do yu have to use a gt31 or what other brands are there as I see alot of units on ebay?
Do yourself a favour and get a GT31. 95% of people will agree but there are always a few out there that are going to tell you otherwise.
A search of "garmin" will no doubt bring up plenty of threads.
GT31 or nothing
if you are running and biking then garmin
for windsurfing I don't recomend garmin to anyone
I am not making any claims about which product is better, but I am just curious why Garmin is frowned upon????
I have a Garmin Geko, and have had it for many years from when it was first released. Initially used it for bike riding and walking and recently windsurfing. The only problem I have ever had was at the beginning of 2010 when it had a firmware bug that caused dates to scramble. This was simply fixed with a firmware update. Other than that it has been totally trouble free and gives consistent results. It takes about 5-15 minutes to upload tracks.
Most people I know with GTxx have had issues that have caused them to miss sessions. They are also larger and less waterproof. Memory size on Garmin may become a problem if going for really long sessions.
I am not saying that Garmin's are superior... I am just curious why people are so down on them??
I also had the GG it's not a bad unit as it does all the things you need it to do, it's just there are better and cheaper GPS's out there now.
The GG works in trackpoints whereas the GT11's and 31's use doppler which has greater accuracy.
I think the garmin display is doppler, but it doesn't store this data, only trackpoints.
Not sure about garmin models, but some of them only recorded data at 2sec intervals, instead of the GT's 1 sec.
That might not sound like a lot of difference, but I've been very surprised how much WS speed changes in very short times.
The Gpsss site was talking about discounting garmin figures by a few knots to allow for their lack of accuracy.
It is actually because for speed sailing the GT-31 is much better!
It records more accurate 'Doppler ' derived data as well as the data we need to verify that accuracy.
It really is the only unit suitable for speed sailing. There are a few other Loggers or dongles that can produce the same or similar data but none are as convenient as the GT-31 or have a screen display. Certainly none of them have the incredibly useful 'Genie' display functions.
The Locosys GPSes are good for windsurfing as they are easy to use and are accurate however they suffer from an incredible design flaw for a electronic device used in a marine environment. They are not particularly waterproof.
The GTs would be fantastic if they had a waterproof case similar to the cases that come with GoPro cameras.
There many opinions on the accuracy of the Garmin units, but the fact is that the garmin units are accepted by GPSTC which is where most of us are posting results, and for that reason alone, these arguments do not hold much weight (until the rules change!!). It seems that people using GTxx just like to think garmins read higher to make them feel better. I have never seen any evidence that my results are inaccurate. I find that the max speed results I get on the display (doppler) are within fractions of a knot of what is loaded into the KA72 site (track point). And for anything over longer period than 2s, any error would be averaged out over multiple samples, so really it is only 2s that would be out by anything measurable... and my difference between 5X10 and 2S is similar to what others get at my sailing location.
I use 2s sample interval.... since the max speed is over a 2s interval, the results should be accurate as 10s is a multiple of 2s, so 5X10 is covered. If the minimum time slot used for results is 2s, there is little benefit in going quicker than that... at 2s no software interpolation takes place. If anything, a 2s interval would reduce the max possible speed.
I get that the GTxx is the bees knees, and better suited in terms of technical spec and accuracy, but my garmin geko does everything required with what appears to be good accuracy, and it seems to be alot more reliable than the GTxx when doing it. So I understand you guys recommending your GTxx, but do you really need to put the other options down for no real reason. For me I want a unit that is accepted, gives consistent results, and does so reliably without losing data. Garmin does this better than most.
Cheers,
Adrian
Adrian,
I think you'll find the reason for allowing Garmins in the challenge noted by Nebs in this link www.seabreeze.com.au/forums/Windsurfing/Gps/GTC-Doppler-for-all-alphas-in-2010/?whichpage=2&index=33
I think once you're punching speeds above 40knots (something I won't have to worry about anytime too soon) it would probably be considered poor form if you persisted with a Garmin in lieu of a Navi. That same thread above, Sailquik noted that the challenge should exclude the use of Garmins.
If Adrian gets speeds up in the 40 knots area I'll loan him my GT-11 and buy myself a new GT-31. My GT-11 still works but in a particular way. It cannot save data to the card while on the go. It just creates a bunch of little files.
However once back home I can save the data log data onto the card and then upload it. Its a bit of a work around but it works and I'll keep doing it till the GPS completely dies.
Hey Adrian,
If the garmin floats your boat then go for it, we're not going to stop you. In fact we're happy that you're taking part!
As others have said, if you just want a record of where you went on the day and a rough indication of speed then the garmin units are fine.
However the GT-11/GT-31 units are a lot more accurate, and because they provide both trackpoints and doppler data it makes verifying tracks a whole lot easier.
As the administrator I have to verify the odd track, and I can tell you that if everyone was using Navi's then it would make my job a whole lot easier. In the end it comes down to what value you place on your own records -- do you want to have that nagging doubt in the back of your mind when you say you hit 40.01 knots? Do you want people to say "Yeah but come on, we all know your unit records a little bit higher than everyone else's so that result is a bit suss". Or do you want to say with absolute confidence that you did it? Of course if you're not interested in hitting 40 (like me 
) then this isn't an issue.
Your call.
I am with you Adrian.
I am nowhere near 40 knots now, but maybe one day!!?? but doubtful. I would be replacing all my equipment let alone the GPS to get there.
I am not sure statistically what the general sailing style and resources of most people on the GPSTC are. Clearly if money is no object and you want to go 40+ or bust, then you get all the right equipment to do it, and this includes the most accurate GPS (and replace it when it fails). For me I am sailing a FSW board with non cammed freewave sails, which are mostly atleast 4 years old. I had a Garmin from around 10 years ago, so I use it. I had planned to change to GTxx if it failed, but the Garmin is just so bulletproof that I think it will never break... but I certainly see plenty of GTxx with issues... I know of several people with missed sessions.
Again I don't know for sure, but I believe there are more people out there enjoying GPS sailing on less than perfect windsurfing equipment that are just doing it for the fun of it probably well south of 35knots like me. For them they just want equipment that just works as it is intended with good reliability, and minimal fuss to use it and post data. I think the Garmin makes a pretty good case for this.
If I make greater than 38knots ever... I will get a GTxx for sure in hope of the big 40.
I'm wondering when the locosys people are going to fix the one MAJOR design flaw in the GT's. ie having the toggle stick protruding out from the face of the unit. Surely they must know that the units are used in bags that will be pressing on the stick ?
Stick it on speed genie and put it in one of these and never have a problem. Ever. 
Garmin,s still need a bag and run out of track points and battery power
