RADIOMETRIC QUALITY AND DSM GENERATION ANALYSIS OF CARTOSAT-1 
STEREO IMAGERY 
M. Crespi 3 , L. De Vendictis c , D. Poli b , K. Wolff 0 , G. Colosimo 3 , A. Gruen b , F. Volpe c 
a DITS - Area di Geodesia e Geomatica - Sapienza Università di Roma - via Eudossiana 18 - Rome, Italy - 
mattia.crespi@uniromal .it 
b Institute of Geodesy and Photogrammetry, ETH Zurich, Wolfgang-Pauli-Strasse 15 8093 Zurich, Switzerland - 
<armin.gruen,daniela.poli,kirsten.wolff>@geod.baug.ethz.ch 
c Eurimage S.p.A. - via D’Onoffio 212 - Rome, Italy - <volpe,l.devendictis>@eurimage.com 
Commission I, SS-11 
KEY WORDS: Accuracy, DEM/DTM, High resolution, Matching, Orientation, Radiometric Quality, Satellite, 
ABSTRACT: 
CARTOSAT-1, launched in May 2005, is equipped with two cameras, Aft and Fore, tilted along-track by -5° and +26° respectively, 
allowing the acquisition of stereo data with a geometrical resolution of 2.5 m. The Institute “Area di Geodesia e Geomatica” at 
Sapienza Università di Roma, Eurimage S.p.A. and the Institute of Geodesy and Photogrammetry, ETH Zurich participated in the 
ISPRS-ISRO Cartosat-1 Scientific Assessment Programme (C-SAP), in order to investigate the generation of Digital Surface Models 
(DSMs) from Cartosat-1 stereo scenes. This paper follows up on the previous work done by the Institutes and shows the analysis of a 
new standard stereopair belonging to the additional test field TS-Castelgandolfo, acquired on 18th July 2006 over the area of 
Castelgandolfo, Rome, Italy (30 x 30 km 2 ). The images are processed, in order to test both the image quality and the potential for 
DSM generation, following the procedures already established. The results obtained in all steps of the investigation, particularly 
those related to image quality, the orientation with different models and software and the effectiveness of image filtering for 
enhancing the DSM generation are presented and discussed. 
1 INTRODUCTION 
CARTOSAT-1, launched in May 2005, is equipped with two 
cameras, Aft and Fore, tilted along track by -5° and +26° 
respectively, allowing the acquisition of stereo data with a 
geometrical resolution of 2.5 (Krishnaswamy, 2002). 
The Institute “Area di Geodesia e Geomatica” at Sapienza 
Università di Roma, Eurimage S.p.A. and the Institute of 
Geodesy and Photogrammetry, ETH Zurich participated in the 
ISPRS-ISRO Cartosat-1 Scientific Assessment Programme (C- 
SAP), in order to investigate the generation of Digital Surface 
Models (DSMs) from Cartosat-1 stereo scenes (Kocaman et al., 
2008, Baltsavias et al., 2007, Barbato et al., 2007). 
This paper follows up on the work done with the stereopair 
belonging to the test field called TS-6, acquired on 8th June 
2005 over the city of Rome, Italy, which was a very preliminary 
(just about one month after the launch) non-standard acquisition 
(7.5 x 30 km 2 ), since only a short part of the CCD array (3000 
pixels vs. a total of 12000) was active. The results of this part of 
the work were presented in (Barbato et al., 2007). Now a new 
standard stereopair belonging to the additional test field TS- 
Castelgandolfo, acquired on 18th July 2006 over the area of 
Castelgandolfo, Rome, Italy (30 x 30 km 2 ) is processed in order 
to test both the image quality and the potential for DSM 
generation, following the procedures already established. 
The results obtained in all steps of the investigation, 
particularly those related to image quality, orientation with 
different models and software, effectiveness of image filtering 
for enhancing the DSM generation and the potential of DSM 
generation itself are presented and discussed. 
2 DATA DESCRIPTION 
The dataset TS-Castelgandolfo of C-SAP contains a stereopair 
from the Cartosat-1 satellite with corresponding metadata files, 
the monographs of 25 ground points and a Digital Surface 
Model (DSM) derived from aerial images. 
The two stereo images were acquired on 18th July, 2006 in the 
morning, over Castelgandolfo and Colli Albani, a volcanic area 
Southeast of Rome. The scenes have a time interval of 54 sec 
and an in-track overlap of almost 90%. Each image has the size 
12’000 pixel x 12’000 pixels, with a ground resolution of 2.5 m. 
The area is characterized by the presence of volcanoes, crater 
lakes and isolated villages. The elevation ranges between 50 m 
and 1000 m. 
The scenes were acquired in panchromatic mode with mean 
attitude angles (roll, pitch, yaw) of (-11.3, 0.0, 2.49) degrees 
respectively. The metadata files contain information on the 
acquisition time, scene location, mean attitude angles, sensor 
geometry (detectors looking angles) and satellite orbit. The 
state vectors of the sensor (position and velocity) during the 
acquisition were not available. 
In addition to the satellite images, a block of 31 aerial images, 
arranged in 5 strips and covering an area of about 85 km 2 in the 
central part of the images from Cartosat-1, are available. They 
were used to generate a reference DSM. The aerial block was 
acquired during 2003 with a Wild RC-20 camera (lens type 
15/4 UAGA-F, focal length 152.18 mm) at an average scale of 
1:15000 with an along-track overlap of 70 % and a cross-track 
overlap of 20 %. For block orientation, 26 well distributed