As information technology develops and social infrastructrures are diversified, various users w ant to share more data,especially spatial data. Of course in GIS application, Data sharing issues in GIS community are more and more important, and also Standard gets essential. According to this trend, Korea Government setup the National GIS(NGIS) plan early last year, and organized 5 subdivis ions to implement NGIS. Standardization subdivision undertook the GIS related Standardization tasks. GIS users want to access and share GIS data among various GIS S/Ws and data formats. So GIS dat a transfer standard format will be needed. Purpose of this paper is to examine and survey the current data exchange situations related to GIS standardization in both domestic and international areas, and then to establish standarization draft appropriate to the situations in Korea. This study was mainly done by Korea Telecom, a government run telecomunication company, who is the leading GIS firm with many years' experiences in fields of FM/GIS in Korea. The Scope / Major objectives and method are summarized as follows;
1) Scope and Major Objectives
Tasks to implement at this survey are;
- Examine the present situation and data structure analysis of major GIS S/W
- Survey overseas case
- Establish Standardization Draft by items
- Physical File Structure Analysis of Exchange Standard
- Establish Korean Transfer Standard Draft
The scope of this study is to grasp the current situations of domestic major GIS S/Ws, to analyze these S/W data structures, and to define the GIS data transfer standard through existing transfer standard analysis.
In data structure analysis, three major S/Ws are selected; one is ArcInfo because of its high est market share in World Market, another is INFORMAP which is used by Korea Telecom, and the 3rd is Gothic from Laser-Scan Inc. in U.K.. Detailed Data Structure Analysis was excluded, and this part will be implemented next year(as Data format Conversion Tool Development Step)
Existing major exchange standards are SDTS(as US Standard), DIGEST(as NATO standard), NTF(as U.K. standard). And aims of this project are to analyze the existing transfer standards, and to prop ose the Transfer standard draft appropriate to korean situations. Thus two possibility were consider ed to establish Korean Transfer Standard; one is to adopt the standard as the most reasonable and ap propriate, from existing various exchange standards, the other is to establish the newly,independent exchange standard alone. For the reason of current need to the standard, and acquisition of related technologies, knowhow in limited time, the first one was selected.
But this project peformed with the limitation that the scope of this year only covers overall frame establishment in order to proposes Korean Transfer Standard(Draft), and Detailed Contents or Conversion tool development related technologies(data structure analysis, conversion program algorit hm design, conversion program coding, and so on) will be implemented at future task.
2) Method
In the project implementation, we have established 8 steps toward the Korean GIS Transfer Standard(draft)
<Fig 1 >8 steps on the Project Implementation
2. Details about Implementation
1) Survey of existing GIS S/Ws and Data Formats
To review existing GIS S/Ws current situations in Korea, and to define appropriate transfer s
tandard draft, we examined 96 GIS user sites during April 24 to May 7, 1995. After Survey, We found
that following S/W are being used in Korea ; ArcInfo, INFORMAP, Gothic, Intergraph, GeoVision, Gena
sys II, Geo/GPG.
2) Survey of existing data standards
To define Korean Transfer Standard, we first review the existing data standards. In surveying Transfer Standards, we have concentrated on three transfer standards(SDTS, DIGEST, NTF) after revie wing various national and international transfer standards. In surveying 3 transfer standards, we co ncentrated on two aspects; one is internal content(spatial data model, data structure, transfer and encoding method, and so on), and the other is external environment(usage, adoption process, and envi ronment, maintenance mechanism, related organization, related effect, and so on)
Because there was little difference among SDTS, DIGEST, NTF in internal aspect, we have been
interested in external aspects. Though evaluation we realized that are 2 categories in transfer stan
dard; one is national standard which all themes integrated within same domain(nation), the other app
lication-specific standard(e.g. DIGEST, DX-90).
3) Why SDTS ?
* General Aspects
- Generality and General Purpose
- Open System (possible to exchange with any spatial data)
- Integration and Harmonization
- Interoperability, Extensibility, Flexibility
* Specific Aspects in Korea
- Current Domestic Requirement(Various GIS users in various applications and Transfer Standard)
- Harmonization and Agreement among the various domestic interests for data exchange
- Proven Stability by using already tested Standard
- To maintain coordination with the international general standard
4) SDTS based Korean GIS Transfer Standard
Based on original SDTS(FIPS 173), KSDTS(Korean Spatial Data Transfer Standard) is established with proper change to Korean situations. That is, theoretical, Conceptual Models and Transfer Method are accepted from original SDTS without any changes.
