What is your backup GPS solution?

Discussion in 'Ask All Sailors' started by Jackdaw, Dec 6, 2018. Add this thread to a FAQ

  1. Allan12210

    Allan12210

    Joined Jan 22, 2008
    1,436 posts, 173 likes
    Hunter 34
    US Alameda CA
    For back up I always have my GPS to double check my charts plus compass (and sometimes depth sounder). I'm such a contrarian.
     


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  2. sesmith

    sesmith

    Joined Jul 1, 2010
    654 posts, 133 likes
    Seaward 25, Catalina 350
    US Ithaca, NY
    Nothing is 100%. But if your main unit has a 5% chance of failure and your backup has a 50% chance of failure, then you've increased your chances of success from 95% with your main unit to 97.5% with a half-a$$ed backup aboard. :)
     


  3. Gunni

    Gunni

    Joined Mar 16, 2010
    5,943 posts, 1,488 likes
    Beneteau 411 Oceanis
    US Annapolis
    I have only had the civilian GPS sat network go down on me one time. It was up near Baltimore during the the Kuwait war (1990). My handheld Garmin 88 lost it’s signal. A crew member simultaneously pointed to the sky where the new B-1 bomber was coming overhead, returning from the ME. Signal came back up moments later as the plane cleared the area. I assume it was related jamming.

    The early GPS devices could establish a pretty accurate location fix with just 4 or so satellites, I assume that even if some malign actor took down a few of our now very large sat array you could still get a fix that was more accurate than dead reckoning or even a sextant. Fixes would be slow, but the technology seems pretty flexible. Especially under a full-dome horizon (at sea).
     


  4. TomY

    TomY Alden Forum Moderator

    Joined Jun 22, 2004
    1,705 posts, 1,635 likes
    Alden 38' Challenger yawl
    US Rockport Harbor
    Our redundancy of GPS devices has grown quickly. These days we have at least 4 separate GPS receivers onboard just around home. If we're off for a few weeks in NE, we'll have at least 6 or 8 depending upon who's with us(you can have guests download a free nav program for their own fun).

    The ship mounted CP used to be the primary but now it's hard to say which is the back up, today. I like an Ipad for my main navigation, piloting and route planning but phones are becoming more useful for navigation.

    I like separate software for it's unique functions and settings and even opinions. I can set different reference bearings on screens that help me pilot.

    Portability of these devices is important to me because weather and sailing conditions determine where I'm piloting from in cockpit or down below. For that reason I've installed a few USB charger points and in fact putting in at least one more.

    Today is like having a whole team of navigators below at a huge chart table doing the hard work of keeping track of your boat while you concentrate of keeping a lookout.

    Nav station.jpg
     


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  5. sailnoproblem

    sailnoproblem

    Joined Oct 10, 2011
    502 posts, 152 likes
    Tartan 34C
    US Toms River, New Jersey
    I see your first mate has a watchful eye on GPS! My God what did sailors do before GPS, chart plotters, etc.?
    When I was into sport fishing I always wanted to arrange a fishing tournament without the use of any electronic equipment. I was never able to but what a hoot it would have been. I bet the old salts would have loved it.
     


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  6. dlochner

    dlochner

    Joined Jan 11, 2014
    3,617 posts, 1,672 likes
    Sabre 362
    113 US Fair Haven, NY
    Sticking with just electronic nav aides only, the answer is in combinational probability.

    The chance of any one device is not working is 50%, either it works or doesn't. The chance of 2 devices not working is ½ * ½ or there is a one in four chance of not having any device working. With 3 devices, the chance of only having one device working is ½ * ½* * ½ or ⅛. And the odds continue to get better.
     


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  7. dlochner

    dlochner

    Joined Jan 11, 2014
    3,617 posts, 1,672 likes
    Sabre 362
    113 US Fair Haven, NY
    Yes I do. The gps chip is on the cell phone chip. Cellphone service is not needed, just the cell phone chip.
     


  8. TomY

    TomY Alden Forum Moderator

    Joined Jun 22, 2004
    1,705 posts, 1,635 likes
    Alden 38' Challenger yawl
    US Rockport Harbor
    I know what I did: I sailed less.

    When the captain is also the navigator, sailing along a coast with a chart in the cockpit (or below in weather), piloting my location with pencil and rules, taking bearings, was at times, a lot of work.
     


