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NHDPlus Smoothed Layers
NHDPlus catchments form the basis of the NHDPlus data model. Based on USGS 1:100,000 quad maps, NHDPlus catchments are highly complex polygons posing a challenge for analysis or display (see NHDPlus documentation ). Smoothed NHDPlus catchments and NHDPlus regions are a generalized version of the original NHDPlus catchment data, with roughly 85% fewer vertices. These layers are useful for display purposes or for determining the NHDPlus region of a feature. Note that the generalization process may result in inaccurate analysis results along the smoothed feature borders. Users should weigh the performance gain verses accuracy loss when utilizing smoothed NHDPlus layers.
Layers currently stored in the WATERS instance:
Generalized NHDPlus catchments.
Aggregation of generalized NHDPlus catchments into composite NHDPlus regions.
Storage Details for NHDPlus Smoothed Layers
- Metadata for all smoothed layers is available via the GeoData Gateway by clicking on the metadata buttons above.
- Smoothed layers are stored in the same coordinate space (NAD83) as RAD and NHD layers.
- Smoothed layers are registered to ArcSDE allowing use by any ESRI client.