Spatial Data Definition is without change. So in KSDTS, Conceptual Model of Spatial Data is co mposed of 3 parts; model of spatial phenomena, model of spatial object, model of spatial feature.And in Data quality Part, major 5 parts are included; lineage, positional accuracy, attribute accuracy, logical consistency, completeness. Regarding metadata, there is no metadata standard in Korea. So "Content Standard for Spatial Metadata" by FGDC applies to SDTS, and also is included to KSDTS.
In spatial Data Transfer Specification part, logical structure and physical structure are almost
same. Coordinate representation, attribute representation, declaration method are specified as almo
st same as SDTS, except that English de claration method is same, but for Korean character declarati
on is conformed to KSC 5601.
5) User Need Assessment
- User need assessment was evaluated through followings
- How to need Standardization
- How should be Characteristics of Transfer Standard ?
- Expectation of Transfer Standard
- Review by Area, Size, Business
Please refer figure 2 for the process of user need assessment.
<Fig. 2>
During the process for establishment of detailed Implementation plan and Proposed GIS Transfer Standard(draft), we have to create data dictionary by comparing SDTS Part 2(Entity list) and Digital Mapping Guideline of NGI(National Geographic Institute).
Please refer figure 3. Entity list in Digital Mapping Guideline of NGI(National Geographic Ins titute), and matched both SDTS entity and mapping code of NGI. After that, Modified Entity list repl aced the original SDTS Part 2. At present Entity List Standardization are being implemented by Digit al Cartography Division under NGIS. When the standard for Korean Entity is decided, it will also be included.
<Fig. 3>
6) Establishment of Standardization method
Standardization methods are established by considering steps below;
* Conceptual Model
As SDTS's conceptual model is as a general, flexible data model, KSDTS also adopted this secti
on. Conceptual model allowed users to transfer all types of GIS data formats. Its model has 3 parts
of submodels; model of spatial phenomena, model of spatial features, model of spatial objects.
* Coordinate System
From 1970's to now, Korea has used TM(Transverse Mercator) coordinate system. In TM coordinate system, Korea has been divided to three subzones with 3 axis (125, 127, 129 easting longitude)(easte rn area, central area, western area), and original point at each subzone is intersecting point that crosses with central longitude and 38 north latitude. The projection that was applied to that coor dinate system is Transverse Mercator projection, and Applied scale factor is 1.000.
Because SDTS <Part I> has not defined TM coordinate system as major coordinate system,
KSDTS added TM to coordinate system section (4.1). Also in <Part 4> as TVP(Topological Vector
Profile>, TM also was added.
* Data Quality
There was no experiences for digital GIS data in Korea, data quality issue as well as transfer
standard is not well defined up to now. We do not have any special experiences in data quality fiel
ds, so KSDTS will use SDTS data quality specifications, which is divided into 5 parts; lineage, posi
tional accuracy, attribute accuracy, logical consistency, completeness.
* Metadata
Like the data quality, metadata also is not familiar to Korea GIS user. When metadata concept
was introduced from last year, most users got to know its importance increasingly. As SDTS contains
metadata in the form of several modules, KSDTS also took same type.
* Datailed logical transfer standard
Logical transfer model is object-based, supports vector and raster data model. And this model
adopt modular structure, SDTS defines all 34 modules, each module has its characteristics, contents,
and a module is composed of more than one record, record is composed of more than one fields. A mod
ule at logical level is converted to a file at physical level through transfer process.
3. Conclusion
During this study, we have expects effects;
- Contribution to NGIS Standardization Activities
- Application to detailed Standard Establishment Implementation
- Acquisition of GIS Interoperability
- Cost Reduction in establishing Data Infrastructure
* Future Plan
This study was mainly focused on GIS Data Transfer Standard Definition appropriate to Korean
situations, based on the SDTS as US Federal Standard. Because we had a short time to review SDTS and
existing main transfer standards, and soon, it is difficult to capture the detailed body, and define
Korean GIS data transfer standard completely. But NGIS decided to adopt the Korean Spatial Data
Transfer Standard based on SDTS, and this study contributed to decide the KSDTS. Future plan is to
complete KSDTS, and to develop conversion tool with major GIS S/W.
References
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