Navigation and Communication

(Posted 10/28/2016)


Since I first went to sea over four decades ago, no aspect of sailing has undergone a more radical change than navigation.  The days of celestial navigation have largely been replaced by GPS, electronic chart plotters, AIS, wifi, and so forth.  As with all other aspects of our preparations, we've tried to keep the complexity of our electronics to a minimum while hopefully keeping abreast of the most essential offerings of marine electronic technology. 

As amazingly accurate and convenient as electronic navigation is, we ultimately trust none of it without a solid backup and therefore have a sextant, nautical almanac, sight reduction tables and several accurate time pieces.  Our sextant is a simple plastic Davis Mark 3, our sight reduction tables the somewhat primitive H.O. 211, but I've made numerous landfalls with that combination in years past, so am confident of it as a backup.

We have two handheld GPS units (Garmin Geko and Garmin Colorado C), both of which we'll use as backups. 

Our primary navigation though will be via a tablet (Samsung Galaxy Tab A) with internal GPS, and a smartphone (BLU 8XL), also with internal GPS.  Both of these are Android machines onto which we've downloaded the chart plotter program Open CPN for Android.  This is a relatively recent release and an excellent navigation app.  For anyone interested in the chart plotter, it's available on Google Play.  Note that two versions are offered there.  The version of Open CPN for Android by Dave Register is the one we have, and the only one with support.  Dave's response to questions on the OpenCpn for Android forum is quick and thorough. 

With the navigation hardware and software in place, we turned to locating and downloading electronic charts.  Without going into endless detail, there are basically two types of electronic charts.  One is raster, which is an electronic representation of the paper charts us old timers grew up with.  The other is called ENC, an acronym for 'electronic navigation charts'.  Each type has its pros and cons.  Personally, I prefer raster charts as that's the format I'm more familiar with.  ENC charts though, take up much less storage space, so those are mostly what we've downloaded.  ENC charts also have many features that can be shown or hidden with the click of a button.   

All U.S. coastal waters are covered by  NOAA charts that can be downloaded in either format for free.  Charts for the South Pacific take some searching.  The cruising site Soggy Paws has many Pacific charts available for free (thanks!), as does the government of New Zealand.   

Once the charts are downloaded, the internal GPS shows one's position on the chart.  It's all pretty slick.  So much so in fact that it's easy to be lulled into a sense of complacency by the ease and convenience of it. 

Not only can this system show you where you are with amazing accuracy, but with the addition of another electronic gizmo called an AIS, almost all other marine traffic in your area will also show up on the chart.  That includes freighter, tankers, cruise ships, commercial fishing vessels and, increasingly, pleasure craft.  AIS stands for automated identification system.  An international regulatory body requires essentially all ships and passenger vessels to carry an AIS transceiver, which transmits a continuous VHF (very high frequency) signal that the AIS transceiver on another vessel can receive.  The signal shows the name of the transmitting vessel, its position, speed, course, draft, destination port and most importantly, its CPA, or closest point of approach.  For those of us with smaller vessels, a much less expensive option is to have an AIS receiver, which allows us to 'see' vessels with transponders, although they cannot see us.

Adding somewhat to the complexity of the system is the possibility of adding a wireless antenna to the AIS receiver.  The antenna then broadcasts the AIS information wirelessly throughout the boat.  The advantage is that a cable isn't required between the AIS and the tablet or smart phone or whatever the chart plotter is loaded onto.  The other advantage is that the AIS information can be seen on more than one device at a time. 

The importance of AIS can be seen by going to, a website that shows the location in real time of most vessels on the world's oceans.  Zoom in on an area of the the chart to see marine traffic.  The volume of shipping coursing up and down the coast in busy shipping lanes such as between the Panama Canal and Los Angeles is an eye opener for any small boat sailor. 



Communication-wise, we'll have two hand held VHF radios that have a strictly line-of-sight range.  Our primary use would be to contact ships that the AIS indicates would be passing uncomfortably close.  They will also be useful for contacting other boats anchored with us in harbors along the way.  

We're considering a satellite phone, mostly to send blog updates while we're at sea.  The expense of the unit and ongoing connection costs are the downside.  We're still pondering this one.

We may also have a short wave and single side band receiver, mostly for catching news and other broadcasts during night watches.  

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