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DELFT-FEWS supports checking of time series against thresholds. When thresholds are crossed, appropriate messages may be issued. Definition of thresholds is in two parts. In the first part of the configuration, the types of threshold used are defined. In the second, the values for threshold valid for a particular location and time series are defined. In this section the configuration for the definition of the thresholds is defined. DELFT-FEWS supports different types of threshold events. These include crossing of level and rate thresholds. The occurrence of a peak is also seen as a threshold event.Thresholds are defined in two files: thresholds.xml (described here) and thresholdValueSets.xml (described here). The first file contains definitions of threshold groups with thresholds and the types of threshold. There are three types of thresholds: level crossing thresholds, rate of rise and fall thresholds and max value thresholds. For a given threshold the options that are independent of location and parameter are defined.  Additional threshold options for specific locations and parameters are defined in the thresholdValueSets configuration file.  It is possible to configure one or more threshold groups.

ThresholdGroup

A threshold group is a collection of one or more thresholds. The groups can be used to apply multiple threshold for displaying in graphs. Each group can contain any number of level thresholds, rate thresholds and max value thresholds. For each threshold group it is possible to define a default threshold. The default provides extra information for the state in which no thresholds are crossed. The state in which no thresholds are crossed always corresponds to the least severe warning level in the thresholdWarningLevels configuration file. The least severe warning level is used e.g. to get the color to display in the user interface when no thresholds are crossed.

Level Threshold

A threshold that triggers a threshold event if a certain level is crossed upwards or downwards. For this type of threshold it is possible to configure an upWarningLevelId or a downWarningLevelId. There are also options to configure upIntId and downIntId, both of which are deprecated and should not be used when making new configurations.

upWarningLevelId:  Optional id of a warning level that will be activated for a particular location and parameter if a data value is above this threshold.

downWarningLevelId: Optional id of a warning level that will be activated for a particular location and parameter if a data value is below this threshold.

Warning levels are defined in the thresholdWarningLevels configuration file. If no warningLevels are defined, then this threshold will not activate any warningLevels to be displayed, but it will still generate threshold crossing events for both upward and downward crossings.

upIntId: DEPRECATED, do not use in new configurations. Id that will be put to the output time series if a particular threshold value of this type is crossed upwards. This id must be unique through this file. If not specified, then this id will be generated automatically.

downIntId: DEPRECATED, do not use in new configurations. Id that will be put to the output time series if a particular threshold value of this type is crossed downwards.

Similar to the Id's used, a warning level integer can be assigned to threshold crossings. This warning level is resolved to either an icon (for display in the main FEWS GUI), or a colour (for use in reports or schematic status displays). Warning levels need not be unique. If not specified this id will be generated automaticallyFor each threshold defined, two additional items need to be configured. Internally DELFT-FEWS maintains threshold events as a non-equidistant time series, where the crossings are identified by an integer. For each threshold two unique integer Id's need to be assigned. One ID is used to identify the upcrossing of the threshold, the other Id is assigned to identify the downcrossing. The exception to this is the peak threshold where only a single Id needs to be assigned to identify the occurrence of the peak event. Note: in the new thresholds configuration approach (thresholdGroups) these ids are optional and will be generated when not specified in configuration.

Similar to the Id's used for upcrossings and downcrossing, a warning level integer can be assigned to threshold crossings. This warning level is resolved to either an icon (for display in the main FEWS GUI), or a colour (for use in reports or schematic status displays). Warning levels need not be unique. These levels are used only for level thresholds.

Configuration

When available on the file system, the name of the XML file for configuring the types of thresholds is for example:

Thresholds 1.00 default.xml

Thresholds                                 Fixed file name for the Thresholds configuration

1.00                                            Version number

default                                       Flag to indicate the version is the default configuration (otherwise omitted).

levelThreshold

Root element for definition of a level threshold. Multiple entries may exist. 

Attributes;

-         id: Unique Id of level threshold.

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