High-resolution Underwater Robotic Vision-based Mapping and 3D Reconstruction for Archaeology
M. Johnson-Roberson · M. Bryson · A. Friedman · O. Pizarro · G. Troni · P. Ozog · J. Henderson
TL;DR
An AUV and a diver-held stereo rig produced a 26,600 m2, 2 mm/pixel 3D map of the submerged city of Pavlopetri.
BRIEF
Mapping a submerged archaeological site by traditional methods is slow, especially when it spans a large area. This work combines an autonomous underwater vehicle with a diver-controlled stereo camera platform to document the Bronze Age city of Pavlopetri, Greece. The result is a 3D reconstruction covering 26,600 m2 at 2 mm per pixel. Getting there required color correction across many images taken at different altitudes over different seabeds, bundle adjustment for upward of 400,000 stereo images, and a registration method for quickly mapping changes in excavation areas.
Abstract
Documenting underwater archaeological sites is an extremely challenging problem. Sites covering large areas are particularly daunting for traditional techniques. In this paper, we present a novel approach to this problem using both an autonomous underwater vehicle (AUV) and a diver-controlled stereo imaging platform to document the submerged Bronze Age city at Pavlopetri, Greece. The result is a three-dimensional (3D) reconstruction covering 26,600 m2 at a resolution of 2 mm/pixel, the largest-scale underwater optical 3D map, at such a resolution, in the world to date. We discuss the advances necessary to achieve this result, including i) an approach to color correct large numbers of images at varying altitudes and over varying bottom types; ii) a large-scale bundle adjustment framework that is capable of handling upward of 400,000 stereo images; and iii) a novel approach to the registration and rapid documentation of an underwater excavations area that can quickly produce maps of site change. We present visual and quantitative comparisons to the authors' previous underwater mapping approaches.