Navionics on I-pad

[Flagman101]

Hello, I just came back from a Charter in the Grenadines and was issued a I-Pad with Navionics instead of have a real dedicated charter plotter.
I did not mind as I have Navionics for my boat and works well in the area I sail.
My boat is in Montreal, on lake Two mountains.

Sailing in the Grenadines is not lake sailing. I experienced confusing information form Navionics.

Sailing toward Tobago cays coming from the north east of Canouan
I know there is a reef to avoid before i can turn toward Tobago cay.
I look at the I-Pad to steer a proper course that will put me east of the reef.
The red course line displays was pointing way off of my real course. It pointed west of the reef.
From a distance i could see the breaking waves on the reef and knew from experience that i was sailing to the east of the reef.
So I ignored the i-pad.
Getting closer I look at the iPad and it was now displaying my position and course correctly.
Weird.
I had similar issues sailing to petit Martinique between Palm Island and Union.
The iPad was showing me right over the reef near Frigate Island but physically we were at least a quarter mile west of it.

Also leaving Tobago cays, sun was reflecting of the water and prevented me from seing the reef from a distance.going north, again the same reef. I steered according to the iPad.
Ended up so close to the reef I had to take evasive manoeuvres because i felt i was way too close even if the iPad displayed me as being in the clear.


Ended up using the iPad just to measure distances before getting going and to get my SOG.

The rest i felt I could not trust or just confused me.
I know these areas very well and could manage without a chart plotter.

In the end I'm not sure using an iPad and Navionics is a good alternative to a more expensive dedicated chart plotter.
I wonder if others have experienced similar problems.
Was it just this particular iPad?
One thing for sure, it was a good thing I was sailing familiar waters as I would have run aground if I did rely on the iPad for navigation.

[bensolomon]

You are obviously a smart and prudent sailor. I gave up on Navionics for similar issues. I now use iSailor by transas. I only have an iPad as my chart plotter. I have not had any nav issues with isailor. Disclaimer:. I always plan and plot my courses using paper charts, using the iPad as a guide. There's much to be said for doing what you did.......looking around and trusting your instincts.

[Flagman101]

Originally Posted by bensolomon

You are obviously a smart and prudent sailor. I gave up on Navionics for similar issues. I now use iSailor by transas. I only have an iPad as my chart plotter. I have not had any nav issues with isailor. Disclaimer:. I always plan and plot my courses using paper charts, using the iPad as a guide. There's much to be said for doing what you did.......looking around and trusting your instincts.

I do look at paper charts. I plan my trip with them and memorize obstacles etc.
But a proper chart plotter is very useful and fast for final approaches.
I don't need a chart plotter until I am very close.
The Grenadines have splendid clear waters and reefs can be spotted easily. But it scares me to think if I had been in a destination where water is murky. Or just unknown to me.
Since I'm an hired skipper on charter boats, i get all kinds of different equipments.
I have never had issues before. But the next charter that provides only an iPad with Navionics...I will have to have a talk with the charter company before setting off with clients

[MV Wanderlust]

We used Navionics on an iPad on our boat successfully for a year. On one occasion, it did show us so far off course that it put us about 150 yards on land. After a quick reboot of the iPad, it was fine. From that point on, we rebooted it every day before departing and it was always spot on after that. Could have been your issue. Or maybe it was something else entirely.

[Privilege]

I apologize if this an overly-basic question but did the iPad have GPS installed; ie; was it SIM compatible?

Mine isn't and so I only use it for practice. If close to land it works off the local towers and gives me a fairly accurate location. Once I get a mile or two out, it starts guessing my location.

[jkleins]

You really haven't ever experienced a GPS problem before? I have noticed them several times on my dedicated GPS receiver and I fully expect that the GPS on the iPad will as well although so far so good (knock wood). I always approach using GPS coordinates as a navigation aid as if they could go wonky at any time although it is rare enough that I do get complacent and don't always DR the way I should. I am pretty good at making sure the nav aids and the GPS/ Chartplotter are all showing the same thing when around stuff I can hit but I do worry that one of these days I will get too used to this electronic stuff. :-)

[Flagman101]

Originally Posted by Privilege

I apologize if this an overly-basic question but did the iPad have GPS installed; ie; was it SIM compatible?

Mine isn't and so I only use it for practice. If close to land it works off the local towers and gives me a fairly accurate location. Once I get a mile or two out, it starts guessing my location.

It did not have a sim card.
I do think that it worked only with the internal gps chip and not WAAS or cell towers.

[Flagman101]

Originally Posted by JohnEasley

We used Navionics on an iPad on our boat successfully for a year. On one occasion, it did show us so far off course that it put us about 150 yards on land. After a quick reboot of the iPad, it was fine. From that point on, we rebooted it every day before departing and it was always spot on after that. Could have been your issue. Or maybe it was something else entirely.

I should have rebooted the I-pad yes. Did not think about that.

[Emerald Sea]

Originally Posted by Flagman101

In the end I'm not sure using an iPad and Navionics is a good alternative to a more expensive dedicated chart plotter.
I wonder if others have experienced similar problems.
Was it just this particular iPad?
One thing for sure, it was a good thing I was sailing familiar waters as I would have run aground if I did rely on the iPad for navigation.

What you are experiencing is not the fault of your iPad, its GPS or any other chart plotter for that matter. Marine charts cannot be written in stone! Most are produced from near ancient soundings when navigation and bathymetry tools were rudimentary. And perhaps the surveyor was sober!

Only where a survey vessel towing a bathymetry spread (depth sonar, GPS, etc) and corrected for tides will there be accurate charts and these can be found where there is commercial shipping or where a government has decided to make this expense. There is no incentives for the frugal yacht cruiser.

Most worldly locations, including those you have experienced in the Grenadines, have not been subject to such detailed surveys hence the data is, at best, speculative.

You have taken the correct approach - slowly with eyes and ears alert. Never let your guard down!

[Flagman101]

Originally Posted by Emerald Sea

What you are experiencing is not the fault of your iPad, its GPS or any other chart plotter for that matter. Marine charts cannot be written in stone! Most are produced from near ancient soundings when navigation and bathymetry tools were rudimentary. And perhaps the surveyor was sober!

Only where a survey vessel towing a bathymetry spread (depth sonar, GPS, etc) and corrected for tides will there be accurate charts and these can be found where there is commercial shipping or where a government has decided to make this expense. There is no incentives for the frugal yacht cruiser.

Most worldly locations, including those you have experienced in the Grenadines, have not been subject to such detailed surveys hence the data is, at best, speculative.

You have taken the correct approach - slowly with eyes and ears alert. Never let your guard down!

Thank for your reply.
But I do remember on previous charters using Garmin Chart plotter, being much more precise. I don't remember such high error margins.
Not sure what happened.

[Emerald Sea]

Originally Posted by Flagman101

Thank for your reply.
But I do remember on previous charters using Garmin Chart plotter, being much more precise. I don't remember such high error margins.
Not sure what happened.

Cartography institutions also pay for the exclusive rights to use a country's nautical charts. For instance, Garmin bought the rights to Indonesian waters a few years back (for areas where proper surveys have taken place). Navionics have done so in other locations. Some are shared. Many nonexistent but they still show contours on the charts (dangerous and liable IMO).

This is another factor to consider and another lesson: have more than one resource at hand.