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The HydroAdd Practice Data are a group of editable web layers shared publicly on ArcGIS Online (AGOL). The web layers are intended as practice data for new users of the USGS HydroAdd tool. The USGS will create, share, and maintain the HydroAdd Practice Data periodically.
HydroAdd is a web tool built by the USGS National Geospatial Technical Operations Center (NGTOC). HydroAdd is a GIS tool for addressing, or referencing, diverse external datasets to the National Hydrography Dataset (NHD). For example, a user can use HydroAdd to address locations of stream gages or field observations of fish presence. Any type of water information can be addressed to the NHD, making HydroAdd useful for a broad range of applications.
HydroAdd allows users to edit the geometry of the features in their web layer to be coincident with NHD features. HydroAdd also spatially joins some of the NHD attributes to the users’ web layer. Users cannot edit the NHD with HydroAdd, as it is displayed as a read-only reference layer in the HydroAdd application.
To address data to the NHD with HydroAdd, users normally make their own data available to HydroAdd as an editable web layer from AGOL. For new users or those without editable practice data, HydroAdd also includes a default practice web layer. The practice web layers are mock observations and do not represent any real USGS data products. The HydroAdd Practice Data allows new users of HydroAdd to practice addressing with HydroAdd before they assume the effort to create their own web layers with AGOL.