The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part BI. Beijing 2008 
1312 
Pt, ID 
X 
Y 
DSM Z 
DEM Z 
Residual 
4 
464147,98 
5738939,12 
163,55 
163,06 
-0,49 
8 
451384,13 
5739462,83 
162,63 
162,9 
0,27 
10 
463566,51 
5738103,00 
165,79 
165,26 
-0,53 
14 
450570,68 
5734109,76 
138,05 
138,32 
0,27 
16 
460284,13 
5730408,02 
169,65 
167,44 
-2,21 
26 
449046,65 
5724779,93 
163,82 
164,24 
0,42 
Table 3: Detailed Check Point accuracy information 
The DSM assessment included inspection of the cross sections 
measured during the field survey. The cross section distribution 
in the stereopair was as on the illustration (Fig. 6.). 
Figure 6: Cross sections distribution on after scene. 
The cross sections are 3.5 km long each and the distance 
between the measured points is about 20 m. The automatically 
calculated cross sections and the ones measured during the field 
survey using GPS PSK method were found strongly correlated. 
The graphs below summarize the correlation between the DSM 
and the GPS RTK measurements taken during the field survey. 
All graphs illustrate values calculated using LPS 9.2 SP1. 
Clearly the correlation is very strong - up to 0.95 (Fig. 7). This 
ultimately proved the high fidelity of the DSMs based on 
stereopairs acquired by Cartosat-1 satellite. 
1 .0.95 
1 » «I » 101 128 m 
potili 
}.0.94 
1 n si n 101 1» til 
Figure 7: Cross sections and their correlation values. 
8. ORTHORECTIFICATION 
The orthorectification was conducted using the DSM, which 
was calculated with LPS 9.2 SP1. The resolution was set to 2.5 
m and the after scene and 3 m for the forward scene. Both 
orthoimages matched precisely which implied the accuracy of 
the DSM was sufficient for high resolution orthoimaging. The 
images were also highly compatible with the field survey data. 
As an additional measure the orthoimage from the satellite was 
visually compared to independently acquired orthoimages from 
another IRS satellite (IRS P-6 Resourcesat). The results again 
confirmed the high accuracy of the orthoimage. 
9. CONCLUSION 
The findings included in this paper reflect the high accuracy of 
stereo data produced by Cartosat-1. The images acquired by the 
satellite can be safely used for the purposes it has been designed 
for (Srivastava, 2007) i.e. gathering elevation data with 
accuracy sufficient for maps with the scale of 1:25000. Digital 
Elevation Models based on the stereopairs from Cartosat-1 are 
sufficient for generating orthoimages with the resolution of 2.5 
m (Cartosat-1, SPOT) or lower (IRS). 
REFERENCES 
Dqbrowski R., Kedzierski M., Fedorowicz-Jackowski W., 
Walczykowski P., Zych J. 2006/1. Precision analysis of DEM 
obtained from Cartosat-1 stereo data. Proceedings of ISPRS 
International Symposium on Geospatial Databases for 
Sustainable Development, Goa, India 27-30 September 2006 
Dabrowski R., Kaczynski R., Kedzierski M., Fedorowicz- 
Jackowski W., Zych J. 2006/2. Geo-interpretation capabilities