INTEGRATING DATA LAYERS TO SUPPORT THE NATIONAL MAP OF THE UNITED STATES

The integration of geographic data layers in multiple raster and vector formats, from many different organizations and at a variety of resolutions and scales, is a significant problem for The National Map of the United States being developed by the U.S. Geological Survey. Our research has examined data integration from a layer-based approach for five of The National Map data layers: digital orthoimages, elevation, land cover, hydrography, and transportation. An empirical approach has included visual assessment by a set of respondents with statistical analysis to establish the meaning of various types of integration. A separate theoretical approach with established hypotheses tested against actual data sets resulting in an automated procedure for integration of specific layers also has been implemented. The empirical analysis has established resolution bounds on meanings of integration with raster datasets and distance bounds for vector data. The theoretical approach has used a combination of theories on cartographic transformation and generalization, such as Topfer’s Radical Law, and independent research concerning optimum viewing scales for digital images to establish a set of guiding principles for integrating data of different resolutions.