You are viewing an old version of this page. View the current version.

Compare with Current View Page History

« Previous Version 9 Next »

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.

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.

-         name: Name for the level threshold.

rateThreshold

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.

maxThreshold

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

upWarningLevel

Integer level used in determining icon (through ValueAttributesMap) on up-crossing of threshold (level thresholds only).

downWarningLevel

Integer level used in determining icon (through ValueAttributesMap) on down-crossing of threshold (level thresholds only).

upIntId

Unique integer level defined in threshold crossing time series (internal) on up-crossing of threshold.

downIntId

Unique integer level defined in threshold crossing time series (internal) on down-crossing of threshold.

intId

Unique integer level defined in threshold crossing time series (internal) on occurrence of peak event.

Some notes that explain how Delft-FEWS handles thresholds

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.

Definitions
  • If a threshold only has an upWarningLevel or has upWarningLevelSeverity > downWarningLevelSeverity, then the threshold is called an "upCrossing threshold". This means that the threshold activates its upWarningLevel when there are data values above it (e.g. flood warning).
  • If a threshold only has a downWarningLevel or has downWarningLevelSeverity > upWarningLevelSeverity, then the threshold is called a "downCrossing threshold". This means that the threshold activates a warning when there are data values below it (e.g. drought warning).
  • If a threshold has upWarningLevelSeverity = downWarningLevelSeverity, then the threshold is called both an "upCrossing threshold" and a "downCrossing threshold". This means that the threshold activates its upWarningLevel if there is data above it and/or below it. It does not make sense to have upWarningLevelSeverity = downWarningLevelSeverity, but this is possible in the old thresholds configuration (not in the new improved thresholds configuration).
  • A thresholdValue with an upCrossing threshold has been crossed when there are data values above or equal to its value.
  • A thresholdValue with a downCrossing threshold has been crossed when there are data values below or equal to its value.
  • A thresholdValue with a threshold that is both upCrossing and downCrossing has been crossed when there are data values above, below or equal to its value, i.e. always.
Determination of most severe activated warning level

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).

  1. First Delft-FEWS finds the thresholdValueSet (V) that corresponds to the given time series. If there is no thresholdValueSet defined that corresponds to the given time series, then no warning levels are activated, i.e. "All clear".
  2. For the given time series only the data within a given time period is used. The TimeSeriesDialog and DataEditor use the period that is currently visible in the chart. The explorer user interface uses the relativeViewPeriod defined for the timeSeriesSet in the Filters configuration file. The ThresholdEventCrossingModule uses the relativeViewPeriod defined for the timeSeriesSet in the ThresholdValueSets configuration file. The ThresholdOverviewDisplay uses the configured aggregationTimeStep or relativePeriod in the ThresholdOverviewDisplay configuration file. Please note that in the ThresholdOverviewDisplay and in the Reports the data is read using the timeSeriesSets configured in the inputVariables. Therefore the relativeViewPeriods defined for the timeSeriesSets of the inputVariables must include the relativePeriod for which the most severe activated warning level has to be determined. Otherwise not all of the required data is read.
  3. If the given time series contains only missing values, then no warning levels are activated, i.e. "All clear".
  4. For each data value separately, Delft-FEWS considers each levelThresholdValue in V and determines if it has been crossed for the given data value (see above for definitions of crossed). Each levelThresholdValue that has been crossed, activates its corresponding warning level. From all the warning levels that are activated for the given data value, the most severe warning level is chosen. This is repeated for each data value within the given time period. From the resulting warning levels for the individual data values, the most severe warning level is chosen.
  • No labels

Disclaimer