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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004 
other is tilting error and also defined by angles (Aa;,AB;) in X, 
Y axis respectively. In order to correct the above errors, two 
kinds of correction targets were adopted in the actual 
measurement. One is a vertical target and used for adjusting the 
vertical, i.c. Z axis. The other is a direction target and for 
adjusting scene rotation with the vertical point as its central 
position. This process is to adjustment axes. 
Figure 5 illustrated the cross section of measurement and 
correction targets deployment. (Ti,i=1,4) is a direction target. 
The vertical target is hanged from the scanner original position. 
  
  
  
  
— 240 gm am Em am 8m 8m 8m _ 
10m 
-———— | ?m 
© © A 20 
C41 es TRE my 
ae 15m 
Ci (i=1.4) : Measurement Points Vertical Target 
T4 13, T2 Ti 3m 
Ti (21,4) : Direction Targets ' Coverage af Measurement 
  
Figure 5. Measurement Coverage and Deployment of 
Correction Targets 
Bright blue triangle corresponds to one measurement and its 
coverage. Consequently four measurements are necessary at 
one arm direction. 
Within coverage of one measurement, at least two direction 
targets and one vertical target are included. One vertical target 
is identified in obtained data with specific distance and a tilting 
error angle is calculated by its position. According to the same 
process, a rotating error angle is introduced by the difference 
between line ((T;)-(T;+,)) and Y axis with the vertical point as 
its central position. 
33 Measurement 
  
Figure 6. Actual Targets and Target Canopy 
Figure 6 shows the picture which took from the crane arm in the 
actual measurement. The left edge of this picture is the central 
position of used crane. The green rectangle area is one 
measurement area (Scene-1). The continuous yellow rectangle 
is the next measurement area (Scene-2). On Scene-1, two 
241 
direction targets can be seen. Around the right edge, gondola 
with circle shape and vertical target with white point can be 
also seen. Between Scene-1 and Scene-2, overlapped area is 
allocated by the consideration of scenes mosaic. 
On the other hand, the crane stands at the center of 4ha plot 
where all individual trees (DBH: Diameter Blest Height > 
10cm) have been investigated in every 10X10m patch area as 
minimum unit and identified to species. 400 patch areas had 
totally set up within 4ha plot using survey pins. Using these 
pins, the ground survey for identifying pins’ location with 
geographic location (X, Y, Z) had been done. 
3.4 Data Processing for DSM and DEM Generation 
Data processing procedure for obtained measurement row data 
is illustrated in figure 7. 
  
Measurement Row Data 
Tilting Error( A 9, A f) Correction 
Adjustment Vertical Axis 
Conversion 3D Data 
Rotating Error( A ®) Correction 
| | 
| Coordinate System Integration and Add Geographic Location | 
Scenes Mosaic 
DSM Generation 
    
Acquisition of 
Measurement Position 
with Geographic Location 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Figure 7. Data Processing Procedure 
3.4.4 Data Acquisition and its Data: Acquired row 
data consists of the distance (L) from the laser beam original 
position to the target surface and angles in X, Y axes with 0.25 
degree resolution. Also the location of measurement point is 
identified by both GPS and crane operating system. 
3.4. Tilting Error Correction: The tilting errors 
(Aa, AP) are calculated by identifying targets. Using these 
values (Aa, Ap), Z axis is adjusted to the vertical axis. 
3.4.3 Conversion 3D Data: Equation (1) is the 
conversion from corrected row data to 3D data by considering 
tilting errors. 
L*sin(ai Aa;)cos(pi Ap;) 
L*cos(ai. Ao;) sin(Bi Af) 
L*cos(ai Ao;)cos(Bi AB;) 
N X 
| 
(1) 
Here, (X, Y, Z) is the converted 3D data. L is measured 
distance and i is the number of measurement point. 
Angles(Ao; A;) are the tilting errors in X,Y axes at point-i. 
Angles(ai, Bi) are the beam irradiating angles. 
3.4.4 Rotating Error Correction: The angles organized 
by the line between two direction targets with the center of data 
as the central measurement point, decide the rotating errors. 
Through tilting and this corrections, all measured coordinate 
systems could be integrated to the same coordinate system.