665 
In: Wagner W., Sz£kely, B. (eds.): ISPRS TC VII Symposium - 100 Years ISPRS, Vienna, Austria, July 5-7, 2010,1 APRS, Vol. XXXVIII, Part 7B 
Where R = the slant range from objective to sensor 
R sc = the position of sensor 
R tc = the position of objective 
V sc = the velocity of sensor 
f d = the central duppler frequency 
X = the wavelength 
The first equation is the range equation, the other is duppler 
equation. Model parameters can be extracted original image 
parameter file, in the solution process of the model calculation 
need to know the sensor orbit information. Along with the 
development of inertial navigation technology, currently a 
number of SAR satellites have been able to provide very. When 
there is no accurate sensor orbit, the sensor orbit can be 
inversed with a certain amount of image control points. 
2.2 Image Simulation Parameter 
Simulation parameters mainly contain simulated imaging orbit 
parameters and simulated image parameters. Orbit parameters 
are mainly orbital altitude, orbital direction, image parameters 
are mainly imaging resolution. 
Generally, the simulated orbital altitude is approximately equal 
to the original SAR image orbital altitude. The re-sampling 
direction is the same as the range direction of original image 
normally, and perpendicular to the orbital direction. For 
example, the orbital direction for Spacebome SAR is roughly 
north-south direction, simulated imaging orbit can be true 
north-south direction and re-sampling direction is west-east 
direction. Simulated image resolution depends on mapping 
resolution or mapping scale. The following briefly on what set 
the principle of simulated orbital parameters. 
Imaging region can be determined by the coordinate of four 
comers of the original image. The simulated orbit direction is 
set to be Y direction. Then in the Fig.l is a re-sampling scan 
line. The bound coordinate X b is from imaging region, orbital 
altitude is set to be H . R^ is equal to the nearest slant range of 
original image. So the orbital X -axes coordinate is X s : 
Figure 2. Baseline 
In order to obtain well imaging results, the base-height ratio 
should be designed before simulation. The designed base-height 
ratio can be obtained with moving simulated imaging orbital 
position. As the Fig.2, the orbit is moved, and then the orbital 
X -axes coordinate after moving is X . 
2.3 Simulated Image Geo-location 
It is necessary to establish the map between simulated image 
coordinates and geographic coordinates. The geographic 
coordinate Y of corresponding point on simulated image can be 
obtained from the orbital position, while X needs to be solved 
with DEM and simulation imaging model (central projection 
imaging model or slant-range projection imaging model. The 
coordinate X and the elevation is obtain through iterative 
solution, the principle is: 
1) . set initial value of elevation h Q ; 
2) . solve X 0 with the initialization; 
3) .interpolate from DEM with X Q and Y ; 
4) . sol ve X x with }\ ; 
5) .circling iteratively until \X M — X^ < 8 , the geographic 
coordinate is {X j , Y, h { ) ; 
For the slant-range projection imaging model, the iterative 
solution depends on the slant-range equation: 
(2) 
Get elevation information from DEM and solve the geographic 
coordinates. The Fig.3 is sketch map and procedure of iterative 
solution.