Ancillary Hydro Point represents locations that have unique hydrology characteristics or monitors or controls stream flow or manages hydrographical spatial data integrity. It is a point feature class of the NSW Digital Topographic Database ( DTDB), within the Hydrography theme. In the database, ancillary hydro point is classified as the following: On End Node, On Centre Line, On Boundary, In Hydro Area and No Topology. On End Node is a hydro management point that has a topological relationship to a hydroline end node. On Centre Line is a hydro management point that has a topological relationship to a hydroline. On Boundary is a hydro management point that has a topological relation to hydro area polygon boundary. No Topology is a hydro management point that has no topological relationship to another feature. An ancillary hydro point can be a bore, lock, rapids, spring, tidal limit marker, water fall, dissipation point, contracted node, hydro data management, regulators, barriers, river gauge, and sink. The attribute values are located in the “class subtype” attribute.
There is no overall accuracy reported in the database, however accuracy of the individual feature instances of each feature class can be found in the database tables. The currency of the feature instances in this dataset can be found in “feature reliability date” or “attribute reliability date” attributes. All feature instances in this class are attributed with a planimetric accuracy value. It is expected that the 90% of well-defined points with the same planimetric accuracy are within 0.5mm of that map scale. Depending on the capture source, capture method, digital update and control point upgrade, every feature instance reported has a positional accuracy within the range of 1m - 100m. For detailed definitions on all feature classes and attributes, refer to the DTDB Data Dictionary.