The Bureau of Transportation Statistics (BTS) is distributing a set of geospatial datasets in the National Transportation Atlas (NTA). A common file structure was created for each geospatial feature type dataset: points, lines, and polygons. The file formats were designed to make it easier for the user to view and extract the data. The datasets will be distributed in this format until the Transportation network Profile is adopted as part of the Spatial Data Transfer Standard (SDTS). The datasets represent the transportation layer of the National Spatial Data Infrastructure (NSDI). The NTA is comprised of: network datasets, including roads and railroads; point facilities, such as Amtrak stations and airports; and reference datasets such as state boundaries and urbanized areas. The intent of this paper is to introduce the NTA to the ArcInfo community.
The Library of Congress and several geographic information companies, including Environmental Systems Research Institute, Inc., and Hewlett-Packard have established The Center for Geographic Information to promote and enhance the collections and services of the Geography and Map Division. The Center will coordinate the contribution of resources and knowledge from a wide spectrum of the GIS industry to: Aid the Geography and Map Division in its transition to the age of electronic maps and digital forms of geographic information through advice and financial support. Facilitate sharing the Geographic and Map Division's resources electronically. Promote the use of GIS by libraries, academia, industry and commerce, education, and the general public. Encourage donations of digital spatial data sets by American and foreign governments, industry, and academia. Advance the Library's publication, education, and exhibition programs in geographic information and cartography. The purpose of the paper is to provide an update of the paper on the Library of Congress that was presented in Prague this fall.
Over the past twenty five years, enormous volumes of digital spatial data have been collected through various techniques such as automated mapping, geographic information systems, and image processing applications. Data access to these large databases may be constrained by the need for a geographic information system (GIS) or a desktop mapping system, constraints that often preclude broader use of spatial information. While these data are easily shared among a smaller workgroup, the distribution of data cross an organization's network or the internet, has been more problematic. This has resulted in multiple copies of these data and various compression routines applied to the larger image formats stored within these databases. Without highly structured procedures or specific cataloging (metadata) to manage this replication, the decisions and integrity of these data are highly suspect. A suitable client/server model that emphasizes asynchronous cooperative processing between the client and the server tasks is discussed as one of the means of distributing these large spatial databases across the internet.