Passage Maker - - Contents - Dag Pike

Safety Mea­sures with a New Tech

Car nav­i­ga­tion has never been eas­ier since the in­ven­tion of sat­nav sys­tems. Just feed in the zip code and the sys­tem knows where you are and where you want to go, and presents a suit­able route. Now, some nav­i­ga­tion apps such as Waze are even crowd­sourc­ing data so that the nav can sug­gest al­ter­nate, faster routes in the event of road­way ac­ci­dents or work slow­downs. Why not do the same with our chart plot­ters? Out at sea, there are no de­fined tracks ex­cept in chan­nels and har­bor en­trances, mak­ing your A-to-B route more of a free-form ad­ven­ture. The depth of wa­ter can be re­stric­tive, and there can be other no-go ar­eas on or un­der wa­ter that may limit the cho­sen route so the com­puter can­not work its magic.

Garmin, pi­o­neers of road nav­i­ga­tion, in­tro­duced their au­torout­ing sys­tem for chart plot­ters many years ago. Like the land­based sys­tem, you sim­ply en­tered start and fin­ish points on the chart plot­ter, and the sys­tem would find the route au­to­mat­i­cally. Now, elec­tronic chart provider Navion­ics has de­vel­oped an au­torout­ing sys­tem that does much the same thing. The Garmin sys­tem is limited to use on their own branded plot­ters, of course, but Navion­ics does not make plot­ters, just elec­tronic charts, so their sys­tem has been adopted by many of the elec­tronic play­ers, such as Ray­ma­rine and the Nav­ico Group, which in­cludes Lowrance, Sim­rad, and B & G. With the com­pe­ti­tion heat­ing up, it is time to look at what these au­to­mated sys­tems can and can­not do, in­clud­ing an­a­lyz­ing the risks of let­ting the elec­tron­ics take over your pas­sage plan­ning.

Hav­ing your route planned au­to­mat­i­cally would be fine if the seas were not lit­tered with ob­struc­tions to nav­i­ga­tion. These days, cruis­ers have to cope with traf­fic sep­a­ra­tion schemes, oil rigs and plat­forms, and now the first wind farm in U.S. wa­ters in Long Is­land Sound. In ad­di­tion, there are the nor­mal prob­lems of avoid­ing rocks, shoals, and shal­low wa­ters. Nav­i­ga­tion has be­come com­pli­cated and the ques­tion asked was, “Could auto-rout­ing cope with all of these chal­lenges while still pro­vid­ing a safe course?”


Both of the sys­tems tested al­low you to in­put the draft of your yacht as well as other pa­ram­e­ters, such as mast height (for bridge clear­ances), beam (for canals and locks), and tol­er­ances for how close to the dangers you want to pass. As for draft, you don’t want to in­put your ex­act draft be­cause the sys­tem takes this fig­ure lit­er­ally: give your­self plenty of wig­gle room to be sure to avoid un­nec­es­sary ground­ings. Mast height and beam only ap­ply to in­land wa­ters and canals, but the dis­tance off dangers seems to be a bit ar­bi­trary. This only ap­plies with the Garmin sys­tem and is de­fined by words like close and dis­tant. If you are go­ing to de­fine this pa­ram­e­ter, then it would be help­ful to have it as a mea­sure­ment, such as ¼-mile. With auto-rout­ing, it is up to you to de­fine the safety mar­gins and you have to re­mem­ber that these two sys­tems do not take into ac­count the rise and fall of tides when con­sid­er­ing safe wa­ter depths.


Un­less dangers to nav­i­ga­tion are marked on the elec­tronic

chart, auto-rout­ing will ig­nore them. There could be ar­eas of strong tidal currents that you might want to by­pass, but you are un­likely to see these on elec­tronic charts. The in­creas­ing nav­i­ga­tion re­stric­tions posed by off­shore oil in­stal­la­tions and wind farms will only be taken into ac­count if they are dis­played on the chart, which re­quires you to have the lat­est charts in­stalled. Off­shore oil in­stal­la­tions and wind farms make life dif­fi­cult for many Euro­pean boaters, and are steadily in­creas­ing the num­ber of no-go cruis­ing ar­eas.


