View Full Version : Which GPS ???

14th October 2009, 01:38 AM
Recently lost my Gecko 301 (dont ask !!!).Its been great ;very reliable; no water ingress and its taken a few knocks.Was going to simply get another but noticed on GPS speedsurfing thats its not used that much. Whats best make/ model for reliability and ease of use now ??? And where from for price ??

mark h
14th October 2009, 02:17 AM
GT31 is best, shows more info prior to down loading. If your using GPSSS, both the Gt31/GT11 and the older Garmins are excepted. Im still using my old Garmin forerunner 201, but will upgrade very soon to the GT31. The GT31 is proving to be just as reliable as the Garmin and equally as easy to use (just different). If your in the UK try these suppliers:




Both have excellent reputation and both use GPSSS.com

14th October 2009, 07:44 AM
Hi Floyd, i agree with Mark, GT-31 is "the one" for speed sailing and the only one fully accepted in GPS Speed Surfing championships, it has the last generation chip Sirf III and is the only one that you can insert a 2Gb memory card and save months of sailing data and use it own memory as a back up. You can take a look at the manual at http://www.freight-focus.com/download/gt31_manual.pdf

14th October 2009, 05:28 PM
Thanks to pair of you for replies.Will get one ASAP.
Good sailing

14th October 2009, 08:55 PM
GT-31 stores Doppler speed measurements in to track. Doppler speed measurement is much more accurate than position based speed measurement. Garmin GPS devices are also capable of Doppler speed measurements, but they donít store them in to track. They store position and time and from this they calculate speed. Max speed reading shown on Garmin GPS is derived from Doppler speed measurement and is more accurate than max speed reading from Garmin GPS track.
Iím convinced Garmin hardware is capable of recording Doppler speed measurements in to track, only thing they would have to change is software, but they donít want to do this.
You can insert 2Gb or bigger memory card in Garmin eTrex Vista Hcx and many others, GT-31 is not only one with this capability.

14th October 2009, 10:00 PM
Hi Unregistered.
Yes you are right. I think even my old Garmin 12 (from circa 1997) used doppler for speed read out,but did not store speed info. All its future speed measurements were dS/dT and hence reliant on positional date . (Including trak logs)

There` a number of ways you can see this to be case but main evidence is from Garmin`s accuracy data .Even on older units accuracy claimed for speed read out (on unit) was way better than that claimed for position. (and constant) If speed was dependant on position its accuracy would not be constant and at best could only match positional accuracy. (ie bigger distances would give more accurate speed figures; which they dont.) (Its an old argument and has been aired on here a few times)

Vbox have been building a speed measurement unit for use in F1 (and others) for years. One model totally relies on doppler from GPS time signals.(Particular unit gives no popsitional data though)

Its only been a matter of time for GPS builders to start recording the doppler speed data. (One chap at Garmin told me units could not operate without knowing speed before positional data was calculated ???)(ie its the first thing unit does???!!)

Just ordered Genie/Aquapak/card

21st October 2009, 10:29 PM
Just taken delivery !! Seems great but a bit more complex than Gecko .
Cant see difference between ordinary "Speed" setting and "Genie" setting and cant set time to GMT +1 . (neither really matter and I`ll figure it out some time)

Not had any records yet and was wondering if GPSR (replay) will still be compatible ???

And what interval is for GPS speedsurfing.com. ???

(Got 2Gb card; does it have to be cleared via PC ??? (when it eventually gets filled?)

Good sailing

22nd October 2009, 07:58 AM
Hi Floyd, congrats, once you get dialed with GT-31 its easy as 1-2-3.
"Speed Genie" is a program developed by Dr. Tom Chalko specially for "us" windsurfers, it automatically displays current speed while you sail and when you stop depending your configuration it shows immediately: Max Speed, 2 Seconds Max AVG, Max 2 sconds Max speed and you can ad History, Min, etc.
I would recomend you to have a look at http://mountbest.net/setting-up-navi-GT31.htm this is the best web site for tunning up your GT-31 for windsurfing, follow carefully their steps and your done, I downloaded the new GT31_FW_V1.3B1014a firmware with it new large fonts for "Speed" and "Genie" and now is really easy to read speeds while sailing.
If you are more into full GPS usege take a look at http://www.splitbrain.org/blog/2008-12/07-locosys_genie_gt-31_gps_review
Just my two cents.

PS. Remember to use it inside an "Aquapack"

23rd October 2009, 09:42 AM
Hi again Floyd, yes GPSR is compatible and you can also test Real Speed at http://www.intellimass.com/RealSpeed/Index.htm
My 2GB is not full yet in one year use, I think it is possible to erase data through comp but no fully sure, the best wat is to format the card with the GT-31 in "Memory Card" > "Format Card" but you have to stop log first at "Memory Card" > "Log Switch" > "Of" > Restart unit and then format your card, remember to check again "Log Switch" > "ON-FIX" > restart unit, to start log again.

23rd October 2009, 07:48 PM
Thanks Will.
Both posts helped.
Reformatting does erase Card.
Getting unit sorted. Been on a few test runs (in car) and it worked fine. (Transfer to PC etc) (Using GPSR V6 via Card port in PC)

Gecko was very different in usage.

Trying to run in GPSAR (Action Replay); but not had much luck yet. (Will get there !!)

Thanks again

7th November 2009, 07:47 PM
The original (Free) GPSAR v3.3 does not read the newer .sbp and .sbn file formats from the GT-31. To use it you will have to convert your files to .gpx and may lose some data accuracy.

GPSAR-Pro is adapted for the new (more compact and contain more accurate data) file formats.

RealSpeed and GPS-Results and GPSAR-Pro are the preferred software packages for use with the GT-11 and GT-31 and for GPS-Speedsurfing.

16th November 2009, 10:03 PM
just bought a northstar 550 gps for upstairs but am a bit confused about which card to get
can someone tell me the differance between NT , NT & Max, I have a NT downstairs in the raymarine but dont want to be pulling it out whenever the need arises

17th November 2009, 08:08 PM
Must be a big board you`ve got !!!