Geospatial metadata server: on-line metadata database, data conversion and GIS processing

Abstract

The growth of the Internet and more specifically, the World Wide Web allows users, providers and site administrators of geospatial data to share information amongst each other. This helps minimise the time and costs associated with data collection and base mapping. The aim of this research is to better understand fundamental issues and software concepts that influence how geographical data is stored, catalogued and processed over the Internet. This is accomplished by, in part, developing an integrated system that merges existing technologies such as an HTTP server, a RJDBMS and a GIS to facilitate the on-line search of standardised metadata along with the access and conversion of geospatial data. The prototype system developed to meet this aim is called the Geospatial Metadata Server (GMS).

The software prototype evaluates the problems and issues by suggesting strategies that might influence and improve the further implementation of on-line systems designed to share geographic information. The database uses standardised metadata, which enables on-line data dissemination sites to integrate indexing and querying capabilities amongst themselves and ensures that data providers and users share the same terminology for describing geospatial data. The use of an RDBMS substantially increases the speed and flexibility of query operations alongside the storage and report facilities for metadata. Because of the size of metadata records, the system provides the useful feature of parsing entire metadata files and loading the information directly into the database. Metadata files can also be manually entered, updated or deleted on-line in a way that divides the arduous task of entering text via forms into several separate parts. The amount of information contained within a metadata file that is necessary to represent appropriately one or more geospatial data sets is well beyond what the producer of the geospatial data is willing to enter into an on-line metadata catalogue in a single sitting.

Geospatial data occurs in a variety of different data formats. This is a fundamental cause why GIS software packages (supplied by different GIS vendors) fail to operate between themselves. An easily accessible on-line data conversion utility for GMS was developed that is capable of inter-converting between pre-defined geospatial data formats. By examining the information retrieved from the database and feeding it to the server's software, the search engine integrates the metadata database and the conversion utilities. The resulting implications are that on-line GIS software is tailored to respond automatically to a Web search engine and that metadata, geospatial data and GIS software is able to exist separately on different physically remote servers. The implication is that Internet technology is becoming the basis for a new computing architecture for GIS by addressing the technical and institutional issues that arise in accessing and using on-line geographic information.