Discovery And Standardized Processing Of Earth Observation Data In The Web Environment

As Earth Observation (EO) technologies develop continuously, the volumes of data archived in clearinghouses also grow. The complex features and massive amounts of EO data lead to challenges on how to make better use of these data for the community and for public service. On the one hand, different data clearinghouses vary in their data discovery mechanisms and metadata information model to distribute archived EO data, a fact which requires the data user to get familiar with different data clearinghouses and how to interact with them to discover EO data; on the other hand, because the EO data is highly heterogeneous, the user must have a full understanding of the data of interest before further processing In addition, in the Web environment, the data lineage information, which records the evolution of a data processing process, are mostly not recorded. It is difficult to determine the usability and reliability of data when with the data lineage information are absent. Therefore, implementing a one-stop federated catalog service to discover data and providing standardized interfaces to process heterogeneous EO data are important prerequisites for improving the level of application of EO data. Besides, the full expression of metadata, especially the data lineage information, is an important guarantor of the quality level of EO data.This study uses OGC and ISO standards. OGC has developed a series of standards to address EO data sharing and interoperability issues. Catalogue Service-Web Profile (CSW) can be used for publishing, retrieval and management of EO data, services and related resources, and metadata. The architecture of CSW is highly normative and universal, which supports an extended metadata model. The user can use a standardized query language from the clearinghouse based on a standardized CSW interface. By implementation of multiple CSWs, a user could discover data from multiple clearinghouses with a single integrated query interface. OGC Web Coverage Service (WCS) provides a standard, customized interface for raster data, which can execute the format conversion, subsetting, and re-projection operations.After it analyzes several sets of geospatial metadata for EO data, the paper proposes to use the ISO 19115 metadata specification for data discovery and customization attaches more importance to the data lineage model and its implementation framework in Chapter 2. The research on how to enhance the openness for EO data is presented in Chapter 3. Implementation CSW services for several clearinghouses, including NASA, NOAA, and GMU CSISS. As to multiple EO data clearinghouses, the dissertation designs a one-stop federated catalog system, enabling users to discover EO data from multiple clearinghouses through a single standardized interface, using the ISO 19115 metadata specification to describe data from the clearinghouses studied in this dissertation. The heterogeneity issues in data discovery are addressed by using a one-stop federated catalog system. After analyzing the heterogeneity and complexity of different EO data, the dissertation extends the Geospatial Data Abstract Library (GDAL) library to enhance support to the ISO 19115 metadata and data lineage information in Chapter 4. A framework for processing and customizing EO data are established using OGC WCS and the extended model. A prototype system is built in Chapter 5.This dissertation involves the following major research activities:1. Enhancement of the openness of EO data discovery for the EO clearinghouseThis paper studies several EO clearinghouses, among them those of NASA, NOAA, and GMU. The differences among the EO data query interfaces lead to the heterogeneity of data discovery. It presents the use of OGC CSW to enhance its openness for data discovery, and addresses the question of the heterogeneous query interface and metadata model. CSWs for different clearinghouses are designed and implemented to enhance the openness of the EO clearinghouse.2. Establishment of a one-stop federated catalog system for multiple EO clearinghouses.Depending upon how CSW is implemented for the EO clearinghouses studied, the focus is how to design and implement a one-stop federated catalog system for multiple EO clearinghouses. Mediator/Wrapper architecture is used to support a federated catalog system. A query dispatch mechanism is also addressed. The research on how to apply the ISO 19115 metadata standard to describe EO data from different data clearinghouses. Then the implementation of the CEOS WIGSS Integrated Catalog (CWIC) system is used to describe and analyze the key technologies for building a one-stop federated catalog system.3. Standardized customization and processing for EO raster dataGiven the analysis for the complex heterogeneity of EO data, the dissertation proposes to use the GDAL abstract data model as the basis for standardizing EO data and to extend the GDAL model to support ISO 19115 and data lineage information in particular. Study how to build a framework for heterogeneous EO data and implement an OGC WCS to provide the customization functionality for some EO raster data.4. Implementation of data discovery and processing systemWith the implementation of a one-stop federated catalog system and the EO raster customization framework, a prototype system is established. The system can discover EO data from multiple distributed EO clearinghouses, and provide a standardized interface to process EO raster data. This dissertation has the following major innovations:1. Enhance the openness of EO data and build a one-stop federated catalog system for the global EO data resourceSeveral important international EO clearinghouses use different metadata catalog systems and data discovery mechanisms, which lead to heterogeneity in data discovery. Detailed analysis of several EO data sets leads to the enhancement of the openness of data discovery by building a standardized interface. This dissertation focuses on producing an interface to heterogeneous catalog system and metadata model It proposes a one-stop service model for processing EO data from multiple clearinghouses. A one-stop federated catalog system is built to serve global EO data resources, and the system in the international field of EO data that has been widely used.2. Establish the data customization framework for heterogeneous EO raster dataDifferent EO data products generally have different properties, such as the projection and format, which leads to the heterogeneity in data access level. The existing EO clearinghouses provide only access to original archive data, without providing customized data-related services. In order to enhance the interoperability of EO raster data access, the existing GDAL model is extended to support metadata and lineage information. The framework for EO data customization is built and OGC WCS is implemented under this framework.3. Design and implement the prototype system for EO data discovery and standardized processingUsing the one-stop federated catalog system and data customization framework, this dissertation, designs a prototype system to discover EO data resources from multiple EO clearinghouses and to customize heterogeneous EO data.