DEM GENERATION FROM HIGH RESOLUTION MULTI-VIEW DATA PRODUCT 
B. Gopala Krishna*, Amitabh, T P Srinivasan, P K Srivastava 
Space Applications Centre, Indian Space Research Organisation, Ahmedabad -380 015 (ISRO), 
India-(amitabh, bgk, tps, pradeep)@sac.isro.gov.in 
Commission I, ThS-3 
KEY WORDS: digital elevation model, stereo image, accuracy, image matching, Cartosat-2 
ABSTRACT: 
High resolution space-bome remote sensing image data show a high level of detail and provide many opportunities to be integrated 
into remote sensing applications. In particular, surface mapping from multi-view and stereo data sets becomes feasible with height 
accuracy in the meter range. Cartosat-1 and Cartosat-2 are the two Indian satellites which provide the high resolution images. 
Cartosat-1 is a unique satellite having along track stereo imaging capability with 2.5 m resolution. Cartosat-2 is the second satellite in 
the Cartosat series which was launched during January 2007 by PSLV. Cartosat-2 is a high agility advanced satellite with a high 
spatial resolution of better than lm in panchromatic band with an operational life of 5 years. Cartosat-2 provides standard multiple 
scene product called as Multi-view with an overlap of more than 80 percent. Stereo image viewing has been the most common 
method of elevation modelling used by the mapping, photogrammetry, and remote sensing communities. Multi-view Image contains 
radiometrically corrected images with rational polynomial coefficients. Maximum three multi-view images are possible in a single 
pass of the satellite. In this study Multi-view Images have been treated as stereo image pairs to obtain stereoscopy. Generating DEMs 
from stereo data normally requires the use of a geometric model and ground control points (GCPs). The collection of GCPs presents 
a significant problem in many practical applications due to non availability of GCPs. A DEM generation method which requires no 
GCPs would therefore be of significant interest to users of stereo data. The RPC model was computed for each image. A pair of 
quasi-epipolar image is generated from the stereo images to retain elevation parallax in the X-direction. An automated image 
matching procedure is then used to produce the DEM. In this study, automatic DEM extraction of Cartosat-2 multi-View data 
without the use of GCPs has been evaluated, as well as the improvement of extracted DEM quality by applying horizontal shift on 
reference DEMs from the available Global DEMs or other source DEMs. High quality DEM has been generated at 2 m grid spacing 
which will be of immense use for producing digital city model (DCMs). 
1. INTRODUCTION 
High resolution space-bome remote sensing image data show a 
high level of detail and provide many opportunities to be 
integrated into remote sensing applications. In particular, 
surface mapping from multi-view and stereo data sets becomes 
feasible with height accuracy in the meter range. Cartosat-1 and 
Cartosat-2 are the two Indian satellites which provide the high 
resolution images. Cartosat-1 is a unique satellite having along 
track stereo imaging capability with 2.5 m resolution. Cartosat-2 
is the second satellite in the Cartosat series which was launched 
during January 2007 by PSLV. Cartosat-2 is a high agility 
advanced satellite with a high spatial resolution of better than 
lm in panchromatic band with an operational life of 5 years. 
Cartosat-2 provides standard multiple scene product called as 
multi-view with an overlap of more than 80 percent. Stereo 
image viewing has been the most common method of elevation 
modeling used by the mapping, photogrammetry, and remote 
sensing communities. In this mode of imaging, strips on either 
side of the track in the North-South or South-North direction are 
considered and one strip selected can be imaged maximum three 
times with different look angles with a specified strip length. 
Multi-view Image contains radiometrically corrected images 
with rational polynomial coefficients. Maximum three multi 
view images are possible in a single pass of the satellite. In this 
study Multi-View Images have been treated as stereo image 
pairs to obtain stereoscopy. 
Digital elevation models (DEM) are generated by traditional 
photogrammetry with aerial photos, by airborne laser scanning, 
with stereo images from space called stereogrammetry, or with 
interferometric synthetic aperture radar (InSAR) [Jacobsen, 
2004]. Stereogrammetry involves the extraction of elevation 
information from stereo overlapping images, typically airphotos, 
satellite imagery, or radar. To obtain stereoscopy with images 
from satellite scanners, two methods are possible: along-track 
stereoscopy from the same orbit, using fore and aft images, and 
across-track stereoscopy from two adjacent orbits. 
DEM gives the information about the shape of earth surface 
which can be used for various tasks like map creation, urban 
planning, flood control, resource management, 
telecommunication planning, military mapping etc. Elevation 
data, integrated with imagery is also used for generating 
perspective views, useful for tourism, route planning to 
optimize views for developments and to lessen visibility of 
forest clearcuts from major transportation routes. 
The manual method of DEM generation is a time consuming job, 
so the most of the data processing is done by automatic/semi 
automatic methods. With the help of remote sensing methods, 
one can generate DSM (Digital Surface model) which is the 
height on the earth surface over canopy cover (Vegetation & 
man made structures). The conversion of a DSM into a DEM is 
another task of research in remote sensing [Baltsavias, 1999]. 
In this study, we have examined the automatic DEM generation 
from Cartosat-2 multi-view images without the use of GCPs, as 
well as improvement of extracted DEMs using the Shuttle 
Radar Topographic Mission (SRTM) DEMs. Available data sets