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The development and application of the kernel software of Microcomputer Geo-graphic Infomation System (MIGIS)

Wang Zhenwu, Wang Liang, Tang Xinming, Yang Jun
Research Institute of Surveying and mapping beijing, China


Abstract
This paper advances the basic idea of developing a kernel software of micro computer geographic information system to which the specific module for various specialities can be attached, and introduces the kernel software of MIGIS (Micro -GIS) developed by the end of 1988 by the Research Institute of Surveying and Mapping. The system design, system design, system structure and basic functions of each model will be given. It also gives a brief introduction to the practical system - Landuse Analysis and management System (LAMS), developed by the institute based on MIGIS.

MIGIS has outstanding characteristics, e.g. simple in graphic preprocessing, flexible in data inputing and editing, automatically setting up topology and searching errors, and standard map symbol base as well as marginal decoration , and easy to retrieve, update and maintenance , etc.

Introduction
Geographic information system (GIS) is a computerized system which can store, manipulate and analyse both spatial data and the attributes associated with it. In recent years, with the increasingly raising of the microcomputer performance/ price ration and development of all discipline fields microcomputer information systems especially the thematic information systems oriented to certain discipline are welcomed by users increasingly. Therefore, it is necessary to develop a microcomputer general GIS kernel system which can be taken as the kernel and basic of a thematic information system, then, combine and utilize the subject research , enrich and develop continuously the specific module which is available for different specialties.

MIGIS (MICRO GIS) is just developed on the basis of this idea. Meanwhile, the first specific information system, landuse analysis and management system(LAMS) taken MIGIS as kernel was developed by the end of 1988. The purpose of this system is to coordinate the national lansuse investigation, and complete office mapping, area measurement and establish landuse data base at county level in the investigation work. The system has been or trial in aprt of intended areas. The paper will indicate the basic design principle, structure and performance feature of MIGIS, a brief introduction will be made on several specific modules of landuse analysis and management system.

System environment of MIGIS

Host Computer : IBM PC/AT or its compatible computer
Internal Storage : one Mbyte or above
Hard Disk : 30 Mbyte or above
Floppy : 1.2 Mbyte (360 Kbyte aletrnative)
Communication Port : one parallel one serial or one parallel two serial
Display : high resolution (640 350 ) color graphic display
Display Card : EGA card
Digitizer : A1 format , 16 key
Plotter : A1 format
Printer : 24 pin line printer
Operation System : DOS above 3.0
Chinese Character : CC-DOS or Chinese card

The structure and function of MIGIS
  1. The Logical and physical Structure of MIGIS Design
    MIGIS uses "C Language +Assembling+dBASEIII" programming language . In the design of MIGIS, the design principle of module from top to bottom was adopted ; a full consideration was given to the microcomputer storage capacity and processing speed and program code length was compressed by optimization method. As a kernel software of general microcomputer information system, MIGIS includes the function of data input, interactive editing, setting up topology structure, a data base management , data base update, spatial analysis and mapping as well as report output etc. and preserves all kinds of specific module interface and user application program interface, its logic structure design as illustrated in Fig. 1.


    Fig. 1. The logic structure of MIGIS


    MIGIS stores spatial data by vector data format, stores attribute data or statistical data by dBASE file format ,organizes and manages data file by "directory file" One sheet of digitized map takes as a directory file" One sheet of digitized map takes as a directory. MIGIS sets up its internal file automatically on need . In order to save space and "directory file" one sheet of digitized map takes as a rectry and MIGIS sets up its internal file automatically on need. In order to save space and improve data safty and protection, most of the files are stored in binary form.

  2. The Basic Function of each Module of MIGIS

    1. Data input and editing
      Apply to digitize map, contours, air-photo map (provide for orthorectification) and graphic editing

    2. Othoroectification
      By use of digitial elevation model (DEM), to conduct orthorectification on air-photo, its coordinate will be tranfered into geodetic coordinate under Gauss projection.

    3. Set up and check of topology structure
      Set up and check of topology structure module is one of the main module of MIGIS. It uses the parameters given by user to complete automatic editing, arcs intersecting and splitting, nodes parameters given by user to complete automatic editing, arcs intersecting and splitting, nodes generating, node matching and according to the positioning relationship of points , arcs and automatically generate polygons, set up topology related listing file of relation feature. When topology is set up, the error information can be given in the system, and the graphic display and check plot hard copies can be given, so as to easily check and amend.

