The general calculation settings is a list of possible settings one can use in a tidal window calculation that determine the accuracy of the calculation.
The general calculation settings is a list of possible settings one can use in a tidal window calculation that determine the accuracy of the calculation.
- Time location granularity: the discriminating power of the root finding algorithm. It states that possible safe or unsafe intervals shorter then this value will probably not be found. This is mostly set to 15 minutes, which is equal to the minimum route width.
- Time location precision: the precision of the root finding algorithm. If a root is found, then it is investigated with the bisection method up to this precision. Mostly it is set to 2 minutes, which gives an average error of 1 minute.
- Reliability: the percentile that is taken from the normal distribution of the calculated chances of touching the bottom touches. With a 95\% percentile, the chance of a type 1 error (indication that a time location is safe, while it is not) is at most 5\%.
- Wave height variation for wave spectra selection: the variation that should be applied to the given swell to select possible wave spectra. A value of 0.05 indicates that when wave spectra are sought around 120 cm swell, then PROTIDE randomly selects wave spectra with swell heights between 0.95 * 120 and 1.05 * 120.
- Number of wave spectra to select: the number of wave spectra that are selected to pass to OCTOPUS for one given swell height.
- Wave direction mean: the mean wave direction passed to OCTOPUS as the direction the swell waves collide with the ships in the channel
- Wave direction standard deviation: the standard deviation of the swell wave direction
- Number wave direction iterations: the number of different draws from the wave direction distribution.
- Wave direction spread: the directional spread of wave energy OCTOPUS should use around the given swell wave direction. The cosine power should be passed. Thus, 2 means cos2 and 8 means cos8. Typically 8 is passed for swell.
- Cut off value cross current exclusion: the amount of cross current a ship can handle while entering the harbor. This is the maximum value (in m/s) component of the water speed / direction that is orthogonal to the channel angle.
- Damp current factor inside harbor: the factor that the water speed is damped, when the ship is inside the harbor. 0.75 means that 75\% of the current speed is damped inside the harbor, so 1 m/s is damped to 0.25 m/s
- Damp waves factor inside harbor: the factor that the swell is damped, when the ship is inside the harbor. 0.6 means that 60\% of the swell height is damped inside the harbor, so 80cm of swell is damped to 32cm