The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Voi. XXXVII. Part Bl. Beijing 2008
P , P s , P 3 P 4 P 5 represent five vector points on the slave
track with separate UTM time / t s2 t s3 t s4 t s5 ■
The track point C m stands for the center of master image with
its time t and C the center of slave image with its time t .
In the practical baseline estimation, we must obtain the
parameters of points C m and C ms ■ And then the length of
baseline B can be calculated by the distance between
points C m and C ■ Equ.14 shows this process.
c m =(x.(U,rjUJJU)
B = C ms -C m
There are two major methods of baseline estimation [4]. They
both root in a fact that the projective value of B on the Z axis
is zero, namely B_ = 0 • The function extremum method expects
the least value of|i?|. When the equ.15 reaches its least value,
this value is the length of baseline. The vector method
considers the speed of satellites at the point C m as a vector.
Then the restraint condition is converted into Equ.16.
B\ = \a _+a ,t + a J +a J -X
sO il
s2
s 3
(/ )) 2 +lb +b t + b t 2 +b t 2 -Y (t )f+(<
\cmll \ sO si s2 s3 m y cm f \
; n +c .t+c .t 2 +c .t 3 -Z (t )
s0 si s2 s3 m cm
V-B = V-(C m -CJ = 0
(15)
(16)
3. EXPERIMENT AND ANALYSIS
We used a pair of SAR images obtained from JERS-1 SAR
sensor to examine algorithms for baseline estimation, flattening
phase and elevation computation. First, we simulated master
and slave tracks by information stored in SAR images to obtain
parameters of baselines. The result we obtained was compared
with that of commercial software EV-InS AR as shown in Tab. 1.
Second, we applied the algorithm based on PCM for flattening
phase to the raw interferogram. Then we compared the output
with that of method from ACM as illustrated in Fig.4. Third,
the step of elevation computation was implemented in three
ways including algorithm based on PCM, method from ACM
and EV-InSAR. Three results were discussed in details shown
in Fig.5.
method
Length of baseline (m)
Horizontal baseline (m)
Vertical baseline (m)
algorithm based on PCM
1115.2398205
1034.679468
416.170847
EV-InSAR
1115.378919
1036.43479826
412.156574423
Tab.l comparison of baseline estimation
Fig.4 output of flattening phase, the left one is the result of algorithm based on PGM and the right is output of AGM
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