As default the statistics are based directly on the time series values themselves, i.e. relative to zero.
However, for a time series file it is possible to give any constant reference level which is substracted from the time series values before the statistics are calculated.
Another possibility is to give the reference level as a time series covering the whole period. In this way it is possible to compute statistics on e.g. the difference between a simulated and a measured time series in water levels, i.e. on the error. In addition you can specify a lower and upper reference level limit. In this case only time steps for which the reference level is inside this range gives a contribution to the statistics. Thus, if only a minimum reference level is given and the time series are again water levels, statistics on the error during periods of high level can be calculated.
Note: Delete values in the file are not considered when calculating statistics. E.g. you can have an exceedance percentage of 100 percent, even if the grid point is not flooded at all time steps.
