Crossing an Ocean with iNavX

March 16, 2013

Note: I wrote this post in September while making passage from Vanuatu to Australia. I was all fired up about it until Vick read it and crinkled her nose (or something like that). I relegated it to the drafts folder and forgot about it until now. Recently a bunch of this year’s puddle jumpers have asked about this topic, and I figured “what the heck” I’ll just post it in case it helps someone. If you aren’t about to go blue water cruising, I suggest you give this one a skip. If you’re leaving tomorrow, and you don’t already have an iPad, likewise, skipperoo. But if you are using an iPad for navigation and haven’t already learned these tricks, I think it would be a really good idea to read this, digest it and then ask me to fill in detail for anything that wasn’t clear. Please do leave a comment so everyone can benefit from the process.

I’m an extroverted geek.  This means that a lot of people ask me about my shipboard electronics. The primary system of interest tends to be my iPad based navigation. In every case I can remember when I gave a demo, the person said something like “that is the slickest navigation system I have seen.”

It’s hard not to love anything on the iPad, desire is designed into these things. So when I talk about why I love my iPad based navigation system I try to separate out the fact that my chart plotter also plays music/games/movies, is an ebook reader (super handy for electronic cruising guides) and serves about 10 dozen other functions. In this article I will give an overview of how I use iNavX in my day to day cruising, and why I think you should too.

First the specs. I have the iPad 2 and my wife  has a first gen. iNavX works like a charm on both, but mine is our primary. My iPad has the white bezel. I prefer it over the black because it helps the device to stay cooler in direct sunlight.

I use a Brookhouse iMuxST to multiplex NMEA and Seatalk into a handy NMEA over TCP/IP stream. This is a fancy way of saying that it takes wires from my ship’s speed/depth/wind/AIS/GPS and sends them out over a WiFi network that it creates. This is super cool and if you don’t think so it’s only because I didn’t explain it well enough. This same device also allows airmail and other smart programs to pull in all of your ship’s data for it’s Position Reports or whathaveyou.

I described the setup in an earlier article and that is by and large what we have crossed five kilo-miles of ocean with.

We use the Navionics Gold charts and in fact—for world cruising—they are the only real choice. Navionics are strongly DRMd and will allow two copies per paid license, this works great for our redundancy solution (one on my iPad one on my wife’s).

I have tried other  options (openCPN, MacENC, MaxSea)  and have enough experience with them to know that they are a burden to use. The primary reason that iNavX on the iPad stands out over every other system I have seen (including Raymarine setups costing 5x as much) is the facility of the touch screen interface and the ability to quickly create, alter, and visualize routes. I won’t bore you with the details of specifically how I do all of this (though I would be happy to do a workshop at a boat show or just sit down over coffee with anyone who wants to get all hands on) but I will tell you what a typical passage workflow looks like for me…


Fact Finding

Whenever I start thinking about a potential passage, I do a port search (“where is Apia, Samoa anyway) and drop a few waypoints for start, destination and any obvious obstacles. This lets me know about how far it will be and—with a quick grib overlay—which way the wind will be blowing relative to my rhumb line. Avg time 5 minutes

Initial Plotting

As soon as I have settled on the destination and am ready to get serious I plot my way out of my starting harbor, and into the destination harbor by dropping consistently named waypoints (e.g. TNGFI 1,2,etc. for the Tonga to Fiji passage) after each waypoint is set a simple tap tap allows me to add them to the end of the current route. Avg time 15 minutes (for a 500 mile passage)


I download gribs twice a day and iNavX has a passable grib overlay so that you can see the wind and swell direction and strength right on the charts. This deserves an article of it’s own but it’s perhaps a bit too dry to feature here. It’s also one of the places that iNavX could improve. Regardless it’s part of every planning workflow and takes… Avg time 2 minutes

Pre Trip

Prepare for new Tracks

Export old tracks. INavX has a maximum cache size for tracks that is just big enough for a 800 mile passage on low res. If you remember to clear it before passage it also gives a useful average speed and miles traveled statistic. I don’t do this until I am underway in cases where there is a tricky pass at the start of my passage. Avg time 2 minutes

Cache Satellite Imagery 

Download and cache satellite images for passes and obstacles, and compare them to the chart to ensure accuracy. I do this by going to an area that I want to verify and dropping a waypoint. Then I tap that area and select Map from the menu. iNavx will then download the satellite image and show my waypoint as a pushpin. When I wanted to verify that a pass was where I expected it to be. I would drop a pin on either side of the pass and then check to see if the satellite showed the reef in the same spot.

