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The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
should less than 1. Experiments show the result is optimum 
when a value gets 0.1 or so. 
2.2.2 registration with least square fitting method 
Using high-precision control points, according to formula (1) , 
geometric distortion rectification is carried out on complex 
images of homologous stereopair,then, calculate iteratively out 
the six distortion parameters according to formula(7) in the 
following : 
a o =a o ' + da» ' + a 0 ‘~'daf' + b 0 ‘~'da 2 
a { ‘ = af' +af'daf' + bf'da 2 
a 2 = a 2 ' + a i 'dai ' + b 2 ‘ 'da 2 
a 0 — b 0 + db 0 + a 0 db( + ò 0 db 2 
a,' =6/ 1 +af'dbf l + bf'db 2 
b 2 = b 2 "I - a 2 db x + db 2 
Among them 
Ì—1 I 
a Q i a \ ’“2 
7-1 _/-l Ì-1 »7-1 » 7-1 »7-1 
5 Cl2 5 Oq 5 ¿U 
i indicates iterative times, 
0 ,l/ * ,i ' 2 is distortion parameter of the 
preceding once, da 0 ,da x ,da 2 ,db 0 ,db x ,db 2 correc ^ on va i ue 
of iterative calculation of this time. 
3. INTERFEROGRAM PRODUCTION AND REMOVAL 
OF THE PHASE OF FLAT EARTH 
As we know, the single image’s phase of interferometry is of 
little significance, phase difference between homologous image 
points must be obtained, namely o = 7^(6^, — 6> 2 ), calculation 
indicates O is in the range of [0,2x) ■ 
Because homologous complex images may be expressed as 
follows: 
m, =|w 1 |e ;01 = a, +bf, 
it 2 = \u 2 \e j61 = a 2 + b 2 i 
J°.2 * I 
? j02 - |M 1 ||M 2 |e /(<?l 82} 
= {a^a 2 + bf 2 ) + (a 2 b^ - af 2 )i 
So A- 
<f) = w(arctan[- 
ct 2 b\ a f> 2 
]) 
ct,ct n + b,b- 
According to this principle, interferogram can be produced, and 
its phase is fuzzy about 2ît, which is made up of two parts: the 
phase component caused by terrain relative elevation, and that 
caused by flat earth, when the elevation of two points on the 
ground are the same, as figure(l) shows, phase difference 
obtained in P V P 2 should be equal if there is no difference in 
phase difference caused by flat earth, but the oblique distance 
image-forming characteristic of INSAR results in phase 
difference displacement of the two pointsP ]2 P 2 ■ Therefore,any 
original interferogram needs subtracting phase difference ^ 
caused by effect of flat earth from original phase difference of 
each point in the distance direction. Ultimately, the removal of 
phase of flat earth finishes, thus, the achieved interferogram is 
just the one corresponding to the topography. 
And phase difference ^ is : 
= 4;zn 5 Ar/(/l*r 0 *tan#) 
n s is baseline distance component perpendicular to oblique 
distance , oblique distance difference, T 0 the length of 
oblique distance, and 0 the angle of incidence. 
S2 
Fig-(l) 
According to satellite track parameters provided by European 
Space Agency ,the satellite track attitude may be expressed as 
linear function of time or low order polynomial, as the formula 
(11) shows: 
X = a n + a,t + aJ + aJ + a.t 
(ID 
Among them: X i s a coordinate (including X,Y,Z coordinate) of 
satellite, and T is the time . 
In general, the satellite track parameters include 0 X the angle 
of incidence of short distance, 63 the one of long distance, 
and 6 2 the one of middle point between 6 X and 0 3 in the 
distance direction.so any angle of incidence 6 in image may 
be expressed in formula (12): 
6 = ay 2 +by + c 
(12) 
Among them: y is the ratio of row coordinate and the width of 
the whole frame image, a,b,c is coefficient of fitting, the value 
of a,b,c can be calculated by 0 V 6 2 ,0 2 \ Meanwhile, terrain 
surface is fit by using several ground control points , like the 
formula (13): 
X = a 0 + a { x + a 2 y + a 3 xy + a 4 x 2 + a 5 y 2 
(13) 
Among them: X is the coordinate (including the coordinate 
X, Y,Z ) of points on the ground, x is the column coordinate of 
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