Indian Remote Sensing Satellite Cartosat-1: Technical features and data products


  1. Triangulated Control Points Library Generation (TCG):
    To enable scene based precision processing for mono or stereo mode data acquisition, a second generation control points call TCP of approximately about 10 points in each standard scene (~30 x 30 KM) covering the entire region are generated and maintained as a data base and are used during products generation.


  2. Data Product Accuracy:
    The accuracy of various products planned to be generated depends upon the accuracies of the SST parameters, TCDS, Coarse DEM, Precision DEMs etc. It is planned to have SST parameters within an accuracy of 3.3 M (1s) based on GCP coordinate of 3M in planimetry and height accuracies. The accuracy of TCP derived from the SST processing is about 4M (1s ) and based on conjugate point identification accuracy of about 2.5 m (3s). The Coarse DEM will have planimetric error of about 3.1 (1s ) equivalent to the SST parameter error and the height is depending on the planimetric error and N/H ratio. The final DEM is generated after incorporating break lines / break points through manual / semi automatic methods with an RSS error of 2.5 m (1s) in planimetry and 3.1 m in height.

    The error budget calculated for scene level processing is for a scene size of about 30 KM x 30 KM and less and is of the order of 0.25 m (3s).

    The location accuracy of various data products are given below:
    1. For system level correction (level 1) (3s) : 220 m
    2. With GCP (level 2) (3s ) : 18.7 m
    3. With terrain (Coarse DEM) corrected (level 3A) (3s): 21 m
    4. With final DEM (LEVEL 3B) (3s) : 18.7 m
    5. With precision GCP & precision DEM (level 3C) : 6.4 m* (3s)

    *This product uses precise GCPS and precision DEM with incorporation of break lines and break points. Hence the internal distortion will be better than 1 pixel (<2.5 m). The level 2, 3A and 3B products are standard products whereas the level 3C products are always value added products whose turn-around time depends on the availability of the images and ancillary information (GCPs) etc.


  3. Data Product Size, Scale and Datum:
    Various Products size is (1) based on modes of operation vise mono, stereo or wide swath mode as defined by path/row or Lat./Long. referencing schemes, (2) User defined rectangular areas aligned to true North of minimum size 2.5 KM x 2.5 KM and area equivalent to the maximum scene size 30 KM x 30 KM, (3) User defined polygonal areas of minimum size 2.5 KM x 2.5 KM and (4) Standard Map sheet extents for 1:25,000 and 1:50,000 scales. All levels of products are oriented towards true North and standard map projection as applicable for different user needs across the globe. Also the horizontal and vertical datum of the geo corrected products is referenced to appropriate datum as applicable for different needs across the globe.


  4. Data Products Format:
    The digital products are generated and supplied in any conventional format like CEOS super structure and IRS fast formats with Cartosat specific changes, along with all necessary ancillary parameters addressing all possible data utilization needs of Cartosat-1 PAN data, for various levels of products for different application along with GIS and CAD and 3D software packages. The formats currently used in different GIS and CAD software packages such as Multi-Resolution Seamless Image Database (MRSID) universal data formats and Geotiff are suitably modified for Cartosat-I specific features.
Conclusion:
Several countries, apart from India have embarked on space based remote sensing. A number of remote sensing satellites launched in the last decade such as Landsat, SPOT, ERS, and IRS series have shown very encouraging results for variety of Land and Marine applications. They also have aggressive plans for advancing the remote sensing technologies for different applications in future. In India ISRO has taken a lead in Land Resource application Satellites and has evolved plans to sustain and advance in all areas of earth resource applications. Basically, Indian Space Programme in the Remote Sensing area plans for improved mission in the area of (a) Cartographic and Mapping Applications (b) Land and Agricultural applications (3) Oceanographic applications, (4) Atmospheric Applications and (5) Climatic applications. Although globally there have been many satellite system being operational and planned with higher resolutions to meet the ultimate information requirements of the user community for geo-engineering applications and cadastral requirements, the launch of Cartosat-1 is expected to meet the immediate demands for terrain visualisation, updation of topographic maps, generation of National topographic data base and other utilities planning.

Acknowledgement:
The authors are extremely thankful to Dr. K. Kasturirangan, Chairman, ISRO / Secretary DOS and Dr. P.S. Goel, Director, ISAC, Bangalore and Dr. A.K.S. Gopalan, Director, SAC, Ahmedabad for their constant encouragement in this Project. Authors also thank Dr. V. Jayaraman, Director, EOS, Sri. Sunder Ramaiah, Scientific Secretary, DOS for their useful suggestion and comments. The authors acknowledge the contributions from Dr. Ram Rattan, Dr. K.L. Majumdar, Shri A.S. Kirankumar, Dr. P.K. Srinivastava, SAC, Ahmedabad for the useful discussion held with them.

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