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ANALYSIS OF DEM GENERATED USING CARTOSAT-1 STEREO DATA 
OVER MAUSANNE LES ALPILES 
- CARTOSAT SCIENTIFIC APPRAISAL PROGRAMME (CSAP TS - 5) 
Y V N Krishna Murthÿ a , S Srinivasa Rao a , D.S. Prakasa Rao a , V. Jayaraman b 
a RRSSC/ISRO, Amravati Road, Nagpur, INDIA-440033 (yvnk, ssrao, dsprakash)@isro.gov.in 
b ISRO HQ, Bangalore - 500000 vjay@isro.gov.in 
Commission I, SS-11 
KEY WORDS: CARTOSAT-1, geometry, digital elevation model, errors, quality, RPC, Ortho-image 
ABSTRACT: 
The high-resolution Cartosat-1 stereo image data is expected to have significant impact in topographic mapping and watershed 
applications. The objective of the present investigation is to make an assessment of the potential of the Cartosat-1 data in topographic 
mapping and generation of DEMs in operational mode using COTS packages. The assessment is based on the entropy analysis of the 
fore/aft images, geometric quality of the fore/aft images (2-D perspective), generation of high-resolution Digital Elevation Model (DEM), 
Quality evaluation in different elevation strata, generation of ortho-image and associated accuracy assessment and application potential of 
the photogrammetric products for natural resources applications. The results of the study are part of phase I of C-SAP participation as a 
Co-Investigator (Col) in the evaluation of CARTOSAT-1 data for test site TS5 (Mausanne-les-Alpilles, France). The inherent orientation 
accuracy of the Rational Polynomial Coefficients (RPC) models is established by comparison to the available ground truth. Ground 
control points are used to correct the RPC (bias correction and also higher order transformations) in order to assess the achievable 
accuracy for the generation of digital surface models (DSM). The evaluation of the geometric accuracy is based on the estimated sensor 
model parameters and on the residuals at the image control and check points using various configurations of control points. The DEM 
evaluation is based on the elevation differences at control points, the spatial distribution of the DEM differences and terrain gradients. 
The ortho-image is evaluated with respect to available reference data. The potential of thematic content for Cartosat-1 for mapping 
applications is tested based on the detection and identification of various topographic features. The average entropy of the image is 
around 5.6. The standard deviation, of the CartoSAT-1 DEM in comparison with high quality reference DEM, is of the order of 3.8m to 
7.3m in different topographic conditions. 
1. INTRODUCTION 
1.1 Study Aim 
CARTOSAT-1 is designed for cartography applications. Satellite 
is placed in the polar Sun Synchronous Orbit of 618 km from 
Earth. CARTOSAT-1 has two high-resolution panchromatic 
sensors recording stereo images in the visible radiation. The 
recording swath is about 30 km with a spatial resolution of 2.5 m. 
The two sensors are acquiring stereo pairs from the same orbit. 
Images are obtained in fore/aft directions in near real time by the 
two sensors. The products of Cartosat are more useful in 
cartographic mapping and various GIS applications. 
The unique characteristics 
are given below. 
Spatial Resolution 
Radiometric Resolution 
Swath 
Product Dimensions 
Approximate Cost 
National Level DEM 
Planimetric Accuracy 
Vertical Accuracy 
Processing Tools 
of CartoSAT-1 and planned products 
- 2.5m 
- 1 Obits 
- 30km 
- 30km * 30km 
- ~ 1 USS/sq.km 
- CartoDEM 
- 15m (CEP90) 
- 8m (LE 90) 
-SAPHIRE 1.0 
- SST/ASST 
- COTS Tools 
The study objectives are: 
• to analyse 2-D Geometry of Cartosat-1 stereo pairs 
• to analyse Radiometry of Cartosat-1 stereo pairs 
• to generate DEM from Cartosat-1 stereo pairs 
• to analyse DEM wrt Reference DEM 
• to generate Ortho-images using Cartosat-1 derived 
DEM 
• to analyse Positional Accuracy of Ortho-images 
1.2 Study Area 
(Test site 5 - Mausanne-les-Alpilles): The spatial extent of the 
study area is 4d 39’ 47.16” to 5d 06’ 55.29” East longitude and 
43d 39’ 22.90” to 43d 50’ 12.40” North latitude, falling in UTM 
31 zone. 
The study site is located near to Mausanne-les-Alpilles (France) 
(Figure 1) and presents a low mountain terrain with elevation up 
to around 650m above mean sea level, mostly covered by forest, 
surrounded by low-lying agricultural plains. A number of small