The official charts for United States waters are public data. NOAA's Office of Coast Survey publishes electronic navigational charts for the coast, the intracoastal and navigable rivers, and anyone can have them. Nobody owns that data and sells it back to you.
Helm reads those NOAA charts directly. The app is free to download from the App Store, the chart packs come down to your own device, and there is no chartplotter, no plug-in card and no separate chart purchase between you and the water.
Free to download. 3-day free trial, then $99.99 per year.
An electronic navigational chart is the official chart, in vector form. The soundings, depth contours, buoys, beacons, obstructions and channel limits come from NOAA's own survey and charting work, and they carry NOAA's scale and quality information with them. It is the same data a commercial vessel navigates on.
NOAA publishes it openly and keeps it current on a rolling basis: a buoy moved off a shifting bar, a newly charted obstruction, a revised channel limit all arrive as chart updates. Because the data is public, a chart app does not need to license a proprietary chart set before it can draw your harbor. Helm builds its chart packs straight from what NOAA publishes. The detail of how the ENC data is read and what CATZOC adds is on its own page.
A lot of the cost of getting a chart in front of you has historically been hardware and per-region chart products. On a phone that is already in your pocket, most of that disappears.
| What you need on the water | Where it comes from in Helm |
|---|---|
| Official charts | NOAA electronic navigational charts, public data, read directly by the app. |
| Offline charts | 161 downloadable chart packs. They sit on your device and are yours to keep there. |
| Depth surveys | USACE eHydro dredging surveys and state lake elevation data, both public sources, merged in. |
| Tides and currents | NOAA CO-OPS predictions against the MLLW datum, with current arrows that turn with the time you scrub to. |
| Hardware | None. It runs on the iPhone and iPad you already own, and on CarPlay on the tow to the ramp. |
Helm is free to download and includes a free trial. The App Store page shows current pricing for your region: Helm Boating on the App Store.
Public chart data is the starting line, not the finish. NOAA publishes the numbers; what you want on the water is an answer. Helm does that work on the device.
Enter your boat's draft once. Helm shades the water your boat cannot cross and plans routes around it, so a run from the marina out to the inlet bends around a shoal instead of drawing a straight line over it. The measure tool returns distance, bearing and the shallowest point along any line you draw.
Depth comes from four sources merged into one reading, with the date the measurement was taken: the NOAA chart, USACE eHydro dredging surveys, state lake elevation data and the live tide. A channel dredged last spring reads with the survey that describes today's bottom, not with a chart sounding from another era, and Helm shows you which is which. How the four sources merge against your draft is a page of its own.
Lake depth comes from state elevation surveys rather than the NOAA chart, which is why a reservoir in Texas or Tennessee is charted water in Helm with real contours on it. Rivers and maintained channels pick up the Army Corps surveys as well. There is more on lakes, rivers and the intracoastal.
Coverage is divided into 161 downloadable chart packs. You take the water you actually run and leave the rest. With the pack on the phone, the charts, the depth shading, routing, the measure tool and the anchor alarm keep working with no bars at all, which is the ordinary condition offshore and a few hundred yards from most lake ramps. Downloads run in the background and resume if they are interrupted. See how the offline packs work.
Underway, the same data feeds the strip along the bottom of the chart: depth, speed over ground and course over ground in one place, with the anchor alarm a tap away, nearby vessels on AIS, and satellite and night chart styles on hand. Every trip is recorded to a logbook you can replay later, and routes, markers, tracks and the logbook sync across your own devices.
Helm is free to download on iPhone and iPad and includes a free trial. It runs on official NOAA charts, merges four depth sources against your boat's draft, and works offline from 161 downloadable chart packs.
Yes. Helm reads NOAA electronic navigational charts directly, the same public data NOAA publishes for United States waters, and layers USACE eHydro dredging surveys, state lake elevation data and the live NOAA CO-OPS tide on top of them.
Start with the phone you already own. The NOAA chart data is public, Helm is free to download with a free trial included, and there is no chartplotter, no plug-in chart card and no separate chart purchase on top of it. Current pricing is on the App Store page for your region.
No. NOAA publishes electronic navigational charts as public data for United States waters. Helm reads them directly and packages them for offline use.
No. Helm runs on iPhone and iPad, natively on both, and puts the chart on the vehicle's screen through CarPlay on the way to the ramp.
Yes. Download the chart pack for your area and the charts, depth against your draft, routing, the measure tool and the anchor alarm all run from the device.
Both. Coastal water, the intracoastal and navigable rivers come from NOAA charts. Inland lakes and reservoirs come from state elevation surveys, so they carry contours and a depth reading rather than a blank outline.
Helm Boating