Abstract
Generalization of the National Hydrography Dataset
Track: Water Resources
Author(s): Jeffrey Simley
The NHD represents the surface water of the United States at a nominal scale of 1:24,000. The data needs to be generalized to create representations at smaller scales and the need for normalizing the data to a uniform density since the 1:24,000-scale dataset is in-fact composed of a multitude of scales producing different densities. There are two basic approaches to generalization: the pruning, or elimination, of features, and the simplification of the features. Polygon pruning is a straight-forward process. Vector network pruning can be accomplished based on thresholds of upstream drainage areas. Feature simplification through adjustments to the vertexes that define the feature can be accomplished using traditional and recently developed methods. The results of this work show that the objectives can be achieved. The challenge is to move the technology from a developmental setting to a massive nationwide application involving a 7.5-million mile linear network and 6.5-million polygons.
Jeffrey Simley
U.S. Geological Survey
P.O. Box 25046, MS-510, DFC
Denver , Colorado 80225
United States
Phone: 303-202-4131
Fax: 303-202-4020
E-mail: jdsimley@usgs.gov