Tablet Navigation on the ICW

14 Jul


July 12, 2019

There has been a sea change in small craft navigation over the past few years. Today boats circumnavigating the globe with a tablet as their chartplotter. For those of us cruising the ICW the changes are no less revolutionary!   The impact of tablet navigation apps will affect cruisers differently based upon their experience, their existing navigation tools, and the cruising grounds.

Most ICW cruisers have an installed chartplotter.   Tablet navigation allows you to scan the area ahead and around you looking for new options and destinations, while the chartplotter continues to provide your location.

Your chartplotter will be using charts based upon some flavor of NOAA charts.  Some chartplotter charts are easy to update, and many are not. Tablet systems are also based on the NOAA charts but are more easily updated.  In the ICW, up to date charts, a calibrated depth finder, and stabilized binoculars are essential equipment.

Adding tablet navigation provides you with a chartplotter repeater and a secondary chart system. Beyond that, a tablet is more than adequate as a supplement to the chart plotter. Were they more weatherproof they would replace the chartplotter. We have tried nearly a dozen navigation apps.  Aqua Map and Navionics are the two we find to be the best. The Aqua Map and Navionics apps each have their own strengths and weaknesses.

NOAA paper charts

The federal government has been creating paper charts since 1807. The responsibility for today’s charts falls on NOAA. Their chart catalog contains thousands of charts.  Of interest to ICW cruisers is the 220 charts which cover the route of the Atlantic Intracoastal Waterway (AICW or ICW). Due to increasingly tight budgets, NOAA no longer has the funding to survey most of the coastal waters and byways, instead, they focus their data collection on the ports and shipping channels needed for interstate and international transport.  Today, the best up to date chart bathymetry is available through Navionics Sonar Charts (crowdsourced bathymetry) and Aqua Map Master which has the NOAA bathymetry overlaid with USACE surveys in many shipping channels and most of the ICW inlet crossings.

Tablet Navigation

The tablet navigation apps (Including cell phone apps) offer many options.  You may not need to utilize all the options depending upon what your existing systems are capable of and how you use them. With tablet navigation, it is very easy to create and modify a route. There are more iOS apps  available than Android apps today, but new Android apps are in the works  We have used quite a few tablet apps and are now using two apps Navionics and Aqua Map Master

  • Tides and currents are device resident and stations are visible on the chart and can be “animated” to show forecast current and tide on a date/time slider.
  • Can easily send and receive tracks and routes with other cruisers and
  • With an appropriate onboard WiFi system the tablet will share inputs from the navigation network. (Varies with the app and the navigation equipment.)
  • Easily transportable device to share and compare notes with other cruisers.
  • Easy update of all NOAA charts in your library
  • Creating routes is simple. You create a route manually by tapping on the screen.
  • Includes Active Captain data overlay
  • Charts are economically priced.
  • As a tablet app, it is virtually “instant on” and it can be ruggedized with the right case to provide splash protection.
  • Canadian charts are available a separate subscription.
  • Bahamas charts are available with separate subscription or purchase with updates forever


We have used the Navionics app in parallel with our PC navigation and Raymarine chart plotter  Coastal Explorer for the past 4 years and 22,000 nautical miles.

  • Navionics is 3 charting systems in one app.
    • NOAA Charts.
    • NOAA Charts with Navionics’ special sauce.
    • Navionics Sonar Charts (NSC). Crowdsourced bathymetry built on top of the NOAA charts.
  • Easy, rapid update of all NOAA charts in your library, or any individual area of the coast.
  • Sonar charts have been getting better and better and overall are more accurate than NOAA bathymetry They offer excellent detail of the bottom contours.
  • Auto routing. After setting your boat parameters, with two touches of the screen, you can plot a route for the day (limited to a set number of waypoints) or to an upcoming bridge or lock to get your ETA.  Just tap on your destination and a route fitting your boat’s parameters. You can then adjust your speed and desired to arrive on time.
  • Easy to create a route or play “what ifs” should you decide to change your destination.
  • Exchange GPX routes and tracks with Raymarine, Lowrance, Simrad chart plotters when fitted with the Navionics chart chip.
  • With access to internet (cell phone or shore WiFi ) can display wind and weather.
  • The Canadian charts are available. In our experience, the Navionics sonar charts are superior to Canadian Hydrographic (CHS) charts. They are far more detailed and better than the CHS charts.
  • Bahamas charts are available. Navionics uses Wavy Line The Sonar Charts are gaining accuracy and details in the as more and more boats cruise the Bahamas with a Navionics chart chips in the plotter.
  • The NSC charts cover a far wider area than the USACE surveys. There are many thousand channels, creeks, anchorages and harbors which are not surveyed by USACE and the NOAA depth data may be very old and out of date.
  • Can be integrated with your boat’s network, to display AIS targets
  • The sonar charts are being continually updated, but in any given location you do not know when the bathymetry was most recently updated.
  • Does not support split-screen multitasking.

Aqua Map and Aqua Map Master

We started using Aqua Map in January 2018 in anticipation of a trip through the Rideau Canal in Canada.  With a separate subscription, Aqua Map has digital copies of the CHS (Canadian Hydrographic Service) charts.

