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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