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MULTI-SCALE DIGITAL TERRAIN MODEL GENERATION USING CARTOSAT-1 
STEREO IMAGES FOR THE MAUSANNE LES ALPILLES TEST SITE 
Marco Gianinetto 
Politecnico di Milano, Remote Sensing Laboratory, DIIAR Dept., Piazza Leonardo Da Vinci 32, 20133 Milano, Italy — 
marco. gianinetto@polimi. it 
Commission I, SS-11 
KEY WORDS: Satellite remote sensing, Digital elevation models, Space photogrammetry, Accuracy analysis, Topographic 
mapping 
ABSTRACT: 
Cartosat-1 is the first Indian Remote Sensing satellite able to collect in-track high resolution stereo images with a 2.5m pixel size. 
Since Cartosat-1 has no multispectral cameras, it was mainly developed for topographic mapping and Digital Terrain Model (DTM) 
generation. In the framework of the Cartosat-1 Scientific Assessment Programme, the Politecnico di Milano University (Italy) 
evaluated as Co-Investigator the performances of the Cartosat-1 satellite in the generation of DTMs from stereo-couples. This paper 
describes in detail the outcomes for the Mausanne les Alpilles (France) test site, with respect to existing standards and products 
actually used in France and also provides a comparison with the global Shuttle Radar Topography Mission’s DTM supplied by 
NASA and widely used in the remote sensing community. 
1. INTRODUCTION 
Cartosat-1 is the first Indian Remote Sensing (1RS) satellite able 
to collect in-track high resolution stereo images with a 2.5m 
pixel size. Since Cartosat-1 has no thematic capabilities (no 
multispectral cameras), it was mainly developed for 
topographic mapping and Digital Terrain Model (DTM) 
generation. 
At the beginning of 2006 an agreement has been reached 
between the International Society for Photogrammetry and 
Remote Sensing (ISPRS) and the Indian Space Research 
Organisation (ISRO) to jointly conduct the Cartosat-1 Scientific 
Assessment Programme (C-SAP), whose purpose was to 
evaluate the Cartosat-1 mapping capabilities in the following 
processes: 
■ Photogrammetric stereo triangulation at scene level; 
■ Photogrammetric stereo triangulation at block level 
(multiple scenes); 
■ Extraction of terrain features for topographic mapping; 
■ DTM generation; 
■ Topographic mapping. 
Within the C-SAP framework, Politecnico di Milano University 
(Italy) was selected as Co-Investigator for the French test site of 
Mausanne les Alpilles (C-SAP TS5) and this paper describes 
the outcomes of the investigation carried on in the assessment 
of the DTM’s generation. 
Results were compared with respect to existing standards and 
products actually used in France (i.e., the French Institut 
Géographique National’s and Spot Image’s Reference 3D®). 
Moreover, the investigation also provided a comparison with 
the global Shuttle Radar Topography Mission (SRTM) DTM 
supplied by NASA and widely used in the remote sensing 
community (Van Zyla, 2001). 
Imagery collected with Cartosat-1 were used for the generation 
of: i) high-resolution DTMs (from 2.5m to 10m grid cell size), 
ii) medium-resolution DTMs (25m grid cell size), and iii) low- 
resolution DTMs (90m grid cell size) using commercial off-the- 
shelf software. This choice was made to provide to the remote 
sensing users a comprehensive study about the potentialities 
and limits of the Cartosat-1 image processing using standard 
image processing software. 
2. DATASET 
2.1 Test site 
Mausanne les Alpilles sits in the hart of Provence (France), in 
the triangle of Arles, Avignon and Marseille. An area of about 
650 km 2 of overlap between the Cartosat-1 images and the 
reference DTMs has been selected as test site (upper left: 
4,854,403m N, 633,411m E; lower right: 4,835,486m N, 
655,172m E). Here the elevation ranges from 47m in the south 
west to 633m in the north-east and the territory presents a 
mixture of rural areas (60%), green forest (35%) and urban 
areas (5%). 
2.2 C-SAP dataset composition 
The standard C-SAP TS5 dataset was composed of the 
following: 
■ One 2.5m Cartsat-1 stereo pair collected over 
Mausanne les Alpilles on January 31, 2006 
(Path=0127, Row=0198), provided by ISRO (Figure 
i); 
■ A set of 32 high precision Ground Control Points 
(GCPs), provided by the Principal-Investigator (PI) 
European Commission-Joint Research Centre (EC- 
JRC). Figure 2 shows the GCPs distribution on the 
study area; 
■ A high-resolution DTM (ADS40 DTM) with 2m grid 
cell size and produced using a Leica ADS40 digital 
camera, provided by the PI EC-JRC (Figure 3).