  • Aqua Map charts are NOAA Charts with Aqua Map updates 4 times per year
  • With Aqua Map Master ($10/yr subscription) you will have the ability to overlay the US Army Corps of Engineers color-coded hydrographic surveys on the chart. These surveys cover shipping channels and High traffic channels along the ICW and some interconnected waterways.
  • Each USACE survey is dated. You know when the data was collected.
  • ICW statute miles are clearly labeled and are searchable/sortable by distance from current location (What Statute Mile marker are we at now?)
  • Excellent anchor drag alarm.
  • With the Master subscription, you can also connect the app to your boat’s NMEA network
  • Each USACE survey has a date. You must always check the survey date to be sure it is not old and no longer current.
  • The USACE surveys only cover a very narrow track in the most heavily traveled corridors. At times in the ICW there is deeper water adjacent to but outside the area covered by the USACE survey. There are many channels, hundreds of creeks, harbors and anchorages which are not USACE surveyed.  The NOAA chart depth readings are often far out of date and wrong
  • With the Master subscription, you can also connect the app to your boat’s NMEA network
    • Each USACE survey has a date. You must always check the survey date to be sure it is not old and no longer current.
    • The USACE surveys only cover a very narrow track in the most heavily travelled corridors. At times in the ICW there is deeper water adjacent to but outside the area covered by the USACE survey. There are many channels, hundreds of creeks, harbors and anchorages which are not USACE surveyed.  The NOAA chart depth readings are often far out of date and wrong
    • With the appropriate onboard WiFi gateway.
      • Can display AIS targets Configurable alarms for dangerous AIS targets. Requires an AIS receiver on the boat?
      • Can display wind and depth info on the app
      • There is a “Route Explorer” that will check your routes for potential hazards along the way, potential bridge interference, and fuel options.
    • Active Captain Integration
    • Waterway Guide Integration
    • If connected and it has access to depth data, it will record that along with your tracks, so you can later go back and see what actual depth was at any point along the time-stamped route ( You will need to manually adjust to derive MLLW).
  • Can establish an online account at company (GEC) website which will allow you to use app/maps on up to 5 devices, as well as have an online repository of you data (tracks, waypoints, GPX files) to sync across your devices. Screen refresh is slow on PTZ and panning if you want to look ahead to your destination.
  • There is no “auto route” as on the Navionics however it does provide look ahead feature to alert you to Waterway guide alerts and active captain information as you go along your route.

Our navigation and piloting on the ICW have evolved. In the past decade, we have cruised 32,000 nautical miles.  In that time, we have;

  • Used PC navigation 32,000 miles
  • 22, 000 miles with Navionics Sonar Charts
  • 12,000 with Raymarine chartplotter
  • 10,000 miles with Aqua Map.

While our use of electronic navigation tools might seem excessive, it has allowed me to compare a variety of different tools as new ones come available.  We started with tried and true PC navigation and  we have evolved from there.  For cruising the ICW today, a good, calibrated depth finder (We prefer the fish finder display!)  is essential. This is a game of inches. You must be sure that when the depth finder says 6’ it really is 6 feet.  Only the Navionics Sonar Charts and Aqua Map Master USACE surveys can provide up to date chart depth information which is essential along parts of the ICW.

New Jersey coast

For many cruisers, the ICW voyage actually starts in New England or Canada.  So, for these boats, transiting the New Jersey coast is necessary.  One very handy anchorage mid-coast is Barnegat Inlet.  As with any ocean inlet, you do not want to attempt to enter during the peak of the ebb current cycle.  Not only will you be facing 3+ knots of current against you, but the standing waves can be huge! This situation is exacerbated by the prevailing onshore ocean swells from the southeast.  IF the entrance looks ferocious, it is best to wait offshore till the ebb current drops.

Barnegat Inlet is a useful example of how important it is to have more than NOAA based charts. The screenshot below is the NOAA chart of this entrance.  It is rather difficult to plan your approach on the NOAA chart, in this case, presented in Aqua Map Master app. My NOAA charts in the chartplotter are identical to this.  You’ll notice that none the less there are two tracks for us as we entered and exited this inlet. We created those tracks as we piloted our way using Navionics Sonar Charts.

NOAA Chart 12324 Updated though 7/13/2019

The screenshot below shows our track entering Barnegat inlet from the south.  We found the reported depth on these crowd-sourced charts to be quite good. (We’ve transited this inlet 4 times in 3 years.) Without the advantage of Navionics Sonar Charts, you could enter this inlet by following the USCG aids to navigation (ATONs).  But wait, the NOAA charts have none of the channel ATONs!

In the screenshot below, I have displayed color marked depth gradations.  This is a feature you set up on your own. For our use the reds are 5-6 feet, yellow is 7-8 feet.  Teal is 9-10 feet Purple is 11-14 feet.  This option makes it very easy to follow the Sonar Charts into this inlet.  NOTE: there are no charts which are perfect.  The Sonar Charts have proven to be very good: in many cases (such as this entrance) they are clearly superior to NOAA charts.

