TurboRouter includes unique routines for calculating port-to-port distances. Instead of using static distance tables that are hard to keep updated, TurboRouter calculates the distance between any pair of ports. This is done by calculating the shortest (great circle) distance between the ports that does not intersect any land contours. Experience shows that the calculated distances are far within the requirements for this type of planning tool.
The red line in the screenshot illustrates the shortest distance calculated by TurboRouter between two ports.