    4. The management of statistical data
      MIGIS selected dBASE III as statistical data base management system, it mainly apply to statistical data (including attribute data) input, amentment, management, maintenance, retrieve, etc. Under MIGIS, dBASE sub-directory is set up, which has all the original functions of dBASEIII, and realizes the inter-connection of spatial data base with statistical data base.

    5. Area measurement
      MIGIS can perform Length and area measurement. Meanwhile, the specific are measurement function needed by LAMS was increased in the specific module. It is the area measurement, Adjustment on each patch is carried out, line feature area, the scattered objects area, the scattered objects area less than graphic size and scattered small details area will be deducted automatically.

    6. Graphical retrieval and display
      MIGIS can realize certain graphic retrieval on map which has already set up topology structure. Its retrieval result forms a subset to original map and a new map can be generated. Therefore the retrieval result can realize any operation of the system.

      MIGIS provides graphic display function to any map or certain subset. User can check the space distribution and interrelation.

    7. The generating of digital elevation model (DEM) and terrain analysis MIGIS takes contours plus elevation points as data source to set up digital elevation model. Considering the processing capacity and speed of microcomputers, MIGIS only calls for the user to digitize relief characteristic points and elevation points on index contour to increase digitizing working efficiency and save storage space. When the point redundant on contours considered in the system is too large, the redundant points will be deleted automatically, thus raising the system running efficiency under the prerequisite to guarantee accuracy.

      Moreover, on the user requirement, the system will generate automatically slope map, aspect map, hill-shading map, three-dimensional map, etc. from DEM.

    8. Map output and report printing
      MIGIS developed mapping symbol base and marginal decoration software, its symbol base includes both topographic map general symbols and landuse map standard symbols. They can be used to draw various line features and patch symbols, and to adjust symbol scale and the distance of area symbol. For outside map decoration, it calls for user to input map number, the system will calculate and draw out standard outside decoration automatically.

      Furthermore, the system can also do the calculation and report output.
The characteristics of MIGIS system
In recent years, with the steadily expanding of microcomputer market, quite a few general or spatial space information system software of microcomputer supported was developed on internal market, which shows unquestional superiority relative to conventional operations. But as result of a lot of causes in system design that made graphic preprocessing, data digitizing and editing became another kind of hard manual labour and finally made many users step back. A lot of software only become " Demonstation System" and hard to enter into utility stage.

The problem of "utilization" was paid fully attention to in the system design process of MIGIS . The manual labour in the whole process working was reduced to a minimum so that it is easy to learn and master this system to reduce operator's intense and fatigue in all stages of working, to set up good friendly interface --- this is the goal that system designed and already achieved. It's main characteristics are:
  1. Simple Graphic Preprocessing Work
    It is unnecessary for user to identify digitizing direction, right polygon code, left polygon code, arc code etc. It only needs to encode line features and polygon inner point (used for assigning attributes, e.g. road, railway, boundary, rice field, arid land, etc.) thus reducing large quantity of identification, coding and attribute data input.

  2. Light Data Collection Mode
    user needn't to pay close attention to the direction and nodes during are digitizing, and just trace are as its convenient, and monitor on real time from graphic terminal, while digitizing, editing and checking also can be done. All the operations are defined by digitizer cursor key. In different modes, the definition of function key is given by monitor, thus reducing greatly the operator's intense and fatigue.

  3. Friendly interface Editing System
    In the digitizing and editing, functions of adding and deleting points and lines moving nodes and window defining are offered by MIGIS

  4. Automatically Setting Up and Checking Topology
    Arcs intersecting, nodes generating, spliting arcs, setting-up the topology of points, arcs and polygons can be completed by MIGIS, and automatic editing can also be done.

  5. Checking and Outputing Error Information
    The topology errors listing of a map can be given automatically after topology set up by MIGIS and it can identify arcs, nodes, inner points related which error information generate agraphic file, it is convenient for operator to check and amendment by terminal display or hard copy. Besides "Local Clean and Total Build" can be combined, it can raise working efficiency in the complex map operation.

  6. Connection With Spatial Data and statistical Data
    It can be convenient for the data data management, retrieval , updating and maintenance.

