Evaluation of a high-end laserscanner for underwater archeology

Archeology has been provided with many new technologies over the last years, like magnetometers, Lidar, etc. This resulted in new discoveries that would have not been possible without these new techniques.Underwater archeology has also made progress in utilizing new technologies like special sonars, high resolution cameras, magnetometers or sub-bottom profilers. A very interesting device for this application is a laser scanner which is almost common for on-land scanning but much more challenging for using under water.Laser scanners can provide a very accurate (sub-millimeter accuracy) model of a submerged object. In order to gather such data a stable platform for the sensor is needed. Stabilizing the platform under water is a very challenging task because of currents or other environmental parameters.This paper describes the integration of the high-end laser scanner SeaVision from Kraken Robotik (KRG, Bremen, Germany) into an inspection class ROV for their application in underwater archeology. While the mechanical and electrical integrating could be done without problems, integrating the software and graphical user interfaces into one GUI was more challenging. But the result was an intuitive system that could be operated from two persons aboard a survey ship and made scanning of objects very easy.The State Office for Monument Conservation and Archeology in Saxony-Anhalt (LDA) has always been interested in using new technologies for exploration. Starting in 2017 the first trials of underwater archeology were made and until now more than 20 missions in several lakes were successfully finished.In 2018 a new target for exploration was identified – the Arendsee in the north of Saxony-Anhalt. This lake has long history and was first mentioned around 800 A.D. because of a huge collapse sinkhole near the lake. After the collapse, the lake size doubled and it is expected that many interesting artefacts were preserved this way at the bottom of the lake.An exploration with an AUV in 2019 and the resulting sidescan images clearly showed interesting objects on the floor and their evaluation and documentation should be done in a separate trial with a ROV equipped with a laser scanner in late 2020.The mission was successfully finished with partners from KRG, LDA, German Red Cross Water Rescue (Halle/Saale) and Fraunhofer IOSB-AST (Ilmenau, Germany) in October 2020.In this paper, the technology used for this trial will be described – especially the laser scanner and the inspection ROV. Furthermore, a short historical overview about the lake and why it is so interesting for German history will be given and what artefacts were expected.The results of the survey including images from the trial, underwater images of objects and laser scanner models will be showed with the explanation from the specialists of the archeology office in Halle. The paper concludes future missions that are already planned with this vehicle setup as well as the possibilities to use the laser scanner in other vehicles for different applications like inspection or maintenance.