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A State mosaic ready referral system


M Nagamani
National Remote Sensing Agency, Dept. of Space, Balanagar, Hyderabad, 500 037


V Subramanian
National Remote Sensing Agency, Dept. of Space, Balanagar, Hyderabad, 500 037


S Rajendra Kumar
HSPDS, DPA, NRSA, Balanagar, Hyderabad, 500037
Email: rajendrakumar_s@nrsa.gov.in
Fax : 040-3879307
Phone No. 040-3884417


Dr K M M Rao
National Remote Sensing Agency, Dept. of Space, Balanagar, Hyderabad, 500 037

Introduction:
India, over the past years, produced a rich base of map information through systematic topographic, geological, soil and cadastral surveys, various natural resources inventory programs and use of Remote Sensing images. Further, with the availability of precision, high resolution satellite imagery, data enabling the organization of GIS, combined information being aquired with the Global Positioning System, the accuracy and information content of these spatial data sets or maps is extremely high. Users require data that can be readily used to start their job.

National Remote Sensing Agency has steadily improved from the launch of IRS-1A to till date in the quality and quantity of products supplied with improved spatial and spectral information data and providing training and conducting workshops to the users to improve users awareness regarding new products. Launch of IRS series satellites has provided multi sensor data acquisition capability which in turn has enabled NRSA to provide data at a faster rate and with better accuracy & frequency. Now NRSA has a huge archives of satellite imagery collected during last three decades. Basically the data being supplied is based on satellite referencing scheme (ie. With path / row details) in most of the cases. If the user interested area is toposheet based or part of toposheet or larger than the scene then additions efforts are to be put in generation of such products. In such cases it is often necessary to do mosaic of more than two scenes to cover entire user required area. Additional information like annotation overlay, vectors overlay and geographic grids overlay are to be provided. The products generated in this special chain are termed as value added products.

With the advent launch of IRS-1C/1D with high resolution, high revisit capability, demand for mosaic products of larger areas like district, state and country mosaic products using LISS-III and WiFS sensor data started in Natural resources development such as Agriculture, Forestry, Water bodies etc. The demand for such products has been increasing. These large area mosaic products are useful for viewing the synoptic view, continuation of geographical features, broad estimation of resources and planning & monitoring of resource projects. State mosaic products of most of the states were generated under various projects like integrated resource management, forestry and geosciences etc. The task of these mosaic products preparation involves handling of voluminous data radiometry balancing, geometric correction of images and geocoding the mosaic data. Generally country, state or district mosaic product genration follows by the steps given below.

• Selection of satellite data with sufficient overlap
• Verification of images for Band to Band Misregistration
• Identification of control points between images.
• Histogram matching and blending between images to get seamless output.
• Seamless mosaic image generation using common area and control points.
• Georeferening the image to the required scale of map.
• Overlaying vector layers like mandal/district/state boundaries and annotation layers.

As the time composite mosaic preparation involves problems like handling voluminous data and radiometric and geometric parameters adjustment based on the duration of the data acquisition it requires skilled manpower and time. Hence, all these mosaic products that are generated under various projects during different times are populated as a database along with scene details and corresponding vector and annotation layers. This database can be used as reference for future products generation without repeating time taking processes like vector & annotation layers creation, data geocoding etc. With this database State Mosaic products can be generated at a faster rate, as most of the work is readily available. The browse images of this database along with vector layers were ported onto NRSA website with required web based software for ready reference. User can check for usefulness of this data with respect to state of interest and date of acquisition. If he is satisfied with the data he can directly order for the same. Otherwise he can order for recent dates. In that case image data can be replaced by recent dates data and based on user requirements any other vector or annotation layers can be added.