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GPS - what do the techsperts say.

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Created by puppetonastring > 9 months ago, 13 Jul 2012
puppetonastring
WA, 3619 posts
13 Jul 2012 8:29PM
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Hi Poley friends.
I know theres a lot of you guys right into this technology.
Id really appreciate some feedback on whats the best Way-to-Go.
I'd like to get the best there is for a trip Im up for - crossing of the Torres Strait by kite power. .
Then have a unit to keep for general use once Im hooked (as Im sure I will be)
Also wanting to suss out the options for stocking it in the shop for others.

Really appreciate some feedback from those who know field to help choose whats worthy & what may not be.
All the stuff Ive seen on posts on SB would be of interest.
- obviously track logging - Im guessing they all do that but some may do it better?
- time & speed recording - as detailed as possible rather than just averages?
- anything new on the kiters hope for height of jumps would be awesome?
- compatibility with software for dragging out specific stats ?
etc etc.
All info appreciated including brands & sources.

Post or PM - all good
Taa in advance.

fanatic02
NSW, 304 posts
13 Jul 2012 10:36PM
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For a start !!!! you should probably go to the kiting forums where someone might be interested !!!!!!!!!!!!!

T 11
TAS, 811 posts
13 Jul 2012 10:44PM
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Hey Puppet I noticed on your site you say you are going to be the first single sailor craft to do the crossing but I think you will find Rick Burnup and his mates did this in the eighties on windsurfers and I can remember one of them broke a mast and they carved a new one from some bamboo off one of the islands on the way.
All the best for your trip should be a great adventure.
Most of us use GT31 gps they seem the best currently.

decrepit
WA, 12802 posts
13 Jul 2012 9:55PM
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yep, the GT31, saves very detailed data to an sd card, so you don't have to worry about loosing data if you can't download it regularly.
For speed accuracy the doppler data is included in the saved file.
I don't know about the best there is, I'm sure you could spend a lot more money and get something more accurate. But for it's cost, it's the best for speed windsurfing, may or may not be relevant to your needs.

Mark _australia
WA, 23526 posts
13 Jul 2012 10:00PM
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Considering you are kiting to another country, duty free could be the go.

puppetonastring
WA, 3619 posts
14 Jul 2012 12:02AM
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Thanks for positivity there T11. I'll check out the GT31 for sure.
If there is any background, sources etc on that 80's windsurf crossing I'd love to know about it.
I did hear a rumour from a random in the shop one day that 2 windsurfers took off from the Cape some years? ago totally unaided and were never heard of again?
Im guessing if it actually happened there would be official records somewhere. Havent found any yet though.

Richiefish
QLD, 5612 posts
14 Jul 2012 8:29AM
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do you want one for the purpose of navigation or just retrospective data (speed tracks etc) ?

elmo
WA, 8879 posts
14 Jul 2012 9:18AM
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G'day Puppet,

Sounds like an adventure

GT31 for data loging

For jumps and all the other twisting loopy spiny stuff the shadowbox is the go as it does the flat data logging as well as altitude and Gyro, it's what they are now using for jump contests

Look forward to reading about it (hopefully not a tale of woe)

grumplestiltskin
WA, 2331 posts
14 Jul 2012 10:47AM
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I would imagine that because you are planning an offshore adventure, you are wanting to check the gps to tell you where you are. The gt31 won't help with that coz it only logs data for analysis at a later time.
Surely you will need some sort of navigational gps like you would find on a yacht?

powersloshin
NSW, 1844 posts
14 Jul 2012 6:44PM
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grumplestiltskin said...

I would imagine that because you are planning an offshore adventure, you are wanting to check the gps to tell you where you are. The gt31 won't help with that coz it only logs data for analysis at a later time.
Surely you will need some sort of navigational gps like you would find on a yacht?


I am pretty sure that the GT31 can be used for navigation as well: you can set routes, waypoints and marks and navigate to them, but you cannot use maps, for that functionality I think you need to spend at least $500 for a Garmin

jn1
SA, 2683 posts
14 Jul 2012 7:18PM
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Hi Mate

The GT31 is good, and I've got one.. but I would regard it as old technology now. Also, I would regard the product as "fiddly" to use in the field (not a very good field device - buttons can be pressed, data erased/stopped, even when you lock it). Doubly so through the aqua-pack.

I think most modern phones have a GPS chip in them, so anything is possible (ie: "there is an app for that !" etc). A few guys at work like to use thumbdrive type "turn key" devices that fit into their pocket (due to the "accidently pressing something" scenerio). They slide a switch, lock the switch, and it runs.. and then just logs the data. This serves their application well..