Let’s look at how the two sys­tems cope with plot­ting spe­cific routes. This re­view is not a di­rect com­par­i­son be­tween the two sys­tems but a look at how the sys­tems cope with a va­ri­ety of chal­leng­ing routes. We were limited by the charts avail­able for the two sys­tems, which were the North­east and North­west for Navion­ics and Florida and the Ba­hamas for Garmin. In se­lect­ing the plot­ted routes, we tried to pro­vide a va­ri­ety of chal­lenges to auto-rout­ing, in­clud­ing sail­ing from ma­jor ports, cross­ing traf­fic sep­a­ra­tion zones, sail­ing along ship­ping chan­nels, deal­ing with wind farms, and mak­ing land­fall.


To start, a route was plot­ted from Mi­ami Beach Ma­rina to a port on Marathon Key. There are three op­tions when mak­ing this pas­sage:

1) The in­side chan­nels which are lit­tered with shoals and bridges.

The Garmin sys­tem chose the last of these three, prob­a­bly ig­nor­ing the in­side chan­nel be­cause of the many shal­low-wa­ter patches. We en­tered 10 feet as a safe draft, and this might have been the rea­son that the in­side/out­side chan­nel was re­jected. If I had been nav­i­gat­ing, I think I would have cho­sen the sec­ond op­tion that some­what avoids the strong cur­rent that pours up the Straits of Florida when you go out­side.

The pro­posed course made a dog­leg out of the ma­rina and headed down the mid­dle of the chan­nel com­ing out of Mi­ami Har­bor. Then it made a sharp right turn to pass in­side the spoil ar­eas. Af­ter that it plot­ted a route that I would have con­sid­ered dan­ger­ous, pass­ing in­side the buoys that mark the var­i­ous shoal patches that ex­ist along this shore. In some cases the routes passed close to shoals where there was no marker buoy, such as Pick­les Reef. The plot­ted route passed near to these shoal patches, much too close for com­fort, as far as I was con­cerned. To fol­low this route you would be to­tally de­pen­dent on the ac­cu­racy of your GPS, with no mar­gin for er­ror. Around Key Largo, the pro­posed route took a more in­shore line be­tween shoal patches, and then to­ward Marathon, the rout­ing took the buoyed chan­nel west of Pi­geon Key Banks be­fore turn­ing east to­ward the mari­nas at Marathon.

To be sure, it was a tough route to plot, so the next one we asked it to con­fig­ure was more straight­for­ward: head from Mi­ami across to Nas­sau, Ba­hamas, the route fol­lowed by many boaters. This is a fairly straight shot across the Florida Strait from Mi­ami, and then Garmin’s auto-rout­ing soft­ware rec­om­mended a voy­age around the north­ern end of North Bi­mini, fol­low­ing a track to pass close to the north side of the un­marked Moselle Bank rather than tak­ing a more in­side route to pass the marker on North Bank. From there, it sug­gested cross­ing the Flats, pass­ing close to the North West Shoal and then on to Nas­sau. In Nas­sau Har­bour, the route skirted the cruise-ship ter­mi­nal and the shal­low wa­ter in or­der to ar­rive at the ma­rina. Apart from that chan­nel north of North Bi­mini, this was a pretty safe route to fol­low as long as you had func­tion­ing GPS to en­sure safe pass­ing of some of the shal­lows.

Sum­ming up, you would need to do a lot of fine-tun­ing to make sure you had a vi­able route with the Garmin sys­tem, and you would need to check out the route in con­sid­er­able de­tail to en­sure safe pass­ing dis­tances for many dangers.