South of Fernandina

The image below shows the detail offered by Navionics Sonar Charts.  We picked our route northbound in March of 2019  based upon the charted depths shown on Sonar Charts.  We have taken this route 10 times in the past 5 years. The first time through here we had scouted it with the dinghy and created a route using Sonar Chart Live.  At that time, the chart bathymetry was so out of date that in November 2014 it appeared that we ran over dry land for nearly a mile: we were in 12+ feet of water. The track through here is what is known as the “western” track.

The screenshot below shows the same track on the same day using Aqua Map Master. The east-west portion of this chart is covered by the USACE survey.  It very clearly shows the deepest water.  These surveys are of great value along the ICW. The north-south portion is the NOAA chart.  In one area where NOAA shows 5.9 feet, the Sonar Chart and our depth finder indicate 14 feet. Also note that G1B shown on Navionics is not shown on the NOAA chart.

In the screenshot below, I have colorized the Navionics Sonar chart.  It quite clearly shows the shoal in the middle of the river south of G1A and a 7-8 foot shoal growing out towards G1A which, is handy information as you approach that point

The following two screenshots are the latest information (July 12, 2019)on one of the most changeable inlet crossings on the ICW, Lockwoods Folly.  The channel was dredged in early April 2019.  By June it was already showing trouble.  The first chart is the Navionics Sonar Chart.

The screenshot below is the Aqua Map Master chart displaying a USACE survey of mid-June 2019.It clearly shows a shoal building into the recently dredged ICW just east of G47a.

On it are displayed two routes.  The pink route is the route created in Aqua Map based upon this USACE survey.  The black route was made in, and transferred from, Navionics. WP73c is an Aqua Map waypoint it is about 35’ off the tip of the new shoal depicted in the USACE survey. WP448 is a waypoint from the Navionics route.  It would be helpful if the USACE June survey was a little wider as Navionics shows that there is 10-15 feet of water north of WP73c where the USACE survey of January 2019 shows only 3-4 feet. The June 2019 survey used in conjunction with the Sonar Charts  might  lead one to assume that there is 12 feet of water 100 feet north of WP73c

Each app does seem to steer you past the shoal, though the AMM route is perhaps more precise and accurate, the  NSC route does keep you in 7+feet MLLW.  The obvious question is how much precision is useful, as it is pretty difficult to stay directly on a route through an inlet crossing. To be 30 feet to one side or the other of either route here would be pretty fair steering?

In conclusion, both Aqua Map Master with USACE surveys, and Navionics with Sonar Chart crowd sourced bathymetry are excellent programs.  Although we have run the east coast from Florida to New England many times with the Navionics charts, having access to the USACE surveys adds another layer of useful content for route planning.  Coming north in the ICW in the spring of 2019 we were glad to have access to the USACE surveys (USACE does have a significant delay in updates post dredging.  We transited this section just after the dredge completed the work and was still onsite: the surveys were not updated for several weeks. )  I am very surprised and disappointed to see how quickly the Lockwoods Folly channel has silted.  Clearly, boats travelling the ICW must have charts with updated depth data, not available on the standard NOAA issued charts. Navionics is providing chart updates almost continuously so you will want to take advantage of any new information.  All boats headed south this winter would be well advised to have both of these apps.




  1. Preston

    Great article and very detailed. Loved it. Question for you….

    In the Navionics IOS App, how did you turn on the “color marked depth gradations” feature. Looks to be very helpful but I don’t see anywhere in the app to do that as you describe…

    “Red for 5-6 feet, yellow for 7-8 ft etc”

    I have also emailed Navionics with the same question but that may take a while to get an answer.

    Headed down the AICW in a few days from MA to FL

  2. Steve

    Please disregard my previous comment. I now see why these images appear different. Thanks for the excellent article.

  3. SAIL the ICW

    We have no experience With Bad Elf GPS, but many others have found them to be an excellent GPS receiver. All three of our iOS tablets are “cell capable”. That means that they could be used as cell phones. But they are not. None of them have a cell plan. But if you have a “cell capable” device, it has to have the GPS chip in it to comply with national 911 rules. The WiFi only tablets do not have to have a GPS chip .

  4. John

    Nice article. Have you had any experience with a Bad Elf GPS unit using your tablet? I am considering buying a Bad Elf GPS so I use it with the iPad app and am curious if it tells speed, etc.

  5. Pete W.

    ….”WP37c is an Aqua Map waypoint it is about 35’ off the tip of the new shoal depicted in the USACE survey. ”

    Should this [and subsequent references] read “WP73c”? I see this twice, but I don’t see “WP37c”.
    Nonetheless, this is a Very informative article; I need to upgrade, for sure.

  6. Jody Argo Schroath

    Well put, Tom! And I appreciate the way you’ve used the depth-color feature to such excellent effect. A problem, as you note, occasionally arises with recent but pre-dredge USACE soundings in even more recently dredged trouble spots. The same applies to pre-dredge soundings. Knapps Narrows on the Chesapeake is a prime example.

  7. john

    What a great article!! Well researched and presented. This will help many people. If I may, I suggest that you use grammarly or some such software to help polish your writing. Thanks again

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