3-2-10 
Fig.4 Mean Square Errors (m) in X, Y and Z Axes for Conic Scanner 
4.Concluding Remarks 
To obtain high precision georeferenced imagery with high quality DEM for a variety of remote 
sensing applications, we must pay attention to the errors of each sensor in ALIMS. To improve the 
positioning accuracy of the system, priori calibration must perform carefully. The priori calibration 
includes the alignment of INS and LRMICS, the alignment of LFR’s footprints and corresponding 
pixels of multispectral imagery, the measurements of the difference between LRMICS and GPS 
receiver’s antenna etc. External information consist of height and horizon ground control points are 
very useful for improve the positioning accuracy of ALIMS. The adjustment must perform for the 
data that captured by ALIMS (In fact, we have developed two techniques for airborne laser 
scanning data adjustment and will become parts of Iconlnfo™, the information processing system of 
ALIMS). If some problems are solved properly (for example the accuracy of encoder that used to 
measure the angle of laser pulse and nadir, the accuracy of ranging etc), the positioning accuracy at 
the level of 1 to 2 decimeters can achieved by ALIMS when the system is well calibrated. For any 
kind of application, following problems must be considered: 
• The accuracy of any sensor in ALIMS has influence to the positioning accuracy of the system. 
From Eqs(4) and Eqs(4.a), We have the following conclusion that when the system is well- 
calibrated, the mean square error of the LFR’s footprint M x ,M y and M 7 are determined 
by the positioning accuracy of GPS (Wx s ’ m Y s > ^z s )> attitude accuracy of INS (171 ^, 171 M , 1YI K ), 
the accuracy of ranging 17l s and the angle accuracy the determined by encoder 171 $ . Any 
sensor accuracy decreases will cause the decreases of positioning accuracy of ALIMS. 
• When 171 x , 171 , 1712 S > Mg, ? , 171 K ,171^ , 171$ be fixed, the positioning accuracy of ALIMS is 
changed on scanning line. This is because coefficients of in Eqs(4) and Eqs(4.a) is the function 
of i9 and S when (p,CO,K is fixed for a specific scanning line. Laser-range-finder’s footprints