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An application system and its intelligence for earth resource satellite

Chen Shupeng Li Zhirong
Chinese Academy of Sciences

Wang Yuan
Chinese Academy of Space Technology


Abstract
An application system is proposed for the Earth Resource Satellite (ERS) project. The system under consideration consists of five subsystems:
  • The data receiving and recording subsystems;

  • The data preprocessing and production subsystems;

  • The applied analysis and specialist subsystem (AAS);

  • The data simulation and evaluation subsystem;

  • The data distribution and user's service subsystem.
Except the traditionally satellite receiving and preprocessing subsystem, the important subsystem of AAS will be discussed in detail. It is basically geographic information of remote sensing imagery.

Such a subsystem will provide the real time and effective dynamic data information to various users for different economic constructions. It is also able to supply the global static information and thematic map of a certain part of the country or even the whole country.

Earth resource satellite (ERS) needs an application system
Since the first American ERST satellite was successfully launched in 1972, its data was used in more than 150 countries and its social and economical benefits were quire obvious. Btu the use of satellite data for remote sensing applications in different countries were separated and less concerned for whole country wide, so the results of applications only solved some regional problems. if we want to make the most of ERS works, a complete application system should be considered. This application system is also one of the five parts of the whole satellite engineering. The other four parts are satellite, rocket, control and communication and launching field. The relations between then are shown in Figure 1. As an application system, it has the capability to research renewal resources in an large area and dynamic monitor the environment.


Fig. 1 Earth Resource Satellite and Applications System

In the future, the application system of ERS can provide global thematic maps or statistics with practical values for national planning or decision making.

For operational process, the auxiliary data will be input to the system at different stages and the system also output different products at different stages to satisfy the demanding of different uses. Fig.2 shows the flowchart.


Fig. 2 Information flowchart of application system and It's feedback

The conception design and technical bases of subsystems
  1. Receiving and preprocessing subsystems

    This systems is the data source of the whole application system. It undertakes the data receiving, recording, radiometric and system geometric corrections, and the standard films and computer compatible tapes (CCT) productions. The subsystem should be an operational system and has the capability of mass production for the requirement of dynamic monitor.

    To cover the land and sea of whole country in a period of 1-2 years and renew the environment data and maps of renewable resource require high through out of ground station. For example, the total landarea of China is 9.6*106 Km2. It needs 85 international map sheets for whole territory and 65 sheets for land areas. So far the standard products of ground station are generating geocoded imagery which is which is mission-independent geocoded remote sensing products and involves projection onto a fixed and suitable common cartographic projection.

    The geocoded image products are based on map sheet and easy to use with existing map referenced data.

    Neither the high throughput nor the format change of products are more higher requirements to the data processing of future ground station.

  2. Applied analysis subsystem:

    This is an important subsystems in the application system. The products from the preprocessing subsystem will be processed and transformed to useful thematic maps and statistics information in this subsystem. The effectiveness of satellite data will be checked in this subsystem also. In order to output different maps and make decision quickly, the subsystem not only has powerful processing capability but also combine the specialist knowledge an human intelligence to realize high precise quantitative analysis and systematic intelligence.

    The total subsystem consists of four parts:

    • Digital image processing,

    • Geographical information system

    • Applied analysis model, (discussed in next articles)

    • Computer aided mapping

    Fig 3 illustrates the diagram of the subsystem.

    1. Image processing

      The image processing will comprise two aspects. One is general image processing which includes contract enhancement, edge detection, statistical calculation, information extraction and image classification. The other aspect is using the digital terrain model (DTM) or ground control points to do the high precise geometrical correction, large scale mosaic, graphic data handling, and the map output through the plotter.

      Special attention should be paid to the equipments of digitized graphic input and thematic map output.


      Fig3. Information Flowchart of Application System

    2. Geographical information system (GIS) and computer thematic mapping

      The new trend in the remote sensing field is the development of the image processing system with GIS. In the past years, the image processing system and GIs system have developed independently and parallels. An important problem to be solved for final convergence of two systems is the interface between these two systems.

      The main purpose of the GIS is to compensate the shortage of information in the Earth resource satellite application system. The data contents of GIS can be divided into two types:

      1. Graphic data base, databases

        It consists of map database, Digital terrain model and Database of place.

      2. Statistics data base : this data base had the items of space coordinate on time sequence. There are:

        Geophysical field, earth surface observation, natural environment base and social economic base. From the software point of view, the main question is the management system of spatial database and the correspondence relational and geometrical data base.

