Telcordia Geospatial Information Filtering System (GeoLens)

This page provides technical information about GeoLens architecture, development and technological inputs.

Background

In March 1994, NASA's Information Infrastructure Technology and Applications (IITA) initiative of the High Performance Computing and Communications (HPCC) program issued a Cooperative Agreement Notice (CAN-OA-94-1) , "Public Use of Earth and Space Science Data Over the Internet". In response, the Universal Spatial Data Access Consortium was formed (then consisting of Bellcore, Camber Corp., the OpenGIS Consortium, Rutgers Center for Remote Sensing and Spatial Analysis, NASA's Space Science Data Center, and the California Resource Agency's CERES Program). The USDAC submitted a proposal for a project entitled, "Usability and Interoperablity: A Dual Strategy for Enabling Broader Public Use of NASA's Remote Sensing Data on the Internet." This project was funded for three years under the Digital Library Technology Development Area of Interest in the CAN and the USDAC received $2.3M from NASA and contributed another $2M in cost-sharing.

The "Problem"

Geospatial data are difficult to use because they:

• are not easily found on the Internet,
  
  
• are stored in different data formats, models, and structures,
  
  
• exist in extremely heterogeneous computing environments, and
  
  
• often require much technical knowledge about remote sensing, cartography, geodesy, and computing to search, extract and use them with other data.
  
  

Overall Approach

Propose a comprehensive strategy that makes geospatial data more usable and interoperable by:

• Implementing OO design and new data models to: (1) encapsulate remote sensing and other geospatial data in objects, and (2) build Web/Internet-compatible object access services to facilitate interoperability.
  
  
• Developing an innovative, easy to use metadata browser.
  
  
• Making use of existing public domain software and information processing standards whenever possible.
  
  

GeoLens Architecture

The figure below illustrates conceptually the distributed Web/Internet architecture of the GeoLens System. The system consists of a GeoLens Client, a GeoLens Catalog Server, GeoLens Data Access Servers and, potentially, other servers to process geospatial data or their metadata.

(Enlarged diagram is 35KB)

The GeoLens Client locates geospatial data on the Internet by using an agent called the "GeoLens Catalog Server" to search metadata catalogs. A Metadata Analyzer and Schema Loader extracts metadata for geospatial data objects as they are added to a repository. These metadata are analyzed for their type, range and other properties, and their schema is determined. Metadata are then added to a catalog, in this implementation an O2 database, and schema information is authenticated by a Schema Mapping Server before updating its repository of cross-schema attribute mappings. A user launches a search for geospatial data by querying the contents of metadata catalogs with the help of one or more GeoLens Catalog Servers. Catalogs may be queried for the schema used to structure and document metadata for a collection of data objects, or for any of the attributed metadata that describe a particular data object. Queries may be spatial, temporal or built from any metadata attributes used to catalog a data object. Since a query may be issued to one or more catalogs, each with collection metadata that might be organized consistent with different metadata schema, a Schema Mapping Server may be invoked by query services provided in the GeoLens Catalog Server to translate between schema with different attribute names and structure. This feature enables a user to search recursively all or part of the catalogs known to GeoLens Catalog Servers for geospatial data objects that satisfy a query.

Once a list of candidate data objects has been returned to the GeoLens Client, a user can select objects from this list for retrieval. The GeoLens Client sends a message to a GeoLens Data Access Server with the ID for the data object and a user-provided Minimal Bounding Rectangle. This MBR is applied by the GeoLens Data Access Server to clip the data object. The data extract is remodeled as an OpenGIS-like Well-known Structure (WKS) and returned to the GeoLens Client where it may be stored locally, or immediately exploited by an application, e.g., a commercial GIS, that implements OpenGIS interfaces. In addition, the GeoLens architecture provides support for other services, e.g., geoprocessing, that may be requested by the GeoLens Client or GeoLens Data Access Servers.

A major thrust of the GeoLens Project involves the evaluation of new Web/Internet technologies, support of Federally-mandated information processing standards, and use of public domain software to implement GeoLens clients and servers. With these objectives, highlights of the current GeoLens system include:

• Support for dynamic schema (including FGDC and ECS metadata standards), translations between schemas, and recursive queries of GeoLens catalogs
  
  
• A full-feature scalable catalog server built on a commercial OODBMS
  
  
• Data access servers that implement coverage types and interfaces consistent with those described in the OpenGIS Abstract Specification and return extracts of data objects
  
  
• A Java-enabled client featuring a sophisticated graphical interface for viewing metadata trees and their attributes and for forming map/image-based spatial queries
  
  
• A client-server model implemented on WWW-Internet infrastructure
  
  
• A flexible approach to catalog federation that exploits a general-purpose encapsulation mechanism to encapsulate access-descriptive metadata
  
  

Online Demo

- The GeoLens demo with scripted highlights!

Technical Documents

These documents describe GeoLens software requirements, architecture and features.

• GeoLens Requirements (1994)
  • html
  • postscript
• GeoLens Use Case Scenario
  • html

Also see:

Pointers to related Digital Library technologies that have informed design of GeoLens.

• OGC's OpenGIS Abstract Specification

• GeoLens and related work

  • L. Shklar, K. Shah, and C. Basu. Putting Legacy Data on the Web: A Repository Definition Language, Special Issue of "ISDN and Computer Networks", Proceedings of the Third International WWW Conference'95, Vol. 27, #6, April 1995.
    
    
  • L. Shklar, A. Sheth, V. Kashyap, and K. Shah. InfoHarness: Use of Automatically Generated Metadata for Search and Retrieval of Heterogeneous Information, Proceedings of CAiSE'95, June 12-16, Jyvaskyla, Finland, Springer-Verlag Lecture Notes in Computer Science #932.
    
    
  • L. Shklar, K. Shah, C. Basu, and V. Kashyap. Modelling Heterogeneous Information, Proceedings of the Second International Workshop on Next Generation Information Technologies (NGITS'95), June 27-30, 1995, Naharia, Israel.
    
    
  • L. Shklar, C. Behrens, C. Basu, and E. Au. New Approaches to Cataloguing, Querying and Browsing Geospatial Metadata. Paper presented at the 2nd IEEE Metadata Conference, Silver Springs, MD, Sept. 16-17, 1997.
    
    
  • Behrens, C., L. Shklar, C. Basu, N. Yeager and E. Au. The Geospatial Interoperability Problem: Lessons Learned from Building the GeoLens Prototype, Paper presented at the Interop '97 Conference. Hosted by NCGIA/NSF/OGC, University of California, Santa Barbara, December 3-4, 1997.
  
  
  

• Telcordia Document Browsing and Indexing Technology

  • Telcordia Latent Semantic Indexing Software
    
    
  
  

• Other Map and Image Browsers

  • USGS WebGLIS
  EOSDIS V0 IMS WWW Interface
  • CORE Software's ImageNet
  • BigBook
  • US Census Bureau's Tiger Mapping Service
  • ADL on the Web
  • FGDC Clearinghouse Browser
  • DAAC-in-the-Box Server
  • Xerox PARC Map Viewer
  • MapQuest
  • MassGIS Orthophoto Browser