TVD Connectors
A TVD connector provides a link between data streams in a Time Series Database (TSDB) and objects in the network.
TVD connectors have point geometry and optionally polygon geometry (for spatial data such as rainfall, evaporation and temperature), and can be digitised on the GeoPlan as either a point or polygon object. See Digitising Network Objects for details.
TVD connectors may be digitised as point or polygon objects but they will only appear in the Polygons grid.
A TVD connector reads data from the TSDB or from another TVD connector or uses a specified constant. This data may then be used as an input to a connected network object or to compare observed results and modelled results for a network object. See TVD Connector Data Fields (InfoWorks) or TVD Connector Data Fields (SWMM) for information about defining a TVD connector.
The use of TVD connectors to configure the use of time varying data stream stored in Time Series Database objects is used as an alternative approach to the use of Event objects to store time-varying data. Time Series Database objects cannot be used in simulations in conjunction with Events with the exception of Waste Water and Trade Waste events.
When used as an input to a connected object in an InfoWorks network, TVD connectors may be used to control Regulator objects by directly controlling the regulated variable of the object. The TVD connector may also be used as an input to an RTC table to indirectly control the regulator via Real Time Control. See Controlling Regulators using TVD Connectors for details.
When used as an input to a connected object in a SWMM network, TVD connectors may also be used to control Regulator objects. See Controlling Regulators using TVD Connectors (SWMM) for further information.
If the TVD connector is to use TDSB data, up to three data streams can be read into the TVD connector; Input A, Input B and Input C. The data streams are listed in priority order, the lower priority data streams being used to fill in gaps in the data of the higher priority streams. I.e. if data is missing at a particular timestep in Input A, InfoWorks ICM looks for replacement data in Input B; if data is missing at the same timestep in Input B, values from Input C will be used if available.
A constant value can also be specified for a TVD connector, when you want to apply, for example, a constant evaporation that is typical for the network location that is being modelled. You can specify up to three constants for the TVD connector using the Input A, Input B and Input C fields.
SQL expressions can also be added to a TVD connector. You can use an expression to calculate tidal harmonics or to enable data in a TSDB to be transformed into a value which is appropriate for your model. For example, you may use an expression to apply a rating curve or to fill in missing data in the data stream (overriding the priority order of the three input data streams mentioned previously).
Any SQL expressions will be automatically evaluated during an appropriate Run. See the TVD Connector Data Fields (InfoWorks) and TVD Connector Data Fields (SWMM) topics for further information.
TVD connectors in InfoWorks networks
TVD connectors as rain gauge polygons
TVD connectors with polygon geometry can be used in conjunction with rain gauge boundaries. These rain gauge polygons may be used in conjunction with spatial rainfall data provided from Spatial Times Series Databases.
The order of priority of applying spatial rainfall data to the network can be defined using Spatial Rain Sources. If spatial rain sources are not specified, order of priority is determined by the order of the TSDB data in the Schedule Hydraulic Run View.
Area-averaged rainfall
By default, for a particular subcatchment, InfoWorks ICM assigns rainfall from the TVD connector that contains the centroid of the subcatchment.
For very large subcatchments, where the subcatchment overlaps multiple raingauge polygons (or radar cell boundaries), using only the raingauge polygon that contains the centroid can mean that the simulated subcatchment rainfall is not representative of the rainfall over the subcatchment as a whole.
Check the subcatchment's Use area-averaged rainfall field to calculate the rainfall for the subcatchments as the area-average of the rainfall from all raingauge polygons that overlap the subcatchment. If the subcatchment falls wholly or partly outside any raingauge polygon, the simulation will fail with an error during pre-processing. If the subcatchment does not have a boundary, the option is ignored.
The following variables are not area-averaged:
- Evaporation from TVD connectors
- Temperature from TVD connectors
- Runoff initial conditions
Instead, the values used are those that would apply if using only the rainfall polygon that covers the greatest area of the subcatchment.
