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INVESTIGATING SEVERAL POINT CLOUD REGISTRATION MOTHEDS
Luo Dean 1 , Zhou Keqin 1 , Huang Jizhong 2
1 Dept, of Surveying and Mapping, Beijing University of Civil Engineering and Architecture, No.l Zhanlanguan Road,
Xicheng District, Beijing, PRC - (Luodean, Zhoukeqin)@bucea.edu.cn
2 Yungang Grottoes Research institute, Yungang town, Shanxi Datong, PRC-Zhjizhong@yahoo.com.cn
KEY WORDS: 3D Point Cloud, Registration, Accuracy, Terrestrial Laser Scanner
ABSTRACT:
Terrestrial laser scanner (TLS) technology is widely used for 3D reconstruction and modelling in the field of heritage recording. For
any object of complex geometry, multiple scans are typically required to generate a 3D model. In order to get a whole 3D model, it’s
necessary to transform the scan data from the sensor's local coordinate system into a uniform Cartesian reference datum, and the core
task is point cloud registration. Today, various ways are available to register point clouds to each other, they are: ©Populating a
survey network with scans,© Direct merging of scans with each other,© “Cloud-to-cloud” registration, and have different
characteristics and different work styles. Based on the point clouds captured for YUNGANG Grottoes, the above three registration
methods are employed to merge multiple scans into a uniform reference datum. Three different registration procedures, data
matching accuracy, and test results are described in details. By comparing and analysing to the three registration results, the most
suitable way is found to meet our work.
1. INTRODUCTION
Terrestrial laser scanners (TLSs) have found application to
many measurement tasks, particularly for cultural heritage
recording. Their high resolution, accurate and rapid point cloud
capture capabilities allow cost effective production of digital
documentation of cultural heritage features. In fact, this
technology may entail any task from the digital preservation of
historic and culturally significant structures to mapping
archaeological dig sites. Laser scanning for cultural heritage
recording is increasing in popularity. There are numerous
scoping papers in which authors discuss the potential of TLS
for cultural heritage recording and report research findings
(Boehler et al. 2002; Bomaz et al. 2003; El-Hakim et al. 200).
For any cultural heritage recording project, field data captured
work is easy to be done by TLS, but a series of laborious works
have to be done one by one in order to get the object 3D
models. In most cases, single scan is not enough to reconstruct
the object 3D model, the object has to be scanned from
different viewpoints in order to completely reconstruct its 3D
model. Because each scan has its own local coordinate system,
all the local point clouds must be transformed into a common
coordinate system. This procedure is usually referred as
registration. The registration of point clouds is an essential task
in TLS applications.
Based on the point clouds captured for YUNGANG Grottoes,
three registration methods are employed to merge multiple
scans into a uniform reference datum. Three different
registration procedures, data matching accuracy, and test
results are described in details. By comparing and analysing to
the three registration results, the most suitable way is found to
meet our work.
This paper introduces our research background firstly. Section
2 briefly lists the main registration methods, and discusses their
merits and demerits. Section 3 describes three different
registration procedures for the point clouds captured for
YUNGANG Grottoes. Section 4 comparing the three
registration results in details, and the most suitable way is
found to meet our work. Finally, Section 5 gives the
conclusions and some proposals for the same works.
2. BACKGROUND
Yungang Grottoes is the model of the culture’s compromising
between China and Western and the spirit of the eastern stone
carving art. It is located in Yungang town 16km from Datong,
and was firstly carved 1500 years ago (in A.D. 460). The
Yungang Grottoes were carved on the face of a low ridge,
stretching 1km from east to west; there are 254 caves and some
51,000 statues. It is one of the most extensive grottoes in China,
covering approximately 18,000m 2 .
In order to preserve and utilize the culture heritage resources
better, Yungang Grottoes Research Institute and our college
worked together to find the suitable way to construct grottoes’
digital documents. After analysing and comparing to existent
survey technologies TLS was employed to do the job. In order
to assure it feasible and productive some grottoes were selected
to do a test. The relative field data captured works had been
done, the successive data processing works began on May 2007.
3. REGISTRATION METHODS REVIEW
Today, various ways are available to register point clouds to
each other. In general these ways can be classified three basic
methods according to their work styles (Geoff Jacobs, 2005).
Each of them is described below in detail.
3.1 Method 1: Populating a survey network with scans
This registration methodology is the one most likely to
traditional surveying. A control network is established firstly
and then each individual scan is tied to the control network as
an independent task. The scans are registered “to each other”
only in a relative sense, based on how well each scan is
individually tied to the control network. If one scan is not tied
