Structure of drainage asset data
The drainage data hierarchy in GDMS is shown below:
Definitions
Within GDMS, a drainage asset may refer to an individual asset, such as a gully, pipe or ditch, or to a network modelling item such as ghost nodes. These assets are split into one of three types, as defined by CD 535, related to how their map geometry is defined:
- Point assets (e.g. gullies): defined as a point on the map, usually found at the end of one or more continuous assets.
- Continuous assets (e.g. pipes): defined as a single line between two point assets. These point assets are nominated as the upstream and downstream points to define flow direction. Where two or more continuous assets have the same pair of upstream and downstream points, they are automatically grouped into an asset set by GDMS:
- Region assets (e.g. ponds): defined as a polygon on the map, with a corresponding point asset at its centroid.
Drainage asset records include inventory and condition information that pertains to the assets. More detailed information about the asset, including history is provided by linked activities, components and observations.
- Activity: a specific action that occurred on one asset on a specific date, such as a survey of an asset. Where one or more related activities are undertaken, such as a survey contract of multiple assets, these are grouped into an activity set.
- Component: for continuous assets only, inventory information that is applicable to only a part of the asset’s length, such as diameter, material, or lining, may be recorded as a component. Continuous assets have an unbroken, non-overlapping series of one or more components along their full length.
- Observation: detailed information about the condition of an asset or any other information gathered during a survey may be recorded as an observation. The condition recorded against an asset record is derived from these observations.
Multiple connected assets in GDMS are grouped to form an asset system (or drainage system defined in CD 535). Each asset is part of one system at a given point in time. Asset systems are automatically calculated by GDMS and are used to store the current interconnected nature of assets. When drainage asset data is updated within GDMS, system IDs are recalculated, as asset connectivity may have changed.
Unique asset references are assigned to each drainage asset by GDMS at time of first upload and is not changed when asset is updated
Each drainage asset is also snapped to a sub-catchment.