The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B7. Beijing 2008 
9 of the 49 points are selected auxiliary GCP, the remaining 40 
as CKPs. Equation 10 was used for calculation of RPC. 50 
GCP were used to get the initial value of RPC, and then BILSR 
and IDKF were both used to improve the RPC accuracy. The 
points were added into the equation one by one in IDKF for the 
use of 9 GCP (Because the auxiliary GCP usually have higher 
accuracy, they have higher power in calculation). In this test, 
all the GCP were collected at the same time with the same way, 
so they all had the same power. So the test here is to determine 
improvement efficiency of BILSR and IDKF for RPC accuracy 
after increase of GCP. The covariance matrix is set to 
Q = KT 6 to test the accuracy of updated RPC. Image points 
of 40 CkP were obtained using updated RPC according to 
equation (1). The errors of calculated image points and 
measured ones were used for analysis. 
The results of BILSR and IDKF are as table 3, where the mean 
square deviation, max absolute error and point position error of 
CkP in both row and column directions are given. 
The original row mean square deviation, column mean square 
deviation and point position error were 1.536, 3.431, 3.760 
pixels, respectively. The updated row mean square deviation, 
column mean square deviation and point position error with 
BILSR using 9 GCP were 1.467 , 3.315 , 3.625 pixels, 
respectively. The updated errors with IDKF using 9 GCP were 
1.494, 3.320, 3.641 pixels, respectively. The RPC accuracy 
was improved within 0.2 pixels after the addition of 9 GCP, for 
9 GCP was not notable compared with 50 GCP when it comes to 
adjustment (figure 5). 
Number 
of New 
GCP 
BILSR: pixel 
IDKF: pixel 
Row 
Column 
Point 
Position 
Error 
Row 
Column 
Point 
Position 
Error 
RMS 
MAX 
RMS 
MAX 
RMS 
MAX 
RMS 
MAX 
0 
1.536 
2.743 
3.431 
11.492 
3.760 
1.536 
2.743 
3.431 
11.492 
3.760 
1 
1.536 
2.748 
3.426 
11.484 
3.754 
1.531 
2.743 
3.426 
11.484 
3.752 
2 
1.541 
2.759 
3.398 
11.355 
3.731 
1.549 
2.756 
3.396 
11.352 
3.732 
3 
1.534 
2.756 
3.420 
11.430 
3.749 
1.531 
2.751 
3.422 
11.426 
3.749 
4 
1.549 
2.830 
3.448 
11.498 
3.780 
1.552 
2.768 
3.437 
11.479 
3.771 
5 
1.523 
2.816 
3.449 
11.514 
3.770 
1.544 
2.762 
3.457 
11.523 
3.786 
6 
1.536 
2.832 
3.445 
11.517 
3.781 
1.553 
2.761 
3.447 
11.456 
3.781 
7 
1.497 
2.708 
3.373 
11.335 
3.691 
1.515 
2.743 
3.375 
11.328 
3.699 
8 
1.483 
2.691 
3.342 
11.174 
3.657 
1.497 
2.721 
3.345 
11.185 
3.665 
9 
1.467 
2.674 
3.315 
11.120 
3.625 
1.494 
2.733 
3.320 
11.125 
3.641 
Table 3 Results of BILSR and IDKF by adding GCP by sequence 
-»-Position RMSE of BILSR -»-Position RMSE of IDKF 
3. 80 
~ 3.75 
!,™ 
I 3.65 
os 
J 3.60 
£ 3.55 
3. 50 
50 51 52 53 54 55 56 57 58 59 
Number of GCPs 
Figure 5 Compare of Point Position Error between BILSR and IDKF 
1292