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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