International Archives of the 
  
      
Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004 
  
   
     
     
   
      
     
   
     
   
  
  
   
    
   
    
   
  
  
   
   
  
  
  
    
   
  
     
   
    
  
    
   
     
     
    
simultaneously. Positioning and attitude data is acquired by 
GPS (Global Positioning System) and IMU (Inertial 
Measurement Unit) List of sensors which is used in this 
research is shown in Table 1. 
  
Specification 
3072x2048 pixels 
Focus length 24.0mm 
Sensors Model 
  
Digital Canon 
Camera EOS D60 
Laser SICK 
Scanner LMS291 
Angular resolution: 0.25? 
Max. Distance: 80m 
Observation Angle: 100? 
IMU Tamagawaseiki Range 
TA7572 Angular Velocity +200°/s 
Accuracy 
Angle +0.1° 
Angle Velocity £0.05°/s 
Acceleration +0.002G 
GPS Ashtech Accuracy Differential 40cm 
G12 Velocity Accuracy 0.1(95%) 
Table 1. List of sensors 
  
  
  
  
All the sensors are tightly fixed on the mobile platform to have 
constant geometric relationship and they are controlled by 
common laptop PC to synchronize the laser scanning and taking 
images with the movement or direction of the platform. Figure 
1. shows the system design of this research. In this system, two 
laptop PCs are used. There two laptop PCs are synchronized by 
| pps (pulse par second) data of GPS. Table 2 shows the 
frequency of data acquisition. 
  
IMU GPS(G12) RAW 
  
A 
  
  
  
  
  
I Hz 
200Hz 
Eh 
  
  
Y 
[rom 
  
  
Laptop PC Laptop PC 
  
  
  
  
  
  
  
  
  
  
  
0.1Hz - 
18Hz 
Digital Laser 
Camera Scanner 
  
  
  
  
  
Figure 1. System design 
  
  
  
  
  
Sensors Frequency 
Digital Camera 0.1 Hz 
Laser Scanner 18 Hz 
IMU 200 Hz 
GPS I Hz 
  
Table 2. Frequency of data acquisition 
1.3 Platform 
In this research, all the measurement tools are loaded on a 
unmanned helicopter, RPH2, which is made by SUBARU. It is 
shown in Figure 2. And Table 3 shows the main specification of 
RPH2. And all the sensors are tightly fixed under the unmanned 
helicopter. When the experimental measurement is conducted, 
the unmanned helicopter flies about 1.8m/s of speed for getting 
enough resolution of data. 
  
Figure 2. SUBARU RPH2 
  
  
  
  
  
  
  
Weight 330 kg 
Pay load 100 kg 
Motor 83.5 hp 
Main Rotor Diameter 4.8m 
  
Table 3. Specification of RPH2 
2. SENSOR CALIBRATION 
Calibrations of sensors are necessary due to two reasons; to 
know the image distortion and to know relative position and 
attitude of each sensor against IMU. All the sensors are fixed 
on the unmanned helicopter to establish rigorous geometric 
relationships. The purpose of calibration is basically to integrate 
all the sensors and positioning devices to a single coordinate 
system, so that captured data can be integrated and expressed in 
terms of a single world coordinate system. 
2.1 Interior Orientation 
Calibration for digital camera is conducted to decide interior 
orientation parameters, principal point (xo, yo), focus length (f), 
and distortion coefficient (K,). Control points for camera 
calibration are taken as stereo images several times. Camera 
calibration is performed by the bundle adjustment using control 
points. Interior orientation parameters which are computed in 
this interior orientation are shown in Table 4. 
  
24.6906 mm 
1.5574E-008 
Xo 1532.9966 pixels f 
Yo 1037.3240 pixels K, 
  
  
  
  
  
  
Table 4. Interior orientation parameter 
In order to estimate appropriate lens distortion for digital 
camera, lens distortion mode is shown in Eq. (1) and Eq. (2). 
These equations consider only radial symmetric distortion. 
wh 
G 
ima 
vec 
X 
sysi 
Eq. 
Wh