A State mosaic ready referral system M.Nagamani, V. Subramanian, S. Rajendra Kumar, K.M.M. Rao National Remote Sensing Agency, Balanagar, Hyderabad 500-037, India. Keywords: Toposheet, Scale, Mosaic, Time composite Abstract: Remote sensing data is being used all over the world by different user community for resource development. This data forms a basis for study of various problems. User always looks for readily available resources with value addition as a basis for his work. At NRSA, value added products like geocoded products, user defined area extracted products, PAN sharpened products and mosaic products are being generated using different sensors data of IRS series satellites. As a part of product generation state mosaics of India are carried out under various projects. The products contain image data and vector layers like administrative boundaries of state & district, 1:250,000 topographical grid and state capitals & district head quarters. This type of products requires skilled manpower and time. Hence, all these mosaic products have been archived as a database along with scene details, which can be readily used. Browse images of this database along with vector layers were ported onto NRSA website with required web based software for users ready reference. This paper discusses about the design and development aspect of the web based ready referral system for browsing of state mosaic value added products and the GIS related features of the same. 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. Design & Development Aspects The software was developed using Java to make it platform independent and web based. This web based software with all support files occupies maximum of 4MB disk space. All the image files and Information files are stored in compressed mode and encrypted ASCII format respectively for better data security, disk space management and to make the software more compact and faster. Image files size is restricted to 400 X 400 X 3 pixels so that users with lower PC versions can also be able to use it. This Utility can be better accessed with Netscape Navigator version 4.5 and above. The boundary information provided in this software is extracted from SOI generated state and district boundaries and 1:1 Million SOI maps etc. By placing this utility in NRSA website we wish to make the NRSA user community aware of the value added services provided by NRSA and have a ready referral of the same with the use of internet. Apart from state mosaic visual images it also provides other facilities like Geographic, Topographic and IRS scene information based on the place selection. Optimal scene coverage of selected state can also be viewed based on online sensor selection. As it provides most of the geographic information it is treated as Internet based GIS facility. Operational Aspects Iinvoking this utility the web based window with India image and neccesary information and query items will be displayed (ref. Fig. 1). The image information such as mission details, period of the data acquisition and scale of the data archived are provided in the Scene information block. Iinformation like number of states and union terrerories and spread of DOS centres, RRSSC centres and State remote sensing centres are also shown in Country Information block. On selection of any of the centres the location of the same can be seen in the image. Mouse pointer info block provides 1: 1 Million toposheet Id with State name and Capital over valid Indian region. State of interest can be selected either by mouse click or from list box provided. The overlays avaliable at country level are shown in the overlays list box. Multiple overlay selection option is also provided. Based on selected overlays the same will be overlaid on the image(ref. Fig. 2). Prominent places of Indian region are listed in the places list. On selection of a place from the list box location of that place will be marked on the India mosaic and geographic information of the same is shown. Package information can be viewed in detailed by using Package Information button.
Fig 1 : Main menu Fig 2 : India Mosaic with overlays and Information
Once the state is selected state mosaic image of the same will be displayed along with required information and queries. Scene, State, Mouse Pointer information and Mouse Click information are shown in the left side column and the query boxes are provided in the right side column(ref. Fig. 3). State Capital and number of districts of the state, RRSSC centre availabililty and State remote sensing Centre are shown in State information block. On selection of capital, RRSSC or RS Centre the location of the same will be marked on the state image. Mouse movement provides 1:250,000 Toposheet Id with district name and Head quarters. Mouse Click provides Geographic coordinates, toposheet covered and selected IRS scene coverage of the mouse pointer position in Mouse Click Info block. Once the Mouse pointer is kept on the Head Quarter position, District and Head quarter names are shown in Mouse Pointer Info block. The overlays provided at state level are district boundaries, district head quarters and 1: 250,000 grid coverage. On selection all or some of the overlays can be seen over state image(ref. Fig. 4). Fig 3 : State Mosaic with District & Head Quarters Overlays
Fig 3 : State Mosaic with toposheet Grid & District Head Quarters Overlays More than one overlays provided can be selected from the list box. Using Place selection option places covered in the selected state can be listed and position of the selected place can be viewed on the state image. By clicking the mouse on the place position the geographic coordinates, toposheet covered and IRS scene coverage can also be viewed in Mouse Click Info block. On line help facility is also provided. Algorithms used: Inside & Outside Test: Inside and Outside test algorithm is used for the estimation of Scene coverage of a particular state. Transformation: Online geographic coordinate information was provided from the cursor coordinates using coordinate transformations like affine and perspective based on extent. Applications: This software has been extensively used in NRSA during the State Mosaic products generation for most of the Indian states from time to time. The database archived increased the throughput substantially. It can be accessed by the users through Internet and get most of the information of Indian region using various options provided. This software is being used effectively by applications scientists in their work estimation of various fields like land use, forestry, water resources management etc. Conclusion: The software can be used as tool in NSDI project where other product types like merged and WiFS data products were planned to be stored. This database created for this utility can be included in NSDI project. Whenever new states are formed database can be updated. Recent state formations like Uttanchal, Jarkhand and Chhattisgarh have also been updated. It can be further extended to District
mosaic products (using LISS-III data) based on users response. The satellites supported are all IRS series and LANDSAT-5-TM. The scene details provided are based on the referencing schemes of the satellites, which will be correct under ideal conditions of the orbital elements. However there may be minor variations due to day to day changes in orbital position of the satellite. References: Index Map and 1:1 Million scale state maps published by Survey of India. Digital Image warping by Dr. George Woolberg. Interactive Computer Graphics by Stevens. Handbook of IRS-1C published by NDC, NRSA. Acknowledgements: We are very much thankful to Dr. R. R. Navalgund, Director, NRSA for approval and encouragement in developing this package. Our sincere thanks go to Sri A.S. Manjunath, GD(SP & QE) & Mr. D.S. Jain, Head IS&SPD for their valuable suggestions as and when needed. Our special thanks goes to Mr. Y. Chandra Sekhar who provided software development support as and when required. We are thankful to Mr.Y.V.Suryanarayana and Mr.D.Srinivas of IS&SPD for providing administrative boundaries of the states and carrying out the internal software evaluation.