The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part BI. Beijing 2008 
pixel respectively. On further analysis using pixel versus scan 
difference comparison, it was found that there was no 
substantial yaw effect. This has prompted to arrive at a roll bias 
of 0.096 deg approximately and 0.119 deg in pitch bias in 
attitude angles. After incorporation of these values, estimation 
showed significant improvement in both directions and was put 
to use for product generation. Table 4 shows the improvement 
in mean error after accounting for biases. Additional 
refinement to biases was estimated subsequently as 0.083 deg 
for roll and 0.110 deg for pitch. DQE evaluated a number of 
products and the results show significant improvement (Figure 
5.0) in the location accuracy of products and was better than 
100m in most of the cases, thus meeting the mission 
specifications. 
Cases 
Mean 
Scan 
Error 
(pixels) 
Mean 
Pixel 
Error 
(pixels) 
No Of 
GCPS / 
TCPs 
Case 1 
1791.57 
1332.42 
114 (lm) 3 
Case 2 
1307.47 
1400.58 
11 (2.5m) 
Case 3 
1307.08 
1385.25 
10 (2.5m) 
Case 4 
1636.05 
1303.42 
11 (lm) 
Case 5 
1637.68 
1305.28 
39 (lm) 
Case 6 
1632.26 
1309.70 
10 (lm) 
Case 7 
1630.74 
1313.36 
15 (lm) 
Case 8 
1553.87 
1326.17 
15 (lm) 
Case 9 
1569.47 
1322.35 
13 (lm) 
d - values in ( ) indicate different input imaging resolutions 
Table 3.0 Cartosat-2 initial system level accuracy 
Cases 
Mean Scan Error 
(pixels) 
Mean Pixel Error 
(pixels) 
Case 1 
2.91 
34.58 
Case 2 
3.84 
31.66 
Case 3 
34.96 
12.72 
Case 4 
28.56 
16.67 
Case 5 
11.62 
30.50 
Case 6 
16.79 
23.29 
Table 4.0 Cartosat-2 improved system accuracy 
Period ( dd-mmm-yy) 
5. CONCLUSIONS 
One of the important activities undertaken during post-launch 
period for Cartosat-1 and Cartosat-2 was in-flight geometric 
calibration. Being a stereo mission, Cartosat-1 offered many an 
opportunity to understand various parameters and estimate 
them correctly through in-orbit calibration activities to improve 
the overall system performance. SST is one of the unique 
software identified for operational generation of DEM and 
TCPs for Indian region from Cartosat-1 stereo pair, whose 
abundant results strengthened the in-flight analysis work. It 
has been demonstrated that system level accuracy could be 
improved to meet the accuracy demands of various mapping 
applications with the help of in-flight exercises. Similar 
exercises were carried out for Cartosat-2 to improve the data 
products accuracy. This paper has briefly covered some of the 
in-flight geometric calibration experiences with Cartosat-1 and 
Cartosat-2 missions. 
REFERENCES 
Nandakumar R., Srinivasan T. P., Gopala Krishna B., 
Srivastava P. K., 2005. Data Products for Cartosat-1, ISG 
newsletter, Vol. 11, No. 2&3, Special issue on Cartosat, June & 
September 2005, pp. 18-24, ISSN:0972-642X 
Srinivasan T. P., Sanjay Singh, P. Neethinathan, Jagjeet Singh 
Nain, Amit Gupta, Gaurav Misra, B. Kartikeyan, Gopala 
Krishna B., Srivastava P. K., 2006. Stereo Strip Tringulation 
for Cartosat-1, Technical Commission IV symposium on 
“Geospatial Databases for sustainable development”, Goa, 
India. 
Srivastava P.K., Alurkar S. Medha, Inflight Calibration of IRS- 
1C imaging geometry for data products, ISPRS Journal of 
Photogrammetry and Remote Sensing, 52 (1997), pp. 215-221 
Tommaselli A. M.G, Tozzi C. L., A recursive Approach to 
Space Resection Using Straight Lines, Photogrammetric 
Engineering & Remote Sensing, Vol. 62, No.l January 1996 
Mikhail M.Edward, Bethel S.James, and McGlone Chris.J., 
2001. Introduction to Modern Photogrammetry, John Wiley & 
Sons, Inc 
ACKNOWLEDGEMENT 
The authors express their deep sense of gratitude to Dr. 
R.R.Navalgund, Director, Space Applications Centre, 
Ahmedabad for allowing us to take up and complete the work. 
Special thanks go to Shri. A.S.Kirankumar, Dy. Director, 
SEDA for his constant support, guidance and technical 
suggestions for both Cartosat-1 and Cartosat-2. Also, authors 
are thankful to Cartosat-1 project team, NRSA operations team 
and other data products team members for extending support to 
this exercise. Authors wish to thank the internal reviewers for 
their critical comments. 
Figure 5.0 Cartosat-2 Data Products accuracy