IMPROVING GIS DATA SHARING IN CHINA

Huang Yuxia1 He Jianbang1 Ke Zhenyi2 Chen Changsong1

1. Institute of Geography, Chinese Academy of Sciences , Beijing , China

huangyx@lreis.ac.cn

Jbhe@dial.cashq.ac.cn

Ccs@bj.col.com.cn

2. Zhejiang Agriculture University, Hangzhou, China

zhyke@peony.zjau.edu.cn

[ABSTRACT]

With the development of advanced technology and science, a large number of distributed data in heterogeneous systems needs to be shared. This is also very important to present situation of geodatabases in China. There are a lot of isolated geospatial databases used in the departments and communities. Moreover, most databases have their own data format and data structure, but it is necessary to put them to network and to share them in a distributed computing environment. Therefore, all databases that should be shared must be improved. In order to reach this goal, the government policy and strategy is the first step to assure the success. Standardization is a key step to achieve this purpose. Furthermore, Open GIS interoperability technology is an important step to support realization of this geodata strategy. The idea of this paper is to show how to realize GIS data sharing from these three main aspects in China.

1. INTRODUCTION

In 1994, after the conference of "Environment and Development" (Brazil), the white paper, "The 21 Century Agenda of China", which is the first national strategy paper on sustainable development was established. From that time, China has paid high attention to the field of sustainable development. In order to realize this grand project, the process of reforming national information must be promoted, especially for the information infrastructure in GIS. With the development of information technology and Internet, it is very necessary to realize data sharing in distributed, heterogeneous systems, because there is only one World , and therefore, we must share data. In order to achieve this goal and realize data sharing, since the 80's , under the leader of government, technology revolution for some basic databases and especial databases of survey, resource, environment and regional economy has been promoted and related policy has been improved as well. This paper presents some preliminary proposals for government policy, standardization and technology support, which are very important in the process of realizing GIS data sharing in China.

2. THE GOVERNMENT POLICY AND MANAGEMENT OF GEODATA SHARING

Geodata sharing is the motivation force in the process of developing GIS products. In order to realize this object, government policy for GIS data management is the first step. In China much research work is ongoing. There are two major tasks in this research field:

* Firstly, to persuade, motivate and absorb all unites who hold GIS data to take part in the process of GIS data sharing to realize GIS data sharing in the whole country.

* Secondly, to coordinate the relationship among units and users which are the data providers or users.

In order to solve these problems, there are many aspects to be considered. For examples: public, secrete and protection of GIS information; free or pay for data sharing; the price of information and service, and so on.

* Moreover, according to copyright and patent law, the rules how to protect the information holders must be built.

* Furthermore, the price of the information and service will be set up with the relation to the cost of production, the cost of effectiveness, social benefits and the trend of supply and demand. Therefore, three degrees are divided: ordinary prices, preferential prices and exceed prices. Ordinary prices is the price of information, which means the total sum of its production cost, service cost, profit and so on. Preferential prices is only the production cost, and exceed prices is the price which beyond its ordinary prices.

 

3. STANDARDIZATION OF GEOINFORMATION (GI)

Standardization of GIS information is the key step to realize GIS data sharing. This is the very broad field of research. In China, after long and deep research, a lot of achievements has been worked out in this scientific research. This paper only presents the formal framework of standardization, classification and encoding of GIS information.

3.1 The framework of GI standardization

Figure 1 is the formal description of Geoinformation (but only shows the main parts, not the whole, [ ... ] stands for this index which can be chosen.)

This formal description describes the property of all geospatial data, independently of any data structure and data format in GIS. The characteristics are in the following:

Firstly, geospatial feature entity and geospatial feature non_spatial attribution index are set separately.

Secondly, time index, quality index and data sharing index are separately set for geospatial feature entity and non_spatial attribution. Time index is used to guarantee the validity of geospatial feature entity and non_spatial attribution, and history document is established by these information. Quality index is used to interprete the information such as intersect, duplicate, multi_scale and multi_semantic in multi_resource databases in GIS to ensure the correctness in the process of translation. In addition, the quality index of geospatial entity emphasizes the precision of its position and the quality of non_spatial attribution emphasizes the precision of its attribution. The sharing index is used to express the share of geospatial entity and its attribution.

Thirdly, the identification index of spatial feature entity and its spatial position are indispensable. And the identification index of non_spatial attribution is also indispensable.

