The input of the transformation is two time series. The first one contains the times of the astronomical high or low tide. The values are not the levels, but the tide number. The second input is a continuous time series that contains water levels. This can be a forecast, an observed or hindcast series.
The transformation will use the time steps of the astronomical tide number input, and it will search for peaks in the continuous time series around each of those times.
For every timeStep of the continious series the slope of the data curve is determined. A minimum or maximum is found if the slope is horizontal (thus the value of the angle is 0). If the slope value changes from positive to negative, it is a maximum, if it changes from negative to positive, it is a minimum.
There are two output time series: both are non-equidistant, the time steps are the times of the actual high tide. The values in one are the tide numbers, in the other the water level.
A peak is valid if:
1. There is a value within the search window both before and after the maximum where the difference between the peak and the value is greater than the validDifferenceExceedence. The value before the peak is called firstThresholdValue in this method, the value after the peak is called the secondThreshold value.
2.Missing values are not allowed between the peak and the two threshold values.
If a missing value if found after the peak and before the second threshold, the peak is automatically invalid.
Config example:
<transformation id="SelectionTideNumbersAndPeaks">
<selection>
<selectNumberedTidalPeaks>
<numberedTidalPeaks>
<variableId>numberedTidalPeaks</variableId>
</numberedTidalPeaks>
<continuousLevelSeries>
<variableId>continuousLevelSeries</variableId>
</continuousLevelSeries>
<minutesBeforeTidalExtreme>50</minutesBeforeTidalExtreme>
<minutesAfterTidalExtreme>50</minutesAfterTidalExtreme>
<regressionPeriodInMinutes>20</regressionPeriodInMinutes>
<validDifferenceExceedence>0.02</validDifferenceExceedence>
<highWaterLevelOutput>
<variableId>outputTideValue</variableId>
</highWaterLevelOutput>
<highWaterTideNumberOutput>
<variableId>outputTideNumber</variableId>
</highWaterTideNumberOutput>
</selectNumberedTidalPeaks>
</selection>
</transformation>
See more information in:
