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 the Great Lakes, the US Army Corps of Engineers publishes them for the inland rivers, and anyone can have them. Nobody owns that data and sells it back to you.
Helm builds its charts from that data and reprocesses it into its own packs. 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. Charts, chart pack downloads and route planning are free to use. The subscription is $99.99 per year after a free trial.
NOAA has retired its traditional chart products. The PDF charts, the raster navigational charts (RNCs) and the BookletCharts were cancelled chart by chart, and the last of them went in December 2024. Links to charts.noaa.gov/PDFs, /RNCs, /BookletCharts and the old OnLineViewer pages now return an error or a retirement notice, so many club resource pages and older articles point at nothing.
The chart data itself did not go away. NOAA now publishes it as electronic navigational charts (ENCs), and these are the official places to get it:
| If you used to use | Go here now |
|---|---|
| PDF charts and BookletCharts, to print or keep on a tablet | NOAA Custom Chart: pick any area and scale and it makes a printable PDF chart from current ENC data. How it works. |
| The online chart viewer | NOAA ENC Viewer, in a web browser. |
| RNC files for chart software | NOAA ENC downloads, the vector files most chart software now reads. |
| Why the change happened | NOAA's notice: Farewell to traditional nautical charts. |
If you would rather have the same NOAA data on your phone, offline and with the charted depth read against your boat's draft, that is what Helm is for. The rest of this page explains how it works.
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. Helm reprocesses that data into its own chart packs, which are not an official NOAA product.
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 used and what CATZOC means 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 |
|---|---|
| Charts | NOAA electronic navigational chart data, public, reprocessed into Helm's chart packs. Rivers come from the US Army Corps of Engineers Inland ENC. |
| Offline charts | 161 downloadable chart packs. They sit on your device and are yours to keep there. |
| 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, with a subscription, 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 and bearing along any line you draw, and the shallowest point along it in the coastal and Great Lakes packs that carry routing data.
Depth comes from the chart itself, and where a NOAA tide station is within 25 nautical miles, Helm adds that station's predicted tide so the number moves with the water. The depth card also says what kind of figure you are reading: a charted sounding, a depth band from the chart, or water the chart has no soundings for. Where the depth comes from is a page of its own.
The inland rivers come from the US Army Corps of Engineers Inland ENC, which carries depth. The state lake packs draw lakes and reservoirs by name and shoreline from the USGS National Hydrography Dataset, and Minnesota adds state contour lines on its lakes. 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 where the chart carries depth, routing in the coastal and Great Lakes packs that carry it, 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. Trips you run with Go on a route are recorded to the logbook, and routes, saved spots and recorded trips sync between your devices once they are signed in to the same account.
Helm is free to download on iPhone and iPad, and its charts, chart pack downloads and route planning work without a subscription. Its charts are built from NOAA chart data, it reads the charted depth against your boat's draft, and it works offline from 161 downloadable chart packs.
Yes. Helm builds its charts from NOAA electronic navigational charts, the same public data NOAA publishes for United States waters, reprocessed into its own packs, and adds the NOAA CO-OPS predicted tide to the charted depth where a station is close enough.
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.
NOAA retired them; the last were cancelled in December 2024. The closest replacement is NOAA Custom Chart, which makes a printable PDF chart of any area from current ENC data. The full list of replacements is at the top of this page.
No. NOAA publishes electronic navigational charts as public data for United States waters. Helm reprocesses them into its own chart packs for offline use.
No. Helm runs on iPhone and iPad, natively on both, and with a subscription 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 where the chart carries depth, routing in the coastal and Great Lakes packs that carry it, the measure tool and the anchor alarm all run from the device.
Both. Coastal water and the intracoastal come from NOAA charts, and the inland rivers from US Army Corps of Engineers charts. Inland lakes and reservoirs are shown by name and shoreline from the USGS National Hydrography Dataset, and Minnesota also has state depth contours drawn on its lakes.
Helm Boating