During Passage

Fine Tuning

I expect to start changing my route as soon as we get underway. Once I know the reality of the wind direction and speed I can make fine adjustments to our course including my favorite pastime, tack planing. iNavX makes it too easy to draw angles and measure distance right over your route. As a result I tend to plot two, three or even four tacks with a fairly high degree of accuracy. In addition to giving me much more accurate trip time and time to waypoint data it has been a great tool for illustrating my intentions to the crew. I do a lot of this during night watches and all my wife has to do is glance at the screen when she comes up and ask any questions. Having a visual aide really helps to facilitate clear communication when I’m exhausted after a watch . Avg time 10 minutes per tack (most of that time is my inability to do math without using my finger

24 Hour Time

I drop a waypoint every 24 hrs and add that to my route. We love our stats and 24hr time has been our favorite benchmark. iNavX takes all the sting out of this and actually makes it fun. I just scroll through the tracks, find the one that corresponds to my starting time (0100 UTC in this case) and tap the “create waypoint” button. Avg Time 2 minutes if I have a lot of track points to scroll through.

I also use the measure tool to figure a rough Miles Made Good. Avg time 5 seconds

Course Correction

On this passage to Fiji I had several possible routes to choose from. I left port fairly certain that I would take the Oneata Pass route but as soon as the wind resolved, I changed my mind (several times) and decided on the southern route. Even then there were about 3 possible ways to weave between the islands and reefs. I was grateful to have a quick way to duplicate a route and make changes. Later when I decided that the older route would work better, I just tap tapped and my route changed with my whim. Avg Time 1 minute. The cached satellite imagery really helped here too.

One huge benefit of this effort is super accurate trip time and time to waypoint estimates. iNavX brings the love by doing all the math for me, I get Distance to Waypoint, Time to Waypoint, and ETA at waypoint, and the same for the destination. I can guess time of arrival to within a half day at the outset of our passage, assuming the wind does what is forecasted. By mile 250 of a 500 mile passage I can usually estimate our ETA with ±3 hr accuracy. This is awesome information to have under any circumstances but it is beyond awesome when you need to time your arrival at a pass, port, or other rendezvous.


I am going to switch gears now and talk about the cons for a bit. By far my biggest disappointment has been the way Navionics handles the Anti-meridian (AM) on it’s Pacific Charts. There is just no conceivable (to me) reason why these charts should not center on 180° longitude. They don’t though, and that means that when you sail across the AM you have to do a lot of painful kludging. As a result you age faster and die sooner. I’m not kidding Navionics, you are killing me here. Some of the pain that this needless oversight inflicted was:


Routes decide to bounce off the AM sending the dotted route line the long way around the world. This is just lame. At least it doesn’t mess with the distance calculations, but it means that I have to drop extra waypoints at 179° 59.99′W and 179° 59.99′E. You will never see the E waypoints because the text is on the wrong side of the AM and doesn’t render. This does allow you to see if there is an island on the other side of the AM that you would run into immediately after crossing that imaginary line (which was a real problem for our passage)

A tip for other iNavX users for dealing with the AM issue. The Chart button at the bottom of your screen with center on your yacht. Also the Tonga/Fiji chart will show the same detail as the SE pacific charts and for a while (until you get close to the AM) they will remember the last position that they were focused on. So if you turn off “Pos Icon Loc.” you can quickly flip back and forth.

Another antimeridian related problem was that vector lines stopped working on infinite. I use this all the time to paint a helpful line showing where I am expected to go. Close to the AM it just stopped working. Lame.

Areas for Improvement

  • Every once in a while iNavX doesn’t get a packet from the multiplexer in time. This triggers an alarm which wouldn’t be such a big deal except for the fact that it clears my goto and I have to go through the 4 step process to set it all back up again. Not a biggie except when it happens 4 or 5 times in a row, or during a pass.
  • On that note it would be sweet if iNavX would allow me to click on a waypoint and set it as the next goto in route rather than the kludgy way I have to do it now.
  • The gamma shift Night Mode (that reddens everything) is great but it would be nice if I could turn it on from the Charts screen rather than having to go all the way back out to Preferences.
  • Even better if it could come on automatically when the ambient light dipped to darkness. Likewise it would be nice to have an additional dimmer effect inside iNavX, as the iPad doesn’t get quite dark enough to preserve my night vision.
  • iNavX caches a certain amount of Google Maps for overlays. This is insanely useful for planning to shoot passes. It would be stellar if it could give me a cache size adjustment and a way to tell how full my cache is so I can plan more effectively. Right now I have to cache as much as I think I will need (starting with the least necessary so that it will drop off the cache first) and then go offline to see if I got it all.
  • It would also be awesome to be able to tune the cache size for tracks, and better to be able to save and load tracks locally so that I could go back and refer to my tracks later. This has been an issue recently when I wanted to give someone waypoints for a pass and had to go through a lot of unnecessary technical massaging to get the answer.
  • I would also love to be able to delete a selection of track data in bulk so that my anchor track doesn’t ruin my passage making speed average… for instance.



