ution 
znals 
eter. 
ation. 
pting 
lite's 
itput 
nage 
tude 
form 
ality 
the 
) the 
focal 
1 it 
N by 
rray 
  
  
  
T,= pr/v 
  
  
Fig.1 The way of scanning. 
As shown in Fig.l, an n pair of 1-D CCD 
array advances with a velocity relative to the 
surface of the earth V , taking of the earth 
images those are apart by Py from each other in 
the direction of satellite movement. The time 
difference between each CCD image taking at 
the same point 1s 
tp=Py/V. (1) 
When the distance between each CCD is 
equal, the output signal can be increased to M 
times the signal by adding the time of 7 p 
integral times to each CCD output signal that is 
picked up at the same point of each line. 
The improved ratio Smpr(n) of the signal 
output is calculated as follows: 
s S u m pp(n) : 
S im pr V N = = ———=—————_— 2 
wA Sum pp(l) © 
where Sumpp(n) and Sumpp(l) are output 
amplitude values with TDI method and without 
TDI method. respectively. 
On the other hand, the amount of random 
noise is increased 4n times by integrating n 
times. Therefore, the improved value S/Nimpr(n) 
of the S/N is calculated as follow: 
Simpr(n) 
Jn ED ©) 
S/N impr(n) = 
2-2 MOVEMENT CHANGES AROUND 
AXIS 
Imaging position on earth, as shown in Fig.2, 
is affected by the movement changes around 
each roll, pitch, and yaw axis. 
For every time difference % », we definite 
the rotating angle around each roll, pitch, and 
yaw axisas ó,, ó, and ö, respectively. Thus, 
each image position change defined as 
previously to be Æ:W : , K,W , can be expressed 
by the following relationships. 
y 
0 
«2 © ) 
ó, ô 
p 
H mmm 
k Wx 
k,w, 
x 
wu LU 
(a) roll axis (b) pitch axis (c) yaw axis 
  
  
  
  
Fig.2 Movement changes around axis. 
2-2-1 MOVEMENT CHANGES AROUND 
THE ROLL AXIS 
The movement changes around the roll axis 
appears in parallel to the scan direction X when 
the height of the satellite from the earth is H, 
the following equation is established: 
k.w . 2 Hó. (4) 
Intemational Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998 17 
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