A CASE STUDY FOR THE PRACTICAL USE OF 3D DIGITAL ARCHIVE OF
CULTURAL PROPERTIES
Osamu Yamada”, Yutaka Takase*
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? CAD CENTER CORPORATION, 23-2 Sakamachi, Shinjuku-ku, Tokyo 160-0002, Japan
(o-yamada, takase)@cadcenter.co.jp
PRitsumeikan University, 56-1 Tojiin-kita-machi, Kita-ku, Kyoto 603-8577, Japan
Commission V, WG V/4
KEY WORDS: Laser Scanning, Visualization, Computer Graphics, Cultural Heritage, Point Cloud
ABSTRACT:
A scanning device generally referred to as a "laser scanner", used to obtain 3D data of objects by irradiating laser beams, is used in
the field of cultural properties, and is starting to achieve significant results. The technique to record complex 3D data with high
accuracy and speed, without touching or destructing an object, makes it an essential tool in the field of cultural properties, as well as
arousing interest in the displaying of such data on a computer, and in the various possible usage of the obtained 3D images.
The authors have implemented this laser scanning technique to obtain data for such various fields as architecture, fine arts,
monuments, and historic sites, with good results. This paper is written to consider application of this technique for efficient
conservation of cultural properties, referring to the 3D laser scanning activities performed by authors up to the present.
The 3D digital archive making with laser scanner requires two steps, which are actual measurement works and digital processing of
the data acquired. The acquired point clouds in three dimensions can be displayed on a computer by using the exclusive software and
we have to process (align, merge and so on) these data considering subsequent works also.
Up to the present, the authors have performed many practical applications using 3D digital archives of cultural properties measured
by laser scanner. These are valuable records for various purposes: handing over to future generations, creating 2D information,
investigating inclinations, preparing basic data for examination of a restoration plan, visualizing CG animations and others.
In this paper, the authors wish to introduce the method of measurement using laser scanner, and the subsequent processing of the
obtained data, in order to clarify the validity and possibility of application for creating efficient and valuable digital archives.
1. INTRODUCTION
Cultural heritage is a memory of human history and footprints
in the sands of time, giving a glimpse of humankind's way of
life, technology, and wisdom that emerged and dominated
various periods of time in which they were made. They are
vulnerable to natural wear and tear, not to mention damage
caused by disasters. In fact, we have been constantly losing
cultural heritage, whether we know it or not.
At the same time, we have been striving to preserve them in
their original state or condition, as much as possible, in order to
bestow them onto the next generation. Our 3D laser scanning
technology is one way to archive this objective.
Although laser-scanning technology can be applied for a wide
variety of areas, in this paper, the method of actual laser
scanning, processing point cloud data, and the practical use of
data will be explained, with some practical examples.
2. PROCESS OF 3D DIGITAL ARCHIVES
2.1 The Laser Scanner
Various types of laser scanners have been developed, and the
principle of measurement, accuracy, speed, density, range, and
price are different for every type of laser scanner. In laser
scanning, it is important to choose the optimal scanner
depending on the object to bc measured and the purpose of
measurement. In recent years, research on performance
comparison of these laser scanners, including the accuracy of
point cloud data obtained, have been performed.
As for typical principle of the measurement, there are two kinds,
"time of flight" and "triangulation".
The authors possess both types of laser scanners, VIVID900
(Fig.l) and Cyrax2500 (Fig.2), and use whichever more
appropriate, considering the object and the purpose of
measurement. Generally speaking, VIVID900 is used for
smaller objects up to several meters in width, and Cyrax2500 is
used for larger objects. The specifications of the scanners are as
follows (Table I).
VIVID900 Cyrax2500
Principle Triangulation Time of flight
Laser class Class2 Class2
Range 0.6-2.5m 1.5-50m, up to 100m
Accuracy 0.2-1.4mm 6mm(@50m
Speed 640x480points/2.5sec. 1000 points/sec
Dimension D 27IxW213xH413mm 400x330x430mm
Weight 11kg 20.5kg
Table 1. Specifications of the Two Scanners
There exist cases where obtaining of data becomes a difficulty.
For example, when the color of a surface of an object is black,
laser beam is absorbed; glass, water, and related materials
penetrate laser; and mirrors reflect laser beams in a special non-
desirable way.
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