Research and Implementation of the Management of Geospatial Metadata

It is very important for most GIS users to get the geospatial information from various districts. The information distribution technique based on Internet can play a great role in the service. In order to allow GIS users to know something about the production of geospatial data in time, geospatial information distributed system must be set up in NGDC. Through Internet, GIS users will be able to query what geospatial data is being produced, how about its quality, where it is produced, and so on. To maintain geospatial metadata is a key task in setting up the geospatial information distributed system through Internet.It is only after searching and querying corresponding geospatial metadata that users can clearly know what geospatial data is available for them, what geospatial data they are interested in, where the information is stored. Firstly, this paper presents the concept of geospatial metadata. Then it analyzes the difficulties and challenges in the management of geospatial metadata,including:①lack of the specifications and standards of geospatial metadata; ②too many geospatial metadata items;③ complicated inner relationship among metadata items. With the example of the metadata manager in GeoStar which is a domestic GIS fundamental software,the functions of the geospatial metadata mangement system are made clear.It is through ODBC that Geometa,the geospatial metadata management system access and manipulate the geospatial metadata tables. Finally,a model of geospatial metadata management in national geospatial data clearinghouse is proposed.It can be described as follows:Geospatial data producers submit the corresponding geospatial metadata information together with their geospatial products to NGDC.In other words,the providers are responsible for creating metadata of their geospatial products in digital form,updating them promptly and submitting the metadata to NGDC in time.NGDC is in charge of geospatial meta-database maintenance and geospatial metadata service,especially metadata query service.Through Internet,users can search the geospatial metadata maintained in NGDC to find out the geospatial data sets that are suitable for their applications.Then the users can download the specimen data to their own computers or submit directly orders for any desired geospatial product to relative providers or NGDC if the geospatail products are available for them.