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.,
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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