An Examination of Compression and Restoration Method of Measured Point Cloud Based on B-spline Surface Approximation of Flake Surfaces in Stone Implements

Abstract

Relics such as stone implements and earthenware are analyzed and researched archeologically according to point cloud data obtained by three-dimensional measurements of the relics. Relics are archeologically precious and some relics measured in this study are accompanied by a risk of damage caused by movement. In addition, a large quantity of relics are excavated from archaeological ruins. As such, it has a high cost to move the relics for measurement. Therefore it is effective to measure excavated relics locally and to transfer the measured data via an internet. However, as the measurement precision gets better it will result in a greater number of points which will increase the point cloud data size. Also, the long transmission times for these large-scale point cloud data becomes a problem. One of the methods to solve this problem is to use data compression to express point clouds with smaller amount of data. This study examines the method to compress point cloud data by approximating flake surfaces in stone implements with trimmed surfaces, which can be expressed with the smaller number of control points than the total number of points in a point cloud. In addition, this study examines the method to restore a point cloud data from the trimmed surfaces. We applied this method to a point cloud data measuring in a 0.1mm pitch and a good result was obtained.