In spite of these annoyances, I still strongly recommend this setup for other cruisers. The fact that iNavX has been responsive and proactive in introducing new features and bug fixes only reinforces my high opinion. Other than the one Anti-Meridian issue, the Navionics charts have been amazing and though I wouldn’t recommend shooting a dangerous pass on charts alone, I have used them in conjunction with the awesome satellite overlay feature to plan a successful night time passage through a 1 mile wide pass here in Fiji. Unlike some other electronic charts, Navionics reduces resolution when it doesn’t have accurate information, so it is clear that the charts shouldn’t be used to navigate.


  1. Comment by Cidnie

    Cidnie March 16, 2013 at 7:43 pm

    Ridiculously helpful. Thank you!

  2. Comment by Justin

    Justin March 17, 2013 at 1:33 am


    Great post. We’ve been following you since before you left, courtesy of Michael & Sara on Wondertime. My wife went to high school with Sara. We’ve had the same positive experience with iNavX and the iPad/iPhone in general for navigation and onboard email. I’m sure you know, but didn’t mention that iNavX can overlay AIS which is extremely useful too.

    After reading your detailed descriptions of your routing process, I thought I’d mention there are now two free/very inexpensive onboard weather routing options that I bet you’d really enjoy. One is PC based and the other is an app. This is could further simplify your route planning, especially for ocean crossings, and improve your ETA even more. Coincidentally, I just wrote about the two options yesterday on our blog at In the end you can have an “optimized” route in iNavX and carry on from there just like you’ve been doing. Something to tinker with over the winter or summer or whatever they call it down there. 🙂

    • Comment by Tucker Bradford

      Tucker Bradford March 17, 2013 at 3:43 am

      I love weather routing apps. I played around with MaxSea TimeZero on the Pacific Crossing and found it to be a lot of fun in port, but totally unnecessary at sea. I’m going to check out your article and try the apps for sure, because I’m geeky that way, but I would warn those who are new to weather prediction and routing to do as much by hand in the early stages as they can. It taught me to know what to expect and be suspicious when the software worked but had the wrong data, or didn’t work correctly.

      I also forgot to mention in this article that I used a really cool paid app called iRegatta to record my polars. This is really important for those users who will want to do advanced weather routing in the future.

      Anyway, thanks a ton for your comment. I’m sure it will be as useful to the other readers as it was to me!

  3. Comment by Rona House

    Rona House March 17, 2013 at 5:21 pm

    Great for planning but I’m still using a Garmin on deck which is easier to see in bright light and less of a personal disaster if I break it! Time will tell in 2014 if I can’t find cheap Pacific charts for the Garmin….
    I did notice in Fiji the 180 meridian could break your course inconveniently between East and West

  4. Comment by Lauri

    Lauri March 20, 2013 at 2:41 pm

    where does a person get a brookhouse imuxst? i googled it and got zilch.

    sv Ashika
    currently in P.V., heading south tomorrow.

  5. Comment by Parker nichols

    Parker nichols January 1, 2014 at 1:34 pm

    Hello and thanks for the great info about Inav-x. My wife and i will be cruising the sea of cortez this winter and i am interested in purchasing the Inav-x package to use on our ipad along with our paper charts. Problem is that i am NOT a computer-tech type so feel i could really use some training. Any idea if there are any good online training classes on computer based navigation software?

    Thanks so much.
    Parker nichols

    • Comment by Tucker Bradford

      Tucker Bradford January 19, 2014 at 5:04 am

      Sorry for the slow response. I don’t know of any such training, but I would be happy to answer questions here. It’s very straight forward too and you can learn it incrementally. The most important features could be written up in a few blog posts (which might be a good idea anyway), I remember the online documentation being fairly good and easy to read too!

  6. Comment by Jason Anderson

    Jason Anderson February 7, 2014 at 1:05 pm

    I’m currently running an old Garmin as my primary chart plotter because it’s easy, and I’ve already purchased the local charts. As we prepare for our cruise, I’m exploring nav options.

    I also run iNavx on my iPhone, mostly as a portable gps when I’m out in the dinghy exploring. I own an iPad and would happily invest in an iPad system and relegate my current garmin to backup, except I’m lacking radar. For just about the same price as a cheap standalone unit from another manufacturer, I can get a basic garmin chart plotter/radar with basic world maps.

    It appears that I’m kinda stuck, and I’m guessing the cost is a wash overall. Any ideas or thoughts?

  7. Pingback: Electronic charting on Estrellita: iPad, iNavX and Navionics ~ SV Estrellita 5.10b

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