Generalization for The National Map with emphasis on

The National Map (TNM), being developed by the United States Geological Survey (USGS), is created from many data sources and Web Map Services (WMS) owned by many organizations. TNM data sources are electronically stored at various scales and resolutions. Consequently, when data are extracted from several WMS and horizontally integrated in geospatial data applications, the differences between data sources become apparent. The ability to render one or more scales of TNM data into an appropriate, or functionally equivalent, representation at a user-specified scale could substantially enhance analysis capabilities of these data. This paper describes ongoing research by the USGS into automated generalization approaches that address this problem, focusing on the National Hydrography Dataset (NHD) layer of TNM. The NHD provides vector representations of surface water features depicted at medium, high, and local resolutions, with only medium resolution currently available nationwide.