The channel path (between start of the channel and the berth), the kilometer positions and the harbor angle form the relevant information of the harbor/channel for the tidal window calculation.
Channel path
Depending on the direction of the planned voyage (inbound or outbound) and the berth a channel path is constructed. The channel path is a collection of channel segments with the characteristics depth (NGD or nautical guaranteed depth), angle (the inbound direction of the channel; 0 degrees is north, 90 degrees is east, et cetera) and the channel bottom elevations (positive deviation relative to the NGD).
Kilometer positions
The channel path also has knowledge on the kilometer positions relevant for the calculation. A kilometer position is the distance via the channel between a location and the 0-kilometer position. The 0-kilometer position is defined by the border between open sea and the inner harbor. All kilometer positions in open sea are positive and are negative for the inner area. For a tidal window calculation the kilometer positions consist of all integer kilometer points plus the (possible fractional) end points and significant positions. These significant positions are manually added to guarantee safety at critical points and are listed in the final tidal window report.
Harbor angle
For the cross current calculation the average angle is determined of the segment(-s) at the 0-kilometer position, which we call the harbor angle. In a later part of the calculation the component of the water current that is orthogonal to this harbor angle is defined as the cross current.