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  9. TomY

    TomY Alden Forum Moderator

    Joined Jun 22, 2004
    1,705 posts, 1,635 likes
    Alden 38' Challenger yawl
    US Rockport Harbor
    Our Ipad 2 doesn't, so we have a separate GPS receiver (Garmin Glo).

    The next tablet will be GPS enabled. Trouble is, Apple stuff seems (to me) to last forever. This one runs about 8 or more hours a day at home and has since we bought it maybe 8-9 years ago. It hits the floor at least once a day...
     


  10. dlochner

    dlochner

    Joined Jan 11, 2014
    3,617 posts, 1,672 likes
    Sabre 362
    113 US Fair Haven, NY
    They don't break, but they do get to a point where they won't run the current OS and newer programs won't run on them. And they get slow.....
     


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  11. TomY

    TomY Alden Forum Moderator

    Joined Jun 22, 2004
    1,705 posts, 1,635 likes
    Alden 38' Challenger yawl
    US Rockport Harbor
    That is true. This one is used for music, movies, internet. It still has the Garmin Blue Chart app installed when nearly new and that works fine. It may finally end up on the boat squirreled away in the chart drawer, the ultimate - drop dead - last gasp,... backup.
     


  12. nat55

    nat55

    Joined Feb 11, 2017
    171 posts, 164 likes
    Gulfstar 1979 Gulfstar 37
    Un BELFAST
    I've got this crew below decks.....oh and a sextant, though I only use it offshore....
    [​IMG]
     


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  13. Parsons

    Parsons

    Joined Jul 12, 2011
    744 posts, 316 likes
    Catalina 36
    US Bay City, MI
    I don't have this problem because I only sail on a lake. I'm never more than a few dozen miles away from rocks in any direction, and I kinda know which direction to go. If my GPS(s) fail, and I'm not within soundings, I'll just head over there until I can figure it out from paper charts. Most of the lake-shore is soft, anyhow.

    As the old folks say around here, you're never more than 700 feet from land when you're on the lake. Of course, that may be straight down. :biggrin:
     


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  14. Crazy Dave Condon

    Crazy Dave Condon

    Joined Jun 8, 2004
    7,258 posts, 786 likes
    -na -NA
    US Anywhere USA
    Before the day of cell phone, GPS and all the modern gadgetry, I use to carry a simple radio with A M stations. In an area at night this helped. A young sailor left the radio turned down draining the battery and on top of that lost the charts overboard. I took out my VAstate highways road map to include the Chesapeake Bay triangling two radio A M stations. Got me in safely
     


  15. rgranger

    rgranger

    Joined Jan 19, 2010
    6,123 posts, 1,604 likes
    Hunter 26
    US Smith Mountain Lake
    I like that. In the NC outerbanks (sound side) I could claim to always be within 20 feet of land. I doubt that will make the admiral happy but my kids do like bad dad-jokes.
     


  16. ifmdalvey

    ifmdalvey

    Joined Feb 2, 2010
    312 posts, 22 likes
    Island Packet 37 Hull #2
    US Harpswell Me
    Jackdaw, when was the last time you had a GPS failure? i am not talking of individual units but the space borne system. I am going to guess never. Apart from localized military exercises where low power jamming might be practiced but will be NOTAM`d. The DOD have a responsibility for the system and its integrity, which is why every aircraft flying is dependent upon GPS. In the old days when i was in the military, we used to gun up the GPS sets with secret codes that would make it immune from deliberate spoofing and provide a better positional accuracy, that stopped a very long time ago.
    An extra receiver, compass, charts and the knowledge of how to use them is all you need.
     


  17. JRT

    JRT

    Joined Feb 14, 2017
    1,174 posts, 390 likes
    Catalina 310
    211 US Lake Guntersville, AL
    My left eye is a backup to my dominate right eye for my navigation on the lake...
     


  18. Simon Sexton

    Simon Sexton

    Joined Nov 1, 2017
    547 posts, 250 likes
    Catalina 25 Tall Rig
    Valiant US Watergate Marina, Kemah, TX
    Charts and mathematics.
     


  19. Simon Sexton

    Simon Sexton

    Joined Nov 1, 2017
    547 posts, 250 likes
    Catalina 25 Tall Rig
    Valiant US Watergate Marina, Kemah, TX
    I couldn't agree more.
     


  20. Johann

    Johann

    Joined Jun 3, 2004
    231 posts, 38 likes
    Hunter 336
    US Pensacola
    This was my VFR backup in the T-37...

    upload_2018-12-7_13-19-55.png

    I guess it would work just as well on the water :biggrin:
     




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