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Losing GPS fix when tacking: iPhone

Jun 25, 2004
282
Hunter 306 Pasadena MD
My old C80 chart plotter is out for repair again, so after reading around on this site, I downloaded the highly recommended iSailor for my iPhone to give it a try. From a couch-view perspective, it seems like a great app. Took it sailing yesterday and I sort of balanced it in the open Navpod shell above the helm, where my plotter usually sits. All was well until I started tacking. 4 tacks in a row, the app/iPhone would lose GPS fix when I tacked! As far as I could tell, it wouldn't get the fix back again until I closed down the app and restarted it, at which point (to the app designers credit) it would pick up exactly where it left off, including the track I had started. Having had a similar problem with the C80 for years (usually losing GPS once per outing, and having to power cycle the C80 and GPS to get it back), I was sort of bummed out to have this happen again.

So I experimented by moving the iPhone away from the helm, sitting it on the seat next to me. Tacked a couple more times: no problem. The only thing I can think of to explain this is that I was sailing solo, so I used the auto tack feature on my autopilot. This causes a quick whir of the motor as it changes heading by 90 degrees or so for the tack: I guess it was EM interference when the iPhone is too close to the autopilot motor (maybe 1.5 or 2 feet away).

Anyway, has anyone else noticed this problem? I don't think it has much to do with iSailor, but more with the whole concept of using an iPhone or iPad at the helm. I've been debating whether to get a new plotter, vs. trying an iPad, but I'm not wild about the thought of the iPad having to reload the app every time it loses GPS.
 
May 17, 2004
3,420
Beneteau Oceanis 37 LE Havre de Grace
I’ve noticed that my iPhone loses GPS if I rest it against the nav pod where the chartplotter is. I assumed it was some kind of interference. The GPS chips in phones are probably designed to prioritize small size and low power over accuracy and signal reception.

There are Bluetooth GPS antennas that apps like Navionics can use as a source, so you could consider that as an alternative.
 
Jan 11, 2014
7,714
Sabre 362 113 Fair Haven, NY
iPads have their uses, but as a primary navigation device, I think 2 limitations work against it. First the screen is glossy and can be difficult to see in bright light. This can be partially remedied with a case and screen protector. However, in a case in bright sun, the unit can overheat and shut down.

Second the iPad is not waterproof or even water resistant. If things are getting wet in the cockpit, the iPad is at risk. Of course a waterproof case (I have one for my iPad) can reduce this risk, but then there are the problems with the case already mentioned.

iPads are fine for below decks monitoring and planning. B&G has an app that can mirror and control a Zeus MFD screen on the iPad. As a back up navigation device they are a less expensive option than another below deck MFD.
 
Jun 25, 2004
282
Hunter 306 Pasadena MD
I’ve noticed that my iPhone loses GPS if I rest it against the nav pod where the chartplotter is. I assumed it was some kind of interference. The GPS chips in phones are probably designed to prioritize small size and low power over accuracy and signal reception.
Interesting. Having done 3 or 4 reps of the experiment "tack ==> lose GPS fix", interference from the autopilot motor is the only thing I can think of.
There are Bluetooth GPS antennas that apps like Navionics can use as a source, so you could consider that as an alternative.
Yeah: I saw that. They seem to go for just under $100, but if paired with a cheaper (non-cellular) iPad, this might be a good alternative.
 
Jun 25, 2004
282
Hunter 306 Pasadena MD
iPads have their uses, but as a primary navigation device, I think 2 limitations work against it. First the screen is glossy and can be difficult to see in bright light. This can be partially remedied with a case and screen protector. However, in a case in bright sun, the unit can overheat and shut down.

Second the iPad is not waterproof or even water resistant. If things are getting wet in the cockpit, the iPad is at risk. Of course a waterproof case (I have one for my iPad) can reduce this risk, but then there are the problems with the case already mentioned.

iPads are fine for below decks monitoring and planning. B&G has an app that can mirror and control a Zeus MFD screen on the iPad. As a back up navigation device they are a less expensive option than another below deck MFD.
The waterproof issue certainly argues for a good case, which it seems many people use. Sailing on the Chesapeake, our plotter lives under the bimini full-time, and we do too. I think the plotter is almost never in full sun. Nevertheless, having done lots of reading on this site, I'm leaning towards an Axiom 9 at the helm, with an iPad and/or iPhone as backup. The main thing I use the plotter for (other than... plotting) is setting waypoints and transferring them to the autopilot.

Anyway, I'm sending my C80 back to the repair place in Miami for one more go (they repaired it in June with a 1 year warrantee). If they can't fix it, or if they ask for more money (saying it's a different problem, which it may well be), I'm probably going to pull the trigger on the Axiom.
 
Oct 22, 2014
15,785
CAL 35 Cruiser moored EVERETT WA
Jay, Looking at the manual again, wondering how you set your data inputs. Is this simply the iPad/iPhone and the iSailor software or are you taking advantage of the WiFi feature and including the NMEA data into the mix.

Secondly there is an issue discussed about the iOS for the apple products.
• iOS – section has only one setting for operation with the internal built-in GPS or external Bluetooth GPS via Apple iOS Location Service;
Background position tracking - switch ON / OFF the position tracking in the background mode. It’s only applicable for the (Primary PS = iOS).

There may be a priority issue when you are tacking (changing direction) that is creating a conflict for the software.
 
Jun 25, 2004
282
Hunter 306 Pasadena MD
Jay, Looking at the manual again, wondering how you set your data inputs. Is this simply the iPad/iPhone and the iSailor software or are you taking advantage of the WiFi feature and including the NMEA data into the mix.

