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When a sigmaScaleReferenceTimeSeriesSet is configured, a vertical slider becomes automatically visible in GridDisplay to slide through the water column, displaying the 2D model results at a arbitrary water depth. The values displayed are dynamically interpolated between the sigma layers of the model, but only for the visible time step for performance reasons. The range of the slider is automatically adjusted to all available water depths for whole period, however you can limit this range using the <verticalSliderRange> option. By default 100 ticks with 10 intervals each are visible at the vertical slider. Since FEWS 2021.01 you can control the tick distance with the interval attribute in the verticalSliderRange. The direction is controlled with verticalPositiveDirection in the parameters.xml of the sigmaScaleReferenceTimeSeriesSet parameter. See for a config example Sigmalayers - display D-FlowFM 3D results in GridDisplay.
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