For Navion­ics, we threw in some ar­eas with traf­fic sep­a­ra­tion zones which have strictly gov­erned rules about what you should

and should not do in these ar­eas ac­cord­ing to the Col­regs. You have to cross sep­a­ra­tion chan­nels at right an­gles and if you are un­der 20 me­tres in length, you should try to keep out of them al­to­gether. Over that length, you have to use the chan­nels, but be­cause Navion­ics does not re­quest your boat’s length, the sys­tem does not know. In fact, it ig­nores these routes, ex­cept to flag up a warn­ing triangle to show that you should be aware. The Garmin sys­tem also ig­nores these traf­fic zones.

The route from Seat­tle to Vic­to­ria on Van­cou­ver Is­land is lit­tered with traf­fic sep­a­ra­tion zones, but the sys­tem com­pletely ig­nored them and took the straight-line, short­est route avail­able. Al­though the plot­ted route dis­played a mul­ti­tude of cau­tion­ary tri­an­gles, I would have opted for a route closer in­shore, away from ship­ping lanes and only crossed them at right an­gles on a cou­ple of oc­ca­sions rather than zigzag­ging in and out of them. This auto-plot­ted route would have re­quired a lot of ad­just­ment and quite frankly it would have been a lot eas­ier just to start from scratch, and plot the whole thing man­u­ally.

A sec­ond route was plot­ted from Mon­tauk, Long Is­land, to Sun­set Lake on the north­east­ern cor­ner of Martha’s Vine­yard. This route, once again, ig­nored traf­fic sep­a­ra­tion zones head­ing into Rhode Is­land (apart from the warn­ing tri­an­gles). There was also one point where the route chose to pass in­side a chan­nel marker buoy with no ad­van­tage in the dis­tance cov­ered. Al­though rel­e­vant to the dis­cus­sion (but not to this ex­am­ple), the new wind farm to the south of Block Is­land was dis­played on the chart.


These tri­als showed that auto-rout­ing has a way to go be­fore it pro­vides a com­pletely trust­wor­thy sys­tem of pas­sage plan­ning. On rel­a­tively sim­ple routes where there are no or very few re­stric­tions, it works rea­son­ably well, but the al­go­rithm used is not geared to cop­ing with traf­fic sep­a­ra­tion zones and has trou­ble deal­ing with chal­leng­ing routes. Both sys­tems ig­nore sep­a­ra­tion zones, and un­less you cor­rect the course man­u­ally, you are sub­ject to ar­rest by the Coast Guard for vi­o­lat­ing the Col­regs. It is also ev­i­dent that any pro­posed route re­lies heav­ily on hav­ing ac­cu­rate GPS po­si­tion­ing be­cause the clear­ance from dangers can be quite small. Our route down the Keys passed much too closely to dangers for my lik­ing. I plot­ted an ad­di­tional route in Euro­pean wa­ters that took me right across a shoal where the chart did show enough wa­ter, but that shoal was noted for its con­stantly shift­ing depths.

Both sys­tems will of­fer you a route into and out of har­bor, di­rectly into your ma­rina berth but quite why you should need auto-rout­ing in buoyed chan­nels I am not sure. In buoyed chan­nels it is pretty clear where you need to be and auto-rout­ing does not keep you to the star­board side of the chan­nel. In open seas, auto-rout­ing might have some merit by of­fer­ing a ba­sic route around which to start plan­ning.

The dis­play makes it quite clear that the pro­posed routes are not to be used for nav­i­ga­tion with­out de­tailed check­ing and dou­ble-check­ing. You do not want to fol­low it im­plic­ity.


These tri­als showed that auto-rout­ing has a ways to go be­fore it pro­vides a com­pletely trust­wor­thy sys­tem for pas­sage plan­ning.

48 pas­sage­maker.com March 2017

2) The in­side/out­side chan­nels, which fol­low closely along the Keys and then out­side them.

3) The fully out­side pas­sage, which takes you clear of all in­shore dangers and shoals.

Navion­ics dis­play show­ing the over­all route from Puget Sound to Vic­to­ria. In my es­ti­ma­tion, greater care should be taken in cross­ing ship­ping lanes at 90- de­gree an­gles.

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