  7. Automatic Mapping and Report Printing

  8. Data Sources
    Data sources can be either maps or photo maps and the system can complete the automatic or thorectification itself.
Trial production and system testing
For the first specific information system ----the landuse and management system developed taken MIGIS as kernel, we selected successfully two test areas to carry out the trial production and testing.
  1. Field topographic map identification data used as data source. The whole processing from in put to output and special area measurement for 88 sheets of 1:0000 land use map of Kuitun city in Xinjiang have been completed. The characteristics of land use information in this city are large patch area, unitary land attribute, grass taken as the main part, a great difference among the densely distributed linear objects, various objects n high dense area e.g. canal, road , dry ditch, forest belt etc. are interweaved with each other, which constitutes a complex graph, so that increases the difficulty for input and data base building . Meanwhile, the data source of this region is topographic map which is field investigation plate, In terms of the above characteristics, the patch plate and the linear objects plate of a map will be digitized separately. Polygon to topology structure will be established. On patch plate, then the linear objects plate will be superimposed on to the patch plate, which realized the separation of linear objects and soace positioning within patch, so that linear objects can be taken as suspend arc section of patch. In the process of area measurement, it needs to deduct its area from the patch that it belongs to, and a measurement will be established. On patch plate, then the linear objects plate will be superimposed on to the patch plate, which realized the separation of linear objects and soace positioning with in patch, so that linear objects can be taken as suspend arc section of patch. In the process of area measurement, it needs to deduct its area from the patch that it belongs to, and a measurement will be carried out on a boundary that not constituted a patch. Such processing is on account of that there is a great relation between topology structure establishing and patch graphic complexity. The more the patch, the longer the topology structure establishing, thus the space on disk will be increased correspondingly. On the contrary, the time and space of topology structure establishing will be decreased, but is in great proportion to the whole system. As a result of separation plate processing, it reduced system operation time and improved working efficiency. During graphic output, the patch on grass is large, therefore, the interval of grass symbol is extended onetime, which achieves a good result. As compared with tradition method, the working officiency for LAMS can be raised 5-10 times . Taking a more complicated map as an example 4 person/month processing including air photo orthorectification and photos append by traditional method and 10-15 person/day by LAMS. and clip for 12 sheets of 1:10000 map of Shangrao in jiangxi involved in jiangxi involved 55 airphotos have been completed.

  2. Field air-photo identification data used as data source. The whole processing including air-photo orthorectification and photos append and clip for 12 sheets of 1:10000 map of Shangrao in Jiang-xi involved 55 airphotos have been completed. The land investigation using air photo as data source should carry out orthorectification first, then conduct area measurement: Shangrao area in Jiang-xi Province is port of hilly area, many kinds of land, complicated patch shape, high dence for water and road network, so the linear objects are densely located, and the curvature of arc section is large. To LAMS, land boundary and linear objects will be digitized on air photo first, then orthorectification will be automatically carried out with DEM of this region and appending, data base building, area measurement and result output will be completed automatically. For user, graphic input is only once, thus it avoid the two similar process of platting and finding the product by multiplication along arc section in the two processes of orthorectification and area measurement traditional method which greatly improved the efficiency and measuring accuracy slop map can be generated by DEM of this area, then superimposed with landuse map, the slope of farm land under 25 deg. and the other data is extracted. Thus multi-usage of information resources and the analysis and management of land use information is realized. The information processing flowchart of landuse analysis and management system supported the system can be seen in Fig.2

Figure 2. The information Processing Flowchart of LAMS


Moreover, supported by MIGIS, some experiment work has been carried out by establishing a land resource information system in Liao-ning Province which is under construction. The following two aspects are included.
  1. As an independent graphic station LLRIS, the cata input , edit and display, etc. can be completed . The data which is considered after check, will be directly transmitted into the data base supported by VAX-11/785 and managed by ARC/INFO through the connecting net work of microcomputer and VAX , to realize the program interface between MIGIS and ARC/INFO and file transmission between dBASE and INFO.

  2. Set up LIRIS subsystem --- the geographic names information system. The research will lead spatial graphic display into geographic names information system, and add the interactive editing specific modul for Chinese character geographic name notation.
It is considered that, through the trial production and testing, MIGIS is easy to learn and master, which could raise working efficiency, especially the system simple graphic preprocessing requirement, flexible data inputting and editing mode, the selection of multi topology set up methods and the graphic display output of error information etc. with which user are satisfied. As a kernel software of geographic information system of course, we will further expand, develop new functions, present new version, meanwhile, we will also combine and utilize the research of subject, enrich specific module, develop specific system which is available for different aim, these two main aspects of the system are to be developed in depth.