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Posted by on Aug 9, 2015 in Blog, Sailing, Technology | 3 comments

A new perspective on iPad navigation apps

This shows how the charted islands were about half a mile off of their actual position. We were actually where the purple pin is, but the app showed us to be located on the opposite side of the island.

This shows how the charted islands were about half a mile off of their actual position. We were actually where the purple pin is, but the app showed us to be located on the opposite side of the island.


These past few days I have been rereading my own novel Wreckers’ Key, the 4th in the Seychelle series as part of the research I’m doing for the writing of the 5th in that series. That book dealt with GPS and it was written in 2006. Times certainly have changed, but I can see how that book had lots to do with my fascination with this technology. I’ve often blogged about my favorite iPad apps for navigation that make use of the built-in GPS on the iPad. Sailing out here in the Pacific has given me a new perspective on what might be my favorite app.

When I took my own boat Talespinner up and down the ICW in 2011-2012, I certainly had fun taking iPad screen shots of the times the charts showed me driving my boat across land. But most of those times, it wasn’t a big deal because I had clear visuals of the area around me, and I didn’t need to follow the charts. In fact to do so would have been nuts. Some people erroneously call this a problem with GPS. The GPS is quite accurate — it’s the charts that aren’t.

Here in the South Pacific, it can be more dangerous to rely on GPS chart plotters or tablets when the islands are often very far out of their charted positions. Many cruisers out here use a laptop navigation program using OpenCPN and they create their own charts via Google Earth that are in a file format called KAP. Our friend Rory Garland, captain of the Grand Soleil 52 Streetcar, wrote an excellent article that explains this called Google Earth navigation: how to sail off the chart with confidence using satellite imagery for the magazine Yachting World. There is now a program called Chart Aid available that makes this process a bit easier, but it does cost $99.00 for the software, and it is for Windows only.

These charts are often passed from yacht to yacht on memory sticks, and there is a good collection of them on the S/V Soggy Paws blog available for download. I happily downloaded these for the Lau Group thinking I would be able to use these on my Mac laptop as I have OpenCPN for the Mac and MacENC. However, with recent updates to my operating system, now neither one of my usb GPS devices will talk to my laptop. It does me much less good to have the charts open on the screen if I don’t have a GPS signal showing me where I am on the chart. That’s what got me looking again at iPad apps for navigation.

For the most part, Fiji charts are fairly good, but we’d heard that out in the Lau Group, we would find some gross errors in the location of the islands and also in the general drawing of the shapes of the islands. I had already downloaded the KAP files for the islands, but I suddenly realized I had no way to use them on a GPS enabled device. And when we got to the Lau Islands, we found the charts were just as bad as had been predicted. Since I like to talk about the different navigation apps, I took some shots of the differences in the views of the different apps.

Garmin chartI’ve used different iPad apps in the US & Bahamas, the Caribbean, the Med (on vacation with friends), and in the Pacific. While I prefer the Garmin Blue Chart app in the Bahamas where they make use of the excellent cartography of the Explorer Charts, Garmin’s Pacific coverage in the v2013.5 that I bought in Jan. 2014 leaves much to be desired. As you can see in the image here their cartography in the Lau islands was horrible. Compare this to the chart at the head of the blog. There is now a v2015 that I can “upgrade” to for $69.99, but I am not going to take a chance that it is still so bad.

iNavX chartThere are features of iNavX that I adore, such as the ability to GOTO a waypoint and see your DTW and ETA, etc. on the ribbon at the top of the screen. But for here in the Pacific, there are issues. I bought the Navionics Charts from the Fugawi X-Traverse site and their charts divide the world down the 180º line and don’t allow users to cross it. Fiji is bisected by that line. This means that to get from 179ºE to 179ºW you have to scroll your way all the way around the world. On the site for the current versions of the chart there is this warning: “Usage and Coverage Note: Chart regions split by the 180 degree longitude line (ex. Fiji Islands) render with portions of the regions at opposites sides of the screen with no wrap-around. Also, depth soundings are hidden within about half of degree west of 180. This is a known rendering limitation you will need to work around; it is not a problem with the chart data itself (i.e. a re-download will not resolve the issue).” The current edition of Navionics charts 50XG Australia, New Zealand, South Pacific and Hawaiian Islands cost $79.99 on the Fugawi site. At that price, this issue is unacceptable. And as we are a 3 iPad family, they only allow you to download the charts to two iPads, whereas apps that include the charts in-app allow us to buy one version of the app and share it across as many iPads as we would like.

The same issue with the 180 degree longitude line occurs with the Garmin charts.

The only navigation app I own that is able to allow users to sail across the International Dateline in their cartography is Navionics own app (pictured at the top of the page). It also allows users (through an in-app purchase) to do a satellite overlay onto the charts, and it can cache a small amount of satellite data to use offline. That Navionics app has been my favorite app for the last year or so, but I couldn’t download enough satellite data to cover all the islands we wanted to visit.

SeaIQAfter a little Internet searching, I found my new favorite iPad navigation app for the South Pacific —it’s SEAiq Open. As they say on their website, “SEAiq Open is the only vector marine chartplotter app that allows you to use your own charts on your iPhone or iPad. It supports S-57, S-63, Inland ENC, CM93, and BSB/KAP formats.” You see that last point? This app can read those KAP files that I downloaded. I bought this app for $39.99, and I was able to transfer my KAP files from my laptop to the iPad via iTunes file transfer, and presto, I had a terrific way to use these KAP files on a GPS-enabled device. The app has a very basic base map of the world, but once I got the charts loaded into the program, I simply had to zoom in on the area of the charts and I could see satellite images. Unfortunately, I didn’t take any screenshots while we were underway, but here you can see the GPS dot that shows us here at the western end of the big brown island of Viti Levu and the KAP files that knit together beautifully showing the island of Kandavu south of Viti Levu.

There is so much more that this app can do, and I look forward to using it again when we launch and get back to sailing. In the meantime, we are here in the yard slowly making progress at getting our old girl Learnativity back into shape.

Fair winds!



  1. Christine, when I first got my iPad one of the first apps I loaded was a chart plotting one. It costs about $50 and was from one of the big Blue Water type software companies. It only worked when I had a cell phone connection which is not very useful considering where most boaters like to go. I could never understand why it couldn’t function like my windows laptop in combination with Fugawi charts and an external Garmin GPS. Big disappointment.

    • Steve – I can’t diagnose what the issue was from here, but it sounds to me like you didn’t have a GPS-enabled iPad. The GPS chip is located on the same chip that enables cellular data. This doesn’t mean you have to have cellular data (we certainly didn’t have any in the screen shots I showed here) but unless your iPad is cellular data enabled, you don’t have real GPS. Instead, those iPads use a triangulation from cell towers to provide location services. Interestingly, that is another feature of this SEAiq program as it enables a wifi-only iPad to link to another device that has GPS – like a phone – and to use that GPS on the iPad. Now if only someone would create a program that would let my laptop share the GPS in my phone or iPad, then I wouldn’t have to worry about an external GPS for laptop navigation.

      • >it sounds to me like you didn’t have a GPS-enabled iPad

        I think it’s likely that this is exactly the case! The difference between location services using cellular data and “real” GPS can be a little confusing.