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.
For 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). Warning levels need not be unique. These levels are used only for level thresholds.
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).
Root element for definition of a level threshold. Multiple entries may exist.
Attributes;
- id: Unique Id of level threshold.
- name: Name for the level threshold.
Root element for definition of a rate threshold. Multiple entries may exist.
Attributes;
- id: Unique Id of rate threshold.
- name: Name for the rate threshold.
Root element for definition of a peak event threshold. Multiple entries may exist.
Attributes;
- id: Unique Id of max threshold.
- name: Name for the max threshold.
Figure 38 Elements of the Threshold configuration
Integer level used in determining icon (through ValueAttributesMap) on up-crossing of threshold (level thresholds only).
Integer level used in determining icon (through ValueAttributesMap) on down-crossing of threshold (level thresholds only).
Unique integer level defined in threshold crossing time series (internal) on up-crossing of threshold.
Unique integer level defined in threshold crossing time series (internal) on down-crossing of threshold.
Unique integer level defined in threshold crossing time series (internal) on occurrence of peak event.
Each thresholdValue links a level (e.g. 3.28 meters) to a threshold (e.g. "top of dike"). Each threshold (e.g. "top of dike") links a crossing direction (up or down) to a warning level (e.g. "Flood Alarm"). Each warning level corresponds to a unique integer that is called the severity of the warning level. Also see the figure below.
The most severe activated warning level is used for the warning icons and colours in the user interface and in the reports. Delft-FEWS takes the following steps to determine the most severe activated warning level for a given time series (the threshold log events are generated in a different but similar way).