Route Planning Needs Current Vectors

Current has direction.

For route planning, that direction decides whether the current helps you, slows you, or pushes you sideways. A two-knot current with the route is a gift. A two-knot current against the route is costly. The same current across the route can create drift and steering correction.

HECTOR's routing work treats current as a vector because that is what the boat experiences.

Speed Alone Is Misleading

If a route planner only sees current speed, it cannot tell whether the current is useful.

The effect depends on the angle between the current and the course. It also depends on wind angle, boat speed through water, and whether the boat can make progress on the desired leg.

A fast route is not always the shortest line.

It is the route with the best combination of wind, current, depth, and timing.

Interpolation Has to Respect Direction

Current direction is circular.

You cannot average 350 degrees and 10 degrees as if they are ordinary numbers. The correct result is near north, not south. Vector interpolation avoids that mistake by converting direction and speed into east/north components, interpolating those, then converting back.

That is technical, and it prevents real route errors.

Cross-Current Changes the Boat's Path

A current across the intended course creates drift.

The boat may need to steer a different heading to maintain the desired track. In stronger flow, a direct leg can become inefficient or impossible without correction.

Route cost needs to account for traversal behavior, not just distance.

Good Routing Explains Waits

Sometimes the best route is not a different line.

It is waiting for a better current window.

If a tidal gate is unsafe now but improves in two hours, the planner should be able to explain that. Waiting is a route decision, not a failure.

This is where weather routing becomes more human: not just "go there," but "go when the water lets you."