Page 2 of 4 FirstFirst 1 2 3 4 LastLast
Results 8 to 14 of 23
  1. #8
    Senior Member
    Join Date
    Nov 2009
    Posts
    3,876
    It is specified as waterproof to IPX7 which I think most involved in watersports know is not sufficient. It is generally used as a standard inferring "showerproof". All the advice from those that provided the set up details for windsurfing, advised using an aquapac and most retailers offered a bundle including the aquapac. So yes, it was obvious that GT-31 was not sufficiently waterproof without being used in conjunction with an aquapac. One look at the bottom trap door that gives access to the SD card and charging port also tells you immediately it is not sufficiently sealed for immersion...there are no seals on that trap door!!
    Spending 2 minutes to shape a piece of neoprene or deckpad to hold the face of the aquapac off the buttons is hardly a major chore either.

    GPS Speedsurfing specified the degree of accuracy it required. That included the use of dopler, a minimum of 1 per second readings, and the number of satellites it could simultaneously track. For a long time the GT-31 was one of only a few that met those standards...............no under table handshakes! I'm not sure even now whether the new Locosys model has yet been accepted for Speed events despite the fact it records 10 per second readings etc.

  2. #9
    Senior Member
    Join Date
    Jan 2008
    Posts
    1,363
    IPX7 ( claimed standard for GT31) is no ingress of water at a depth of 3ft ( its an American standard) for 30 mins..

    My Garmin 12 is over 20 years old, better built, same waterproof rating, bigger screen , has more navigation features and critically still working. Folk have crossed Atlantic on hand held GPS, I wouldn't attempt to cross room with GT 31...If it were red, pink or yellow it would look fine for grandsons toy box....but wouldn't last long in there. Basically, on any objective measure of durability...its sh!te....

    Yes, it has good speed features but by no means unique or that cheap, only reason it was popular was because of endorsements from speedsurfing.com. Reckon Garmin were building then for pence...
    Last edited by Alphie; 30th April 2018 at 11:54 AM.

  3. #10
    Senior Member
    Join Date
    Dec 2007
    Posts
    2,376
    The new Locosys GW-60 is the one used on GPS-Speedsurfing as the GT-31 isnt available new.
    Weymouth Speedweek still use the GT-31. From what I remember about FB posts, I think the problem with the GW-60 is battery life, it only lasts 5-6 hours, whereas the GT-31 will last all day.
    Luderitz uses sync'd video cameras.

    I used to have a Garmin Foretrex 210 and remember people comparing the speeds to a GT-31 and they were within 0.1%. I've found a post, #110 on here:
    http://surf-forum.com/forum/thread/1...t-31/?pageNo=6

    It makes sense to compare only the fastest 10sec run in my opinion.
    Foretrex 82.776km / h
    GT 82.595km / h
    This deviation is also exactly in the known frame.
    The size differences are known to exist in the pure Maxspeeds. The Foretrex shows a bit higher 10sec Speeds, but that's not the deviation.

    I currently have a secondhand Garmin Forerunner 310XT watch and someone has compared the speeds to a GT-31

    https://www.gps-speedsurfing.com/def...val=26328.html

    Isit OK to use a Garmin Forerunner 310XT? I tested against a GT31 in mycar and found it to be within 0.1 to 0.3% of the GT-31.

    Ihad a session and used 310XT and GT-31. Dislay max speeds were veryclose as were 10sec etc calculated by software. There was a 0.3knotdifference in 1 sec max speed. Is that good enough to use 310XTreliably?


    The Foretrex 201 battery gave up, I had it 2009-2016 and maybe 180 sessions. The secondhand one I've used 190 times and its still going. Sometimes I have to scratch the contact points on it to get a connection for recharging.

    There are a few grumbles on the Seabreeze forum about GW-60 straps breaking, but someone mentioned if the watch is chucked in a kit bag the strap may be bent back and breaking/weakening it. I always attach mine to the handle on the bucket I use for putting my wet kit in so I dont forget to take it.
    Last edited by phil_in_poole; 30th April 2018 at 12:25 PM.

  4. #11
    Senior Member
    Join Date
    Jan 2008
    Posts
    1,363
    Good info Phil.
    The GW 60 is listed as being fully waterproof...to a depth of 50m...Think I,ll get one of those.
    Feeling underdressed sailing without GPS...

  5. #12
    Senior Member
    Join Date
    Nov 2009
    Posts
    3,876
    Alphie......yes IPX7 is immersion in 3 ft of water for 30 mins...BUT that says virtually nothing about temperature variation out of water, then into cold water; or water pressure. In the IPX7 test neither the device being tested nor the water is moving. Both are still. Jump off a board into the water and the pressure exerted on any seals if far greater than just standing under 3 ft of ( still) water. I have used my GT-31 for hiking in the rain without the protection of an aquapac and that presents no problems.

  6. #13
    Senior Member
    Join Date
    Jan 2008
    Posts
    1,363
    " One look at the bottom trap door that gives access to the SD card and charging port also tells you immediately it is not sufficiently sealed for immersion...there are no seals on that trap door!!"
    Exactly...
    In 3ft of water for 30 mins sounds like immersion to me ????

  7. #14
    Senior Member
    Join Date
    Dec 2007
    Posts
    2,376
    Doppler vs non doppler.

    I remembered I had a GW-60 device track from looking at a friend's issue with his alphas.
    In GPS-Results you can uncheck the doppler tick box and use the positional data in the track instead.
    There is about 0.25% difference overall. Thats enough of a difference for the top records, but not much of a difference for us normal sailors to worry about.

    2 second maximum speed and average of top 5, 10s speeds and average of top 5 etc.

    Click image for larger version. 

Name:	doppler compare.jpg 
Views:	47 
Size:	30.8 KB 
ID:	16154

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •