Most chart apps draw a straight line and leave the consequences to you. Helm plans the passage against your draft, tells you where it gets thin, and shows you when the water will be calmest before you commit to a departure.
Enter your draft once. The router treats water you cannot cross as blocked rather than as a suggestion, so the line it draws is one your boat can take. The summary reports the shallowest point on the route up front — not buried three taps deep.
The departure planner scores the next day and shows the calm windows as a simple bar. You see at a glance that the passage is comfortable from late afternoon to mid-morning and rough after that, so you leave on the right tide instead of the convenient one.
Helm explains its own plan. Rather than a mystery line, you get the legs, the course changes, and the reason a leg goes the way it does. If the router avoided something, you can see what.
Each reason is a sentence with the measurement in it, written per leg. These are the shapes they take, with example figures:
The point of putting the number in the sentence is that you can disagree with it. A detour you can see costs 1.4 NM is a decision you can overrule; a line that silently bends is one you either trust or ignore.
If a leg runs down a dredged channel and no channel condition survey has been ingested for that area, the explanation adds a line of its own accord: the depths there come from the chart rather than from a survey of the channel’s current state, so recent shoaling would not appear. A maintained channel shoals between surveys, and a router that stays quiet about which kind of number it used is the one that gets you.
A deviation gets a sentence if it is large as a percentage of the leg, or if it adds more than half a nautical mile in absolute terms. Either one triggers it. The second gate exists because of a run measured down a 19.7 NM channel: the route deviated by 1.4 NM, which was only 7.6% of the leg, so a percentage-only rule stayed silent about exactly the thing a skipper would want explained.
The router computes at chart datum, MLLW, and never adds tide to decide whether a leg is passable. Tide heights appear beside the leg as information for the hour you plan to be there, and each one is labelled with where it came from: a NOAA prediction corrected by the nearest live gauge, a published prediction on its own, or a curve computed on the device from harmonic constants when you have no signal.
A route that only works because the tide cooperated is a route that traps you when you leave an hour late. Planning at datum means the line Helm drew is one you can take at the worst water of the day, and the tide figure tells you how much easier it will be than that.
Drop and edit waypoints directly on the chart, save fishing spots and anchorages, set a home port, and annotate the chart with your own drawings. Everything syncs across your devices, so a route planned on an iPad is on the phone at the dock.
Routing is planning assistance. It does not know about a log in the channel, a shifted bar or a closed bridge. Keep a lookout and verify locally.
Yes, Helm imports GPX, so routes and tracks from another app or a chartplotter come across.
Yes. Once the chart pack for the area is downloaded, planning and navigation work without a signal.
Yes. Inland depth comes from state elevation surveys, so the router has something to work with away from the coast.
Helm Boating