SYNTHESIS OF INVESTIGATIONS UNDER ISPRS-ISRO CARTOSAT-1 SCIENTIFIC 
ASSESSMENT PROGRAMME PRIMARILY FOR DSM GENERATION 
R. Nandakumar 3 , Amitabh, MPT Chamy, Satya Soma Sekhar Kopparthi, Gurudev Paswan, Shilpa Prakash & 
Sanjay Singh 
Signal & Image Processing Area, Space Applications Centre, 
Indian Space Research Organisation, Department of Space, Ahmedabad - 380 015, India - 
(nandakumar, amitabh, mptchamy, sekhark, paswan, pshilpa, sks)@sac.isro.gov.in 
Commissioni, SS-11 CARTOSAT-SAP 
KEYWORDS: Cartosat-1, DSM generation, DSM Quality Assessment, Orthoimage, Feature extraction, Topographic mapping 
ABSTRACT: 
Cartosat-1 with two identical optical sensors Fore & Aft operating in panchromatic band to operationally acquire along-track stereo 
images (or wide-swath mono images) was launched by the Indian Space Research Organisation (ISRO) from the Satish Dhawan 
Space Centre, Sriharikota on May 05, 2005. ISPRS-ISRO Cartosat-1 Scientific Assessment Programme (C-SAP) was initiated with 
an announcement of opportunity on January 13, 2006, through an e-mail and a web-page announcement in Commission-IV website 
for evaluating the mapping potential of Cartosat-1 stereo data. A number of test sites and investigators spread across the globe were 
selected for this Programme by an international evaluation team. Principal Investigators provided reference data sets over the test 
sites for which Cartosat-1 stereo orthokit data products were provided by ISRO. The results of these investigations by not less than 
14 independent teams on at most 11 test sites using a variety of in-house-generated and commercial photogrammetric processing 
software, with data acquired by Cartosat-1 during different seasons of the year have been presented in (a) Commission-IV 
Symposium at Goa in Sep. 2006, (b) Inter-Commission Workshop held at Hannover in 2007 and (c) currently at Beijing in July 2008. 
While these investigations cover (1) stereo triangulations with one or two overlapping stereo pairs for sensor orientation and 3D- 
geo-positioning, (2) stereo image matching, space intersection and interpolation to generate a regular grid of Digital Surface Model 
(DSM), (3) orthoimage generation using either of the Fore or Aft sensor data sets, (4) feature extraction & (5) topographic mapping; 
along with evaluations at each step with reference data sets of higher (or comparable) quality, this Paper is an attempt to synthesise 
all the results of these investigations to draw conclusions on the overall capabilities of Cartosat-1, with primary emphasis placed on 
DSM generation. The conclusions include: Employing a few externally measured and precisely transferred ground control points, 
Cartosat-1 stereo pairs could be successfully used (1) to generate DSMs with 5 m grid posting in rolling plains; (2) to generate 
DSMs with 10 m grid posting in all other types of terrains (including hilly) with an accuracy of 0.5 pixel in planimetry and 1-2 pixels 
(la ) in height; (3) to generate orthoimages with sub-pixel accuracy; and (4) to generate topographic base maps in 1:10,000 scale. 
The capability of Cartosat-1 image data sets are superior to ALOS-PRISM, SPOT-HRS, IKONOS or QuickBird particularly to 
generate DSMs, in the light of their 10-bit radiometry with a wider panchromatic band, optimal stereo angles for better stereo image 
matching and operational along-track stereo acquisition. 
1. INTRODUCTION 
This Paper discusses the results and compiles the conclusions of 
independent investigations on Cartosat-1 stereo pairs carried out 
by not less than 14 specially chosen teams on at most 11 test 
sites spread across the world using a variety of in-house- 
generated or commercial photogrammetric processing software, 
with data acquired during different seasons. The investigations 
included evaluation of results using higher (or comparable) 
quality reference data sets. The results have been mainly 
presented during (a) Commission-IV Symposium at Goa in Sep. 
2006, (b) Inter-Commission Workshop held at Hannover in 
2007 and (c) currently at Beijing in July 2008. Several 
investigators had provided their final reports either with or 
without their full Papers submitted to the Beijing Congress to 
the C-SAP secretariat for this Study. 
1.1 CARTOSAT-1 Mission and Fore & Aft 
Instruments: 
Cartosat-1, one of the optical Indian remote sensing satellites, 
was launched on May 5, 2005 by ISRO from the Satish Dhawan 
Space Centre at Sriharikota. It has two identical and 
independent PAN sensors, Fore and Aft, having a resolution of 
2.5 m acquiring images in stereo mode for the production of 
digital terrain models as well as in wide-swath mode for the 
production of mono image mosaics. 
The Fore and Aft cameras are inclined fore-ward and aft-ward 
by + 26° and - 5° along the ground track, giving a base-to-height 
ratio of 0.62. These instruments operate in the panchromatic 
band with 10-bit radiometry and a swath of 27.5 km each. 
During imaging, the spacecraft is maneuvered continuously so 
as to acquire either stereo or wide-swath images. This 
maneuvering could be realised throughout the length of the pass 
for a given ground station or as per desired duration. 
The stereo imaging provisions of the spacecraft include options 
to be tilted in either the pitch direction to acquire additional 
stereo images with - 26° and + 5° or symmetrically with ± 15.5° 
or in roll direction to cover specific areas with a reduced revisit 
period. More details on the Cartosat-1 mission and the sensors 
could be seen in Srivastava et al., 2006.