Secondly there is an issue discussed about the iOS for the apple products.
• iOS – section has only one setting for operation with the internal built-in GPS or external Bluetooth GPS via Apple iOS Location Service;
Background position tracking - switch ON / OFF the position tracking in the background mode. It’s only applicable for the (Primary PS = iOS).

There may be a priority issue when you are tacking (changing direction) that is creating a conflict for the software.
John,
I think that all assumes I might be doing something fancy. I just installed the app, and ran it. I have "Primary PS" set to iOS, and haven't paid to "unlock" any of the other options (NMEA, AIS). I did have the background position tracking set to OFF, but I don't think the phone ever went to sleep (background mode) when the app was running. I would just come back and look at it after the tack, and it would have 0 SOG and would clearly not be tracking after the tack. Thanks for looking at the manual, though. (I did read it, although not comprehensively. It's a bit outdated.)
 
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Jun 25, 2004
282
Hunter 306 Pasadena MD
There are some well reviewed water proof tablets and this is the direction I will probably go but for now, I use my iPhone
I'm afraid I'm sort of committed to the Apple world, both phone and MacBook. If I were to get a new iPad (my wife has an ancient one), I'm pretty sure I'd be justifying the expense to my wife by telling her it's hers to use except when we're actively sailing and need a backup. Dual duty, you know... That's just thrifty. :D (No way to justify the Axiom other than "well, sailing is expensive you know, and the C80 is 16 years old".)
 
Sep 22, 2018
1,869
Hunter 216 Kingston
Just a suggestion to help “troubleshoot” whether the location of the IPhone causes the GPS lock failure would be to run a different app such as IOS maps or Google maps.
 
Oct 22, 2014
15,785
CAL 35 Cruiser moored EVERETT WA
Jay if you like the Mac on board, check out the OpenCPN software. I have been using it planing trips and am very impressed. You'll enjoy the cost of the software and the map updates. The program is professional and intuitive. I have a vesper AIS system on board and OpenCPN connects using wifi to my nmea2000 backbone where I am supposed to get GPS, AIS, and Depth.

Still in the experimenting stage, but feeling good about the land testing. Will be taking it on the water soon.
 
Jun 25, 2004
282
Hunter 306 Pasadena MD
Just a suggestion to help “troubleshoot” whether the location of the IPhone causes the GPS lock failure would be to run a different app such as IOS maps or Google maps.
Good idea. I'll give it a shot some time.

I did use Apple Maps (presumably your IOS maps) on a trip across the bay to Rock Hall a couple of weeks ago, just to get some GPS coordinates to try to reconcile some things I was seeing with the paper chart. Actually, I steered for ~12 miles to a compass heading I got from the paper chart, aiming for a small Green Can #3 which marks the southern end of Swan Point bar, an obstacle on the way to Rock Hall. Sort of an intellectual exercise, as I could just have easily buoy hopped most of the way along a channel a bit farther north, but it was fun to do the long (to me) reach just by compass heading. Made me feel sort of ... old school nautical:
chart.jpeg rock_hall.jpeg

But the way I ended up getting a track for later was with my Garmin GPS running watch. I turned it on as you would for a run, and when you get back to the internet with your phone, it overlays the track on a map. Kind of fun to have the picture, later. This was before I loaded iSailor on my phone.
 
Jan 19, 2010
9,950
Hunter 26 Charleston
I'm afraid I'm sort of committed to the Apple world, both phone and MacBook. If I were to get a new iPad (my wife has an ancient one), I'm pretty sure I'd be justifying the expense to my wife by telling her it's hers to use except when we're actively sailing and need a backup. Dual duty, you know... That's just thrifty. :D (No way to justify the Axiom other than "well, sailing is expensive you know, and the C80 is 16 years old".)
They sell some nice water proof cases for the iPad. Also some of the iPhone versions are so large they are almost a small tablet. I use navonics on my phone and really like it. 90% of the time the sonar labels in Navonics have been very close to what my depth finder shows which is a real plus when sailing in the dark on a lake with a lot of dangerous shoals. :yikes:
 
Jun 25, 2004
282
Hunter 306 Pasadena MD
Jay if you like the Mac on board, check out the OpenCPN software. I have been using it planing trips and am very impressed. You'll enjoy the cost of the software and the map updates. The program is professional and intuitive. I have a vesper AIS system on board and OpenCPN connects using wifi to my nmea2000 backbone where I am supposed to get GPS, AIS, and Depth.

Still in the experimenting stage, but feeling good about the land testing. Will be taking it on the water soon.
Thanks, John. I might give it a try. The only problem there, is how to keep the laptop charged on board. I have a small cigarette-port inverter, but a very skimpy battery bank: one normal sized starter battery, and one larger house battery (don't recall the group or amp hours). The MacBook is newer, so the battery would probably last around 10 hours, which would be enough if I could refrain from using it to read the internet at night. Which frankly, I can't. I use the iPhone as a hot spot to get the internet connection.
 
Jun 25, 2004
282
Hunter 306 Pasadena MD
That a boy. I like it.
Probably the first time I've used the chart table for its intended purpose... I've used the paper charts many times, just not the chart table, parallel rule, etc. My Dad (now passed away: Captain Sweet, USN) would no doubt be proud, as he's the one who bought all the traditional chart instruments. Not to mention the boat!
 
Jan 5, 2017
2,170
Beneteau First 38 Lyall Harbour Saturna Island
Thanks, John. I might give it a try. The only problem there, is how to keep the laptop charged on board. I have a small cigarette-port inverter, but a very skimpy battery bank: one normal sized starter battery, and one larger house battery (don't recall the group or amp hours). The MacBook is newer, so the battery would probably last around 10 hours, which would be enough if I could refrain from using it to read the internet at night. Which frankly, I can't. I use the iPhone as a hot spot to get the internet connection.
Think “Solar Panel”
 
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