The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
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Our investigations on Cartosat-1 data focus on: a) radiometric 
problems and preprocessing for image quality improvement, b) 
RPC refinement and 3D point measurement accuracy potential, 
and c) automatic DSM generation. The SAT-PP functions are 
used for RPC refinement, and DSM generation in this study. 
The sensor modeling is performed via Rational Polynomial 
Coefficients (RPCs). Two different models are applied to 
improve the given RPCs by using ground control points (GCPs). 
The RPC correction models include two translational 
parameters (RPC1) and 2D affine transformation (RPC2). 
Different numbers and distribution of GCPs are used for the 
investigations. 
The investigations in this paper are part of the ISPRS-ISRO 
Cartosat-1 Scientific Assessment Programme (C-SAP). IGP acts 
as principal investigator for some test sites and has evaluated 
data from other test sites. We have already reported on our 
investigations with the Rome and Mausanne test sites in 
Baltsavias et al. (2007). In this paper, we report on our 
investigations in the Catalonia test site (official C-SAP test site 
10), Spain, and Sakurajima test site, Japan. Other results 
regarding the Catalonia test site are reported in Lehner et al. 
(2007). 
2. INPUT DATA 
A Cartosat-1 stereo pair acquired over the Catalonia test site is 
provided by ISRO within C-SAP (Test site 10). The GCP image 
coordinates are measured at the DLR, Germany, using the Least 
Squares Matching (LSM) method (Lehner et al., 2007). Some 
details on the dataset are given in Table 1. The GCP distribution 
over the Cartosat-1 Aft image can be seen in Figure 1. As 
reference data, a DTM with a 15 m grid spacing and 
orthoimages with scale 1:5000 were provided by the Institut 
Cartografic de Catalunya (ICC), Spain for the whole testfield. 
The date of primary data acquisition for the DTM is unknown; 
this can result in differences in the comparison with the 
Cartosat matching DSM due to temporal differences. 
Imaging date 
01 Feb 2006 
Sun Azimuth 
Aft: 157.16918° 
Fore: 158.65601° 
Sun Elevation 
Aft: 31.65443° 
Fore: 28.91865° 
No. of GCPs 
70 
Point measurement 
69 points are measured with LSM and 
method 
1 point is measured manually 
Reference DTM 
29 km x 25 km 
- grid spacing 
15 m 
- accuracy (lo) 
1.1 
m 
- height range 
0 m-970 m 
Table 1. Catalonia Cartosat-1 test dataset description. 
The Sakurajima testfield is generated as a joint project of the 
Kochi Institute of Technology and Kanazawa Institute of 
Technology. 62 GCPs are provided by the Japan Association of 
Remote Sensing (JARS) and 61 points could be measured on 
the Cartosat-1 images (Figure 2). However, just a small area 
about 4 km to 4 km of the volcano Sakurajima is given as a 5m 
grid laser scanner reference dataset provided by Kokusai Kogyo 
Co. Ltd, Japan (see Figure 7). Main characteristics of the test 
site and the Cartosat-1 stereo pair are given in Table 2. 
ALOS/PRISM images acquired over the same test site are 
processed and the results are reported in Gruen et al. (2008). 
Figure 1. GCP distribution over the Cartosat-1 Aft image of the 
Catalonia test site 
Figure 2. GCP distribution over the Cartosat-1 Aft image of the 
Sakurajima test site 
Imaging date 
31 March 2006 
Sun Azimuth 
Aft: 139.17555° 
Fore: 143.38021° 
Sun Elevation 
Aft: 59.43782° 
Fore: 57.26630° 
No. of GCPs 
61 
Point measurement 
58 points are measured with LSM and 
method 
3 points are measured manually 
Reference DSM 
4 km x 4 km 
- method 
laser scanning 
- grid spacing 
5 m 
- height range 
300 m - 
-1100 m 
- remark 
no GCP inside reference DSM 
Table 2. Sakurajima Cartosat-1 test dataset description