1215 
UAV BORNE MAPPING BY MULTI SENSOR INTEGRATION 
Masahiko Nagai, Tianen Chen, Afzal Ahmed, Ryosuke Shibasaki 
Centre for Spatial Information Science 
The University of Tokyo, Japan, 
435 Research Centers, CSIS, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8568, Japan 
Tel: +81-4-7136-4307 Fax: +81-4-7136-4292; 
nagaim@iis .u-toky o. ac .j p 
ThS-23: UAV for Mapping 
KEY WORDS: Laser Scanning, CCD, IMU, Calibration, Mobile, Platform. 
ABSTRACT: 
Three dimensional data is in great demand for disaster and environmental monitoring. In order to represent 3D space in details, it is 
indispensable to acquire 3D shape and texture together efficiently. However, they still lack a reliable, quick, cheap and handy 
method of acquiring three dimensional data of objects at higher resolution and accuracy in outdoors and moving environments. In 
this research, utilization of UAV (Unmanned Aerial Vehicle) is proposed. UAV is often used in military purpose, but also UAV is 
currently used in civil purpose such as mapping and disaster monitoring. UAV can fly lower altitude to get precise information and it 
is good for dangerous situation, however UAV has some limitations in terms of payload. It is difficult to mount aerial remote sensing 
sensors, so UAV mapping is still at the level of monitoring, not at the level of surveying. In this research, a combination of CCD 
cameras and a small (cheap) laser scanner with inexpensive IMU and GPS is proposed for an UAV borne 3D mapping system. 
Direct geo-referencing is achieved automatically using all the sensors without any ground control points. A new method of direct 
geo-referencing by the combination of bundle block adjustment and Kalman filter is proposed. This is the way of rendering objects 
with rich shape and detailed texture automatically by using an UAV. 
1. INTRODUCTION 
Aerial survey has become very valuable method for mapping 
and environmental monitoring. Remote sensors, such as an 
image sensor or a laser scanner, gather information about an 
object or area from a distance. Recently, some high resolution 
sensors has been developed for various purpose. They can cover 
widely target area and also archived data is available for users, 
but the spatial and temporal resolution is not always enough for 
detailed mapping. 
Field workers use to conduct ground survey by using an 
instrument called a total station (a small telescope equipped 
with an electronic distance measuring device), GPS, a laser 
scanner, digital camera and so on. Ground surveying is 
conducted on the ground, so generally it is very close to, or on, 
observation targets. Therefore, they can get detailed and 
accurate information, but these techniques take a lot of labors 
and expenses, and spending times for the surveying. Also, it is 
not always safety in the case of the stricken area. 
UAV borne mapping system is developed as an intermediate 
mapping system between aerial survey and ground survey in 
terms of coverage and spatial resolution. All the measurement 
tools are mounted on the UAV to acquire detailed information 
from low altitude which is different from a satellite or a plane. 
The survey is carried from the sky, but the resolution and 
accuracy are the same level of the ground surveying. The data 
can be easily acquired collectively with safety and mobility by 
the utilization of an UAV. 
Measurement Unit) and GPS for mobile platform are proposed. 
The method to integrate these sensors should be developed for 
the high precision positioning system in moving environment 
(Nagai and Shibasaki, 2006). In this research, the way of direct 
geo-referencing is achieved automatically from mobile platform 
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. The 
methods of data acquisition and digital surface model are 
developed with the method of direct geo-referencing of laser 
range data and CCD camera with GPS and IMU from an UAV. 
2. SYSTEM DESIGN 
2.1 Sensors 
In this research, laser scanner and CCD cameras (digital camera 
and IR camera) with IMU and GPS are used to construct digital 
surface model. In order to construct digital surface model 
automatically, it is necessary to develop the high precision 
positioning system in all circumstances for determining the 
movement of sensors. Integration of GPS/IMU is very effective 
for high accuracy positioning of mobile platform. 3D shape is 
acquired by laser scanner as point cloud data, texture 
information is acquired by digital camera, and vegetation 
indexes are acquired by IR camera from the same platform 
simultaneously. List of sensors which is used in this research is 
shown in Table 1. 
The key points of the system design are to realize “Handiness” 
and “Mobility” of the system. “Handiness” means low cost, 
easy method and process. Utilization of a small laser scanner, a 
In this research, a combination of a CCD camera and a small 
(cheap) laser scanner with an inexpensive IMU (Inertial