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DEVELOPMENT OF DIGITAL SURFACE MODEL AND FEATURE EXTRACTION BY 
INTEGRATING LASER SCANNER AND CCD SENSOR WITH IMU 
Masahiko Nagai *, Ryosuke Shibasaki, Dinesh Manandhar, Huijing Zhao 
Center for Spatial Information Science, The University of Tokyo 
Cw-503, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505, Japan 
Tel: 03-5452-6417 Fax: 03-5452-6414 
nagaim@iis.u-tokyo.ac.jp 
TS SS-3: Mobile Multi-Sensor Mapping Systems 
KEY WORDS: Laser Scanning, CCD, IMU, Calibration, Model, Feature, Mobile, Platform. 
ABSTRACT: 
Three dimension data are in great demand for the various applications such as 3D GIS, navigation, digital archive, simulation, 
computer games, and so on. In order to represent space in details, it is indispensable to acquire 3D shape and texture together. 
However, there still lacks a reliable, quick, and handy method of acquiring three dimension data at higher resolution. In this research, 
we propose a combination of a digital camera and a small (cheap) laser scanner with inexpensive IMU (Inertial Measurement Unit) 
for unmanned air vehicles. 
3D shape is acquired by laser scanner as point cloud data, and texture is acquired by CCD sensor from the same platform 
simultaneously. Positioning data is acquired by GPS (Global Positioning System) and IMU. All the sensors are synchronized with 
movement or attitude of the platform. In this paper, a method of integrating all the sensors is focused. All the sensors are tightly 
fixed on the platform to establish rigorous geometric relationships. Calibration of laser scanner and CCD camera is conducted to 
know relative position and attitude of each sensor against GPS and IMU. Through Kalman filter, an optimal estimate of the sensor 
position and attitude is estimated from GPS and IMU. Bundle block adjustment is conducted using continuous CCD images. The 
result of bundle block adjustment aids Kalman filter by initialization of position and attitude. 
Using this measurement system, a procedure for automated construction of digital surface model is developed using these sensors. 
This paper proposes a new method of rendering objects with rich shape and detailed texture. Sensor position and attitude for 
mapping are basically acquired by GPS/IMU and their errors are complemented by digital camera images using tie point. In case of 
real time mapping, colored point cloud model is produced as a quick view. 
Feature extraction is conducted by range data and image data. Geometric shape which is acquired by leaser scanner represent 
features. Texture information, which is acquired by digital camera, details those features. That is, more detailed extraction is 
possible using both 3D shapes and colors. It is possible to extract not only man-made object but also natural object such as people 
and vegetation. 
1. INTRODUCTION 
1.1 Background 
Three dimension data is in great demand for the various 
applications such as 3D GIS, car navigation, pedestrian 
navigation, digital archive, simulation, computer games, and so 
on. In addition, targets of 3D data acquisition are now spreading 
to the 3D modelling of moving objects. In order to represent 3D 
space and moving objects in details, it is indispensable to 
acquire 3D shape and texture together efficiently (Zhao, H., 
Shibasaki, R., 2000). However, there still lacks a reliable, quick, 
cheap and handy method of acquiring three dimension data of 
objects at higher resolution and accuracy in outdoor and 
moving environments(Nagai, M., Shibasaki, R., etc., 2003). In 
this research, A combination of a digital camera and a small 
(cheap) laser scanner with inexpensive IMU and GPS for 
mobile platform are proposed. Using mobile platform is very 
important for acquiring data effectively(Zhao, H., Shibasaki, R., 
2001). That is, it is necessary to consider the method to get to 
develop the high precision positioning. In this research, the way 
  
of direct geo-referencing is achieved automatically from mobile 
platform using all the sensors without any ground control points. 
(Here, direct geo-referencing means geo-referencing which do 
not require ground control points with accurately measured 
ground coordinate values.) Therefore, after the accurate 
trajectory of the platform with attitude changes are determined 
through the direct geo-referencing, 3D shape of objects is 
determined by laser scanner as 3D point cloud data, while 
texture is acquired by CCD sensor from the same platform 
simultaneously. In this paper, a method of direct geo- 
referencing of range data and CCD images and integrating all 
sensors for constructing textured 3D model from the mobile 
platform are focused. 
1.2 System Design 
In this research, laser scanner and digital camera with IMU and 
GPS are used to develop digital surface model(Kumagai, H., 
Kubo, Y., 2002 and Kumagai, H., Kindo, T., 2000). 3D shape 
is acquired by laser scanner as point cloud data, and texture is 
acquired by CCD sensor from the same platform 
* Corresponding author. Masahiko Nagai Tel: +81-3-5452-6417 nagaim@iis.u-tokyo.ac.jp 
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