The last, the metadata index is used to describe the whole property of GIS data file and the set of files.

Figure 1

 

3.2 The classification and encoding of geoinformation

Line classification and segment encoding are adapted to classify and encode the geospatial entity and non_spatial attribution.

a) The classification and encoding of geospatial entity

Classification

According to the relation and interaction among these entities, all geospatial entities will be classified under the common standard, as shown in figure 2. The first level consists of the basic geospatial entity and the expert geospatial entity. The basic geospatial entity is the basic and common public platform for the expert geospatial entity. The second level in the basic geospatial entity includes control points, administration area , road, bridge and water body etc. which are the essential geospatial entities. The second level in the experts geospatial entity includes land district, water district, ecology environment district, economy district etc. which are classified for special use. According to this rule, the third and forth level of the geospatial entity will be given.

Encoding

Geospatial entity is divided into two parts: main coding and appendix coding. Main encoding divides into three segments: the first segment corresponds to the first level of classification in the geospatial entity, and the second segment corresponds to the second level of classification in the geospatial entity. And the third part is the classified encode coming from the corresponding expert databases with the same length.

The length of appendix coding is three. The first is the time index which expresses time attribution of the geospatial entity; the second is the quality index which expresses quality attribution of the geospatial entity; and the third is the share index which shows sharing attribution of the geospatial entity. In all of these three characteristics "1" stands for switch on, "0" stands for switch off.

Figure 2

 

 

b) The classification and encoding of non_spatial attribution

Classification

Line classification is adapted in the classification of non_spatial attribution. For example:

In the first level classification of the expert of geospatial entity "land district", there are some non_spatial attributions, such as "land use", "land plan" and "land change", and so on. And in " land use", there are some attributions such as " the total area of land ", " the area of land use" etc. Furthermore, there are still some attributions such as "the area of paddy field" and " the area of dry land" belong to " the area of land use".

Encoding

Non_geospatial attribution coding is divided into three parts: head coding, body coding and tail coding. Head coding is the main part of the coding of non_spatial attribution and expresses this attribution belongs to which kind of geospatial entity.

Body coding consists of three segments. The first segment indicates the order of this attribution in all attributions, which expressed by one Latin Alphabet. The second segment which expressed by one Arabic Alphabet, indicates his property, including identify index, property index and quality index, etc.

For example, " 1 "stands for identify index, "2" stands for property index, and "3"stands for quality index. The third segment comes from the coordinated attribution coding which existed in the databases.

Tail encoding consists of two binary alphabets, whose function is the same as the appendix coding of geospatial entity.

 

4. THE TECHNOLOGY SUPPORT OF GEODATA SHARING IN GIS

We only consider the technology environment and architecture under the network environment to realize the sharing in distributed heterogeneous geodata and geoprocessing resources. At present, the technology in China of realizing the data sharing is to combine it with integrated management and distributed management.

But in the future, the completed distributed management will be adapted. The technology architecture of system is shown in figure 3.

The architecture of this system consists of:

1) The main network center of data sharing:

The function of this center is not only to integrate all information from every distributed group, but also to manage and co-ordinate all distributed groups, as well as to be responsible for all technologies so that all network will work under the good condition.

2) Distributed network centers at the main communities

The function of these distributed centers is to submit the information which will be shared in the whole network to the main network center, and supply the shared information to own users in its community as well.

In order to realize data sharing, main network center and every distributed network center have their own web browses, servers, data-sharing databases and metadata-sharing data bases.

 

 

 

 

Figure 3

 

5. CONCLUSION

Sharing of geodata, especially Geoinformation is an urgent need in future development of informatization in China. In order to realize geodata sharing in GIS, the government policy, standardization and technology support are very important. The decision process for geodata sharing must take into account the motivation and integration of all geodata centers to take part in sharing of existing geodata, and coordination of relationship among these centers and users, as well as the technology support for common standardization to realize the data sharing in GIS. Furthermore, in order to provide GIS data from China for global use, the adoption of international geographic information standards is important. Nowadays, China is the one of positive members of ISO/TC211. Therefore, we believe that in future GIS data sharing in China will be developing fast and be based on global principles of geodata and geoprocessing interoperability.

 

REFERENCE

He Jianbang, Ke Zhenyi, Mao Feng, Chen Changsong, Huang Yuxia, Zhang Xiaodong, project report " Data sharing for sustainable development in China", Beijing, 1998