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NOAA ENC Charts

NOAA electronic navigational charts are free vector charts -- depths, buoys, hazards, and coastline -- that you download once and use offline. They sit alongside your satellite imagery on the navigation page.

What ENC charts are

Satellite imagery shows you what the ground looks like. An ENC chart shows you what the chart says: charted depths, contours, soundings, buoys and lights, wrecks, rocks and obstructions, restricted areas, and the coastline. They're vector data, so they stay sharp at any zoom and take far less space than raster imagery.

The app describes them as: Download free NOAA electronic charts for offline navigation -- depths, buoys, hazards, and coastline.

Not a substitute for official charts

These are downloaded from NOAA and rendered by Bristol Maps. Rendering and updating are on our side, not NOAA's. Keep your required paper or type-approved charts aboard.

Getting there

Offline Maps tab, then tap the NOAA Charts button at the top of the page. The Search bar filters regions instead of imagery while you're on this tab.

Browsing regions

Charts are downloaded a region at a time. The catalog covers 16 regions in five groups:

Group Regions
Alaska Bristol Bay, Prince William Sound, Cook Inlet, Southeast Alaska, Western Alaska
West Coast Pacific Northwest, California
East Coast New England, Mid Atlantic, Southeast US
Gulf of Mexico Gulf of Mexico
Great Lakes Great Lakes
Islands & Territories Hawaii, Puerto Rico, Guam, American Samoa

Each region is a card with its name, a description of what it covers (Bristol Bay reads "Naknek, Kvichak, Nushagak, Togiak, Ugashik"), and a status line.

A gold Your area tag marks the region the app thinks you're in, based on your position or your settings. On a first run with nothing downloaded, a banner at the top says You appear to be in region with a one-tap Download region charts button.

Card status

Status Meaning
Not downloaded Nothing on the device for this region
n cells ยท n features What you have downloaded

Buttons on each card, shown as they apply:

Button What it does
Download Fetches the region's charts
Update (n) Applies pending updates -- the number is how many cells need one
Delete Removes that region's charts from the device

If you have downloaded cells that don't match any catalog region -- from an older version, say -- they appear in an Other downloads group where you can delete them.

Downloading

Tap Download on a region. The app fetches the NOAA product catalog first ("Fetching NOAA catalog...") then downloads the cells for that region, showing a progress bar and a running count.

A Cancel button stops it. Cancelling is safe: completed cells are kept, and picking it up later resumes rather than starting over.

The catalog is a big file

The NOAA product catalog is about 52 MB of XML. Bristol Maps streams it to disk rather than holding it in memory, and caches it for 24 hours -- so a second download within the same day skips the fetch. Give the first one a moment on a slow link.

Download on Wi-Fi

Chart downloads are large. Do them on Wi-Fi in town, not on satellite or cell.

Keeping charts current

Above the region cards you'll see how many cells you have downloaded and, underneath, Last checked with a date and time.

Check for Updates asks NOAA what has changed. You'll get one of:

  • All charts are up to date.
  • A count of what needs updating, which you then apply per region with the Update button on its card.
  • Could not reach the NOAA catalog. Try again later.

Automatic chart updates

Under Chart display options there's a switch for Automatic chart updates, subtitled Checks weekly, Wi-Fi only.

With it on, the app checks about once a week and applies updates on its own -- but only over Wi-Fi. Automatic chart traffic never goes over a metered satellite or cell link. It also holds off while you have a download running of your own, and it only does anything if you already have charts downloaded.

Wi-Fi only is deliberate

If you're offshore on satellite the whole season, automatic updates will not run. Check manually next time you're on Wi-Fi.

Display settings

At the top of the NOAA Charts tab:

Setting Description
Display NOAA ENC charts Master switch for drawing charts on the navigation page
Opacity Slider from 0 to 100

Open Chart display options for the per-feature switches:

Setting Description
Depth areas Shaded depth zones
Depth contours Charted depth contour lines
Minor contours The finer contours between the major ones
Depth soundings Individual charted sounding numbers
Coastline The charted shoreline
Land areas Land fill
Buoys Charted buoys
Lights Charted lights
Wrecks Charted wrecks
Obstructions & rocks Charted obstructions and rocks
Restricted areas Charted restricted areas

Two steppers control when the busiest features appear:

Setting Range
Soundings min zoom 8 to 16
Contours min zoom 6 to 14

Raise these if soundings and contours clutter the screen when you're zoomed out; lower them if you want detail sooner.

Draw above imagery

A switch with the subtitle Off: charts sit under your satellite imagery.

Leave it off and your satellite imagery stays on top with the charts underneath. Turn it on and the chart draws over the imagery -- useful when you want the buoys and soundings readable over a dark image, at the cost of hiding the ground.

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