      The special software for GIS, compared with generation image processing, has a lot of graphic processing functions. It will consists of following items:

      1. Digitization of graphic and map: The determination of the value and direction of the graphic, the digitization of the point, lien and polygon etc…

      2. Graphical edition: Processing of the cross point, joint lines between the gap of two lines, registration and linking of different graphical files, converting the data format between raster data and vector data.

      3. Graphic processing: Curve spline, putting the value on the isopleth and 3-dimension display.

      4. Graphic output: Class: field map, isopleth map, statistics map, symbol and annotation….


      Due to a large amount of information in each map sheet, it requires large output size of he map, say 14000 * 800mm

      Besides, different thematic maps have different map scale. All of these need a high throughput of the CAC system.

      The relations between image processing, GIS, and CC are shown fig. 4.

  3. The data simulation and evaluation subsystem:

    This subsystem undertakes the data simulation experiment before and later the launching satellite, such as:

    1. Pre-launching airborne data simulation research, it will include the selection and modification of spectral band of earth resource satellite.

    2. Check the availability of the simulated sensors in the applications of the crops forecasting, landuse, geologic exploration and water survey.

    3. Post-launching evaluation f the technical specification of the satellite. It will include the accuracy of geometry, ground resolution, and radiometric calibration of sensors.

  4. Data distribution ad user's service subsystems:

    The products of application system it will be supplied to whole world. So it not only need a daily distributive system, but also asks to organize special symposium, publishing bulletin and introducing the experiments of products application to the users.

    The subsystem could register and log the processed image to build a directory of acquired imagery and link it to archive inventory. The quick look ask copy of received image are provided in this subsystem also.
The intelligence of application system
It is well known that the interpretation of remote sensing imagery by specialist knowledge is much better than the automatic classification by using most advanced computers. The image processing system in combination with GIS will increase the accuracy of the classifications other than only spectral information in common image processing system. If this system incorporation with specialist knowledges (i.e. human intelligence), the advantages of this new system are quire evident. The major superiority of the new system over the common image processing and GIS is its incorporation with human brain in the process of image interpretation or classification. Due to using the human intelligence in pattern recognition and applied analytic model, many practical problems in the economic construction can be solved more quickly and accurately. Fig. 5


Fig. 5 Method and Symbol of Image processing

  1. Contents of Intelligence in the application system

    To establish different analysis model and softwares by the specialist knowledge are important task in the application system's intelligence. This will promote the system to a expert system and intelligent machine.

    As for the analysis mode's it should include following six areas:

    1. Renew the national basic topographic map and data base of GIS; (1:250,000 - 1,200,000) scale)

    2. Monitor land resource; (desertification, urbanization etc)

    3. Qualitative evaluation and estimation of water resources;

    4. Estimation products of main crops for large area; (wheat, rice, cotton…)

    5. Monitor of the flood, drought and other disaster in a large area;

    6. Geological mapping and exploration of the mineral resources in different regions.

    Beside the analytic model, the intelligences of image and graph processing are necessary, such as map, digitizing interpretation.

  2. The technical methods for establishing applied analytic model.

    1. First review and evaluate the works of former analytic and software system:

    2. Establish the digital formula and the procedures of logical inference

    3. Digital analog that combine with the physical model and practical conditions

    4. Design the software package that reflect the difference between each district area and introduce the real corrective coefficients

    5. Design each special intelligent machine.

    The concept of the classifiable machine should add to the above procedures. Several special analytic knowledge databases are needed to enhance the man machine interaction. The fuzzy mathematics and pattern reorganization are used to perfect the logical interference model. See Fig 6.
Conclusion

  1. The Earth resource satellite has developed more than 20 years. S for sensors and platform of satellite also got much progress. But the information processing and the applications of satellite data lagged behind others in the whole Earth Resource satellite system. In order to raise the application's level, it should have a general plan to establish an operational system that combines the information processing, analytic model, GIS, and user's service as a whole.

  2. Due to the mass volume of the data in application system, the processing speed must be quick and fast. In the application side, it needs to solve the practical problems and qualitative analysis. All of these require high qualitative products and system's intelligence. Then the operational application system had the capability to solve the practical problems such as the real time monitor of landuse or disaster for whole national wide.

  3. The intelligence of application system includes many sciences, such as space science, information science, geo-sciences and bio-sciences. It also interacts each other among the computer, remote sensing, information processing, and automation. So the development of the intelligence of the system will open the new areas of the high technology.
References
  1. Wang Da-Heng & Pan Hou-Ren, Acad. Sinica, Presented at ISY SAFISY Conference, UK Feb. 1989.

  2. Chen Shu-Peng, Presented tot eh ISY SAFISY conference, UK. Feb. 1989

  3. Chen Shu-Peng, Selection from the bulletin of the Chinese Academy of Sciences, 3, 1987 47-53.