission impossible for a modeling program without the location information provided by UWIS for each image.
On the way home, we combined the location data with the images, and after the trip, the club's 3D modeling experts first used Agisoft's Metashape software to combine the images into a mesh model and then into a 3D model with surface textures.
The 2D (ortho) image taken from the model can be used as an overlay for underwater navigation.
The images below first show the Excel page that was used to complete the location data. The second picture shows the position data read by Metashape and the last picture shows the dive routes on top of the orthoimage.
Excel data (CSV)
Metashape positions
orhoimage & dive tracks
The result was a gorgeous 3D model with an orthoimage below.
This technique can be used e.g. in marine archeology and biology as long as the subject does not move during shooting.
UWIS enables large areas to be modeled with low cost hardware.
