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