Pl-1-2 
following equation according to the geometry of 
interferometry. 
h=H-R\cos6 (3) 
If phase difference <t> is already known, 0 can be 
calculated by the equation 2. 
So, the elevation values are calculated according to the 
equation 3. 
But, it is difficult that the height of the satellite is 
determined precisely. 
Now, the next equation shows the partial differential 
equation of different phase against slant range and 
elevation. 
ty!m = 4ttBcos(0 - a)/ ARltan 0 (4) 
d(j)l ch. = 47rBcos(0- a)/AR\sinO (5) 
The equation 4 shows the proportion of different phase 
against the change of the slant range. So, it is shown the 
fringe when the surface of the earth is flat. That is why 
it is called the orbital fringe. 
The equation 5 shows the relation of phase difference 
and elevation. The elevation value is calculated from 
the difference of phase difference from the orbital 
fringe. 
PROCESS 
(1) Geometric Corresponding 
Geometric correction processing were carried out for 
corresponding to two SAR images. In this paper, 
corresponding points were selected better points into 
some candidate corresponding point by manual. 
(2) Calculation of the phase difference 
Subtracted the phase of SAR 1 from one of SAR 2. 
(3) Calculation of the orbital fringe 
The orbital fringe created according the equation 4. 
(4) Extraction the orbital fringe 
Subtracted the phase difference generated in (2) from 
the orbital fringe. If the elevation fringe is not appeared, 
regenerated the orbital fringe by changing the orbital 
position parameters. Because the orbital position data 
aren’t precise for interferometry processing. 
(5) Phase unwrapping 
The phase is distributed 0 to 2n. Therefore, the phase 
must be integrated. However, it is difficult to process by 
influence of the noise. Some methods were proposed, 
but the best one is unknown. 
(6) Conversion phase to DTM 
Convert from the integrated phase to elevation value 
according to the equation 5. 
RESULTS 
The following images are processed as input data. 
(1) JERS1 Level 0, 1993/07/07 
(2) JERS1 Level 0 , 1993/08/20 
The DTM were provided according to the next flow. 
The length of baseline is shown 818m by NASDA. 
The reference DTM data is used the 50m grid digital 
map data made by Geographical Survey Institute of 
Japan. 
Fig. 3 shows the estimated line. Fig.6 and Fig.7 shows 
the profile of the DTM on the estimated line. 
Fig. 2 The Flow of the Process