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THE SIMULTANEOUS ADJUSTMENT FOR SPOT IMAGE USING 
ORBIT DATA AND A FEW CONTROL POINTS 
Y. Chen 
Xian Research Institute of Surveying and Mapping 
ABSTRACT: 
In this paper, the construction of the orbit data for SPOT image is described and the method 
using the data is discussed. The basic mathematical model for the simultaneous adjustment of 
SPOT imagery using the orbit data and a few control points are presented.The method can avoid 
the high correlation between the orientation elements during adjustment processing and 
decrease the number of necessary control points.Finally, the 
The results have proved that the solution 
of 
results of experiments are given. 
unknown points and orientation elements 
obtained by the mathematical model in this paper are of sufficient accuracy. An adjustment 
without ground control points sows that it is possible to determine positions of ground points 
using SPOT orbit data directly 
KEY WORLDS: SPOT orbit data, Imagery, 
1. THE CONSTRUCTION OF THE ORBIT 
DATA FOR SPOT SCENE 
Each SPOT CCT consists of five digital files. They 
are volume directory, leader, Image,trailer and null 
volume directory file. In which, the leader file is 
very useful for Photogrammetric processing. 
There are six records in the leader file. two records 
(header record and ephemeris-attitude ancillary 
record) can be employed for photogrammetric 
adjustment. The information included in these data 
are the following. 
1.1 Scene parameters 
Scene center geographic location (latitude, 
longitude) and corresponding image coordinates 
( scanline number, pixel number). 
Four scene corners geographic location and 
corresponding image coordinates . 
Scene orientation angle: complement of the angle 
between the center scene line of the raw scene and 
meridian through the center of the raw scene. 
Angle of incidence of SPOT sensor. 
Scene center time (universal time). 
67 
Orientation elements, Adjustment 
1.2 Ephemeris and attitude data 
Ephemeris data include the geocentric coordinates 
(Xc,Yc,Zc) of SPOT sensor position , velocity 
vector of the satellite movement corresponding to an 
instant and universal time. Generally, the 
coordinates for 8 or 9 sensor positions are given, the 
interval of time is 60 seconds. The Xc axis is in the 
equatorial plane corresponding to Greenwich 
meridian. The Yc axis is perpendicular to the Xc 
axis in equatorial plane. The Zc axis is along the 
earth polar axis. 
Attitude data include drift rate of attitude Pitch, 
Roll and Yaw for 72 or 73 points and 
corresponding scanline number, The interval of time 
is about 0.125 second. The Roll axis corresponding 
to the ¢ axis is the direction of SPOT orbit. The 
Pitch axis corresponding to the o axis is the 
scanning direction of sensor The Yaw axis 
corresponds to the x axis. 
2. THE PHOTOGRAMMETRIC SOLUTION 
FOR SPOT SCENE 
2.1 Coordinates system 
The basic coordinate system employed in this paper