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Integrated Remote Sensing and GIS for Natural Resources Management
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Asian applications of the 'WETNET' concept - A personal computer network to receive daily global satellite data sets and derived geophysical products
Once each day's worth of basic SSM/1 data, related geostationary, and other polar on biter data is assembled , a full set of global and swath data will be used to prepare numerous global browse images in various product formats such as precipitation rate and others listed earlier. Also, collective clouds through compositing for viewing frequently-obscured ground and coastal regions and to
evaluate them in terms of vegetation index and sea-surface temperature, respectively. We will also accumulate values of estimated precipitation amount , and average cloud liquid water and precipitately water to look for seasonal behaviour and variability that would help to set a base for consideration of climatic changes from current patterns.
There will be an optical disk sent to each scientist every month containing all of the daily data plus all of the derived products and the products prepared from the ancillary data. In this way we can evaluate the strengths and weaknesses of daily data transmission via electronic means compared to monthly dissemination of optical disks. The complete data record in the hands of each researcher also forms what is known as a distributed archive. This methods eliminates the need for future requests of retrospective data.
All of the networked scientists will receive the same personal computer system for the receipt and on-site processing of the SSM/I and related ancillary data. It consists of an IBM PS-2, Model 70 with a 120 Mbyte hard disk and 6 Mbytes of RAM. It will be provided with McIDAS image processing software and optical disk reader for archival access as well as a packet-switching modem for achieving wide data bandwidths and error-free data transmissions over conventional telephone lines. The software has been augmented to allow easy menu-driven data handling and mage processing. Even relatively computationally-intensive calculations such as remapping to different map projections can be done directly from menus. Also, strings, of frequently-used commands can be initiated with a single keystroke.
Automated receipt of daily data files will be achieved by having an internal software program place the computer in a ready-to-receive mode at a time early during each morning when the telephone lines are used least and when no one is likely to wish to use the PC workstation for research. When the scientist arrives for work each morning, he or she may trigger an automatic or manual scan of the received data.
Asian applications of a Wet Net Type of System
The advantages and disadvantages of such a system for the Asian community would seem to be as follows. The primary advantages of this technique is that for the selected problem and the agreed remote sensing data sources each participant receives all f the data. So no time or resources are wasted in the process of ordering desired data or data products . Each participants has a sample of all of the data so that he can instantly determine data voids and can use the estimated geophysical parameter maps as a gauge for the quality of the data. While the transmitted maps should not be held to absolute accuracies that would be acceptable in a court of law, they do givc3e an indication how the data channels would respond to the application of a particular estimation algorithm. For the greatest accuracies, a scientist would use the browse products to focus in on a particular data set, then analyze it extremely carefully with his personal computer system to insure that no inadvertent mistakes were made during the calibration, navigation, or channel co-registration stages. He might then also apply several slightly differing algorithms which might account for subtle
variations in the particular environmental conditions applicable to the specific scene.
Such a system could be used in a single laboratory setting where the analysts are working on the same problems or data sets, but possibility not all working in the same room or building. There, the idea of distributing machine-generated interpretations of routinely-obtained remote sensing data sets to all the persons working on detailed analyses would given the project a degree of standardization for all involved. in the case where the different coworkers are skilled in different scientific disciplines and may not each be experts in each other's remote sensing interpretation techniques, the browse products help to illustrate the varying analysis techniques and serve to provide a cross-training purpose.
When one considers such a data transmission system for a team of international scientists, the problems of implementation increase, but not because of a failure of the concept, rather because of the difficulties of reaching international agreements for the standardization of the hardware and software to be used, the analysis algorithm to be used, standard GIS data formats, and methods for effectively and economically using the international communication links. While these difficulties might seem formidable, the advantages of being able to see frequent maps of interpreted data would seem to make the effort worthwhile.
If one organization serves as a source of remote sensing imagery for others, this standardized method of providing a data browse image electronically in a GIS format could be an effective way of showing data coverage, quality, and likely interpretations before other data users would order specific high-resolution data. A nominal fee could be charged by the data source organization for the service and the imagery could be provided upon request rather than through routine scheduled distribution.
Conclusisssons
While a full Asian implementation of an international wetNet type of electronic browse image distribution might be prohibitive due to high recurring communications costs or difficulties in obtaining standardized or compatible hardware in various countries, the value of reviewing satellite image data over the same geographical area on a routine basis as well as related, computer-derived geophysical product maps from that data, would certainly seem to be a convenient way for scientists with different training and located apart from one another to study common environmental problems and to reach consensus conclusions on their causes.
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