Note that the recommended way to set runoff initial conditions for a subcatchment in InfoWorks networks is via the Subcatchment or Surface tabs in the Catchment Initial Conditions.
Using TVD connectors for ARMA calculations
ARMA, or Auto-Regressive Moving-Average, is a method for error prediction. In InfoWorks ICM, ARMA is used to:
- Calculate the difference between actual observed flows from a subcatchment and the runoff predicted by a model. In this operation, a TVD connector is used to connect either a TSDB data stream or another TVD connector which provides the observed flow to a subcatchment that the TVD connector is also connected to. This allows the observed and predicated values to be calculated using the ARMA model during a simulation.
- Post-processing forecast predictions. In this operation, the TVD connector is used for post-processing the model output. Using the observed data and the relevant ARMA model, the model output can be corrected during a simulation for specific objects that the TVD connector is connected to.
See Using ARMA in InfoWorks ICM for further information about to configure a TVD connector.
Using TVD connectors to query average spatial rainfall
It is possible to create a TVD connector with polygon geometry which will contain the averaged spatial rainfall result for a given simulation, using rainfall data from spatial TSDBs. The TVD connector polygon can be located outside of the existing network. It is possible to display a graph and grid of the result.
See Using TVD Connectors to Query Averaged Spatial Rainfall for further information.
TVD connectors in SWMM networks
Spatially varying rainfall from a scalar TSDB
The type of geometry used to create the TVD Connector determines if time varying rainfall data from a scalar TSDB linked to the connector is to be applied spatially or non-spatially to subcatchments during a simulation:
- Polygon - rainfall data stream profiles, assigned to a TVD connector with polygon geometry, are applied to any subcatchments whose centroid (defined by the subcatchment's X, Y coordinates) lies with the TVD connector polygon boundary. This allows the TSDB rainfall to spatially vary within and across subcatchments. If no X and Y coordinates have been specified for a subcatchment, ICM will use the coordinates of its Drains to node or subcatchment as the centroid, and if the Drains to object has no coordinates, ICM assumes the centroid's coordinates are 0,0.
- Point - rainfall data stream profiles, assigned to a TVD connector with point geometry, are applied to a subcatchment via the rain gage associated with the subcatchment. This means that the TSDB rainfall will be applied to the area defined by the subcatchment's boundary, and no spatial variation will occur within any subcatchment that references that rain gage.
To reference a TVD connector from a rain gage, ensure that the name of the Rainfall profile in the rain gage properties is set to the name of the applicable TVD connector.
Spatially varying rainfall from a spatial TSDB
TVD connectors with polygon geometry can be set up as rain gauge polygons. These TVD connectors/rain gage polygons may be used in conjunction with spatial rainfall data provided from Spatial Times Series Databases.
The order of priority of applying spatial rainfall data to the network can be defined using Spatial Rain Sources. If spatial rain sources are not specified, order of priority is determined by the order of the TSDB data in the Schedule Hydraulic Run View.
Area-averaged rainfall
By default, for a particular subcatchment, InfoWorks ICM assigns rainfall from the TVD connector that contains the centroid of the subcatchment.
For very large subcatchments, where the subcatchment overlaps multiple rain gauge polygons (or radar cell boundaries), using only the rain gauge polygon that contains the centroid can mean that the simulated subcatchment rainfall is not representative of the rainfall over the subcatchment as a whole.
Check the subcatchment's Use area-averaged rainfall field to calculate the rainfall for the subcatchments as the area-average of the rainfall from all rain gauge polygons that overlap the subcatchment. If the subcatchment falls wholly or partly outside any rain gauge polygon, the simulation will fail with an error during pre-processing. If the subcatchment does not have a boundary, the option is ignored.
The following variables are not area-averaged:
- Evaporation from TVD connectors
- Temperature from TVD connectors
Instead, the values used are those that would apply if using only the rainfall polygon that covers the greatest area of the subcatchment.