.. but the GT31 is still an excellent device. It's got a bunch of other features (not related to Windsurfing) that I use all of the time. Infact, I use it more of other stuff than windsurfing.

Regarding the tracking feature of the GT31 mentioned above. It's very crude. The GT31 also requires a hard power reset after travelling 300km or more.

Whatever the case, make sure the device you purchase logs data in NMEA0183 format (and not solely a proprietary format). This format seems to be the defacto standard for GPS, tracking logging etc, and gives you access to a bunch of free or free to use analysis/visualisation software that is available on the Internet.

Good luck. Let us know what you get :)

J

kato
VIC, 3513 posts
14 Jul 2012 7:58PM
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puppetonastring said...

Thanks for positivity there T11. I'll check out the GT31 for sure.
If there is any background, sources etc on that 80's windsurf crossing I'd love to know about it.
I did hear a rumour from a random in the shop one day that 2 windsurfers took off from the Cape some years? ago totally unaided and were never heard of again?
Im guessing if it actually happened there would be official records somewhere. Havent found any yet though.


Another vote for the GT 31 ,especially if you wish to claim some record. The GT 31 has been tested and is rated as 99.98 correct if two are used. No other GPS has been passed, so use others at your own risk. More info at GPSSS or GPSKS.
I would use at least 3 for any attempts just in case one crashes.
Never had one fail once its set up right and not sure how you get it to delete files on its own perhaps opp error

jn1
SA, 2683 posts
14 Jul 2012 7:44PM
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Is that kinda like an "error located between keyboard and chair" type scenario Kato ? (or fat fingers error ?)


choco
SA, 4177 posts
14 Jul 2012 8:50PM
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don't get one of those that you use in a car.....it will keep telling you "where possible perform a U turn"

AUS02
TAS, 2039 posts
14 Jul 2012 9:21PM
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jn1 said...

The GT31 also requires a hard power reset after travelling 300km or more.


What do you mean?

decrepit
WA, 12802 posts
14 Jul 2012 8:22PM
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AUS02 said...

jn1 said...

The GT31 also requires a hard power reset after travelling 300km or more.


What do you mean?


Like wise?

I've used mine in Mandurah, driven to Sharkbay and the GT31 had no trouble. The old GT11 would come up with "travel long" when it couldn't get a fix. But the GT31 doesn't seem to have that problem.

jn1
SA, 2683 posts
14 Jul 2012 9:58PM
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AUS02 said...

What do you mean?




Given, it looks like there is a bit of "engrish.com" with the wording, but without knowing the proprietary code/circuits, I just go by what they are trying to say . Most likely, the unit needs to download the Almanac after a certain distance (used to make speed calculations), or it calculates the km per degrees constant only at start up ?. Who knows.

kato
VIC, 3513 posts
14 Jul 2012 10:41PM
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decrepit said...

AUS02 said...

jn1 said...

The GT31 also requires a hard power reset after travelling 300km or more.


What do you mean?


Like wise?

I've used mine in Mandurah, driven to Sharkbay and the GT31 had no trouble. The old GT11 would come up with "travel long" when it couldn't get a fix. But the GT31 doesn't seem to have that problem.


No probs with the Pit to L George either

FormulaNova
WA, 15090 posts
14 Jul 2012 9:36PM
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jn1 said...

AUS02 said...

What do you mean?


<snip>

Given, it looks like there is a bit of "engrish.com" with the wording, but without knowing the proprietary code/circuits, I just go by what they are trying to say . Most likely, the unit needs to download the Almanac after a certain distance (used to make speed calculations), or it calculates the km per degrees constant only at start up ?. Who knows.


Nah, that just means that if you move it a long distance, while turned off, that it needs to be reset. This is because it knows what satellites should be available in the area, but when you move it too far, it can no longer find them.

It then needs to listen to what is in the new location in order to get enough satellites to have an accurate fix. If it moves the same long distance while turned on, it should be able to progressively learn of the new satellites and have no problem.

decrepit
WA, 12802 posts
14 Jul 2012 10:16PM
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jn1 said...

>>>>

Given, it looks like there is a bit of "engrish.com" with the wording, but without knowing the proprietary code/circuits, I just go by what they are trying to say . Most likely, the unit needs to download the Almanac after a certain distance (used to make speed calculations), or it calculates the km per degrees constant only at start up ?. Who knows.


Agree with mineral, "cold start" is a process of finding where in the world it is, normally it assumes it's where it was last time it was on.
As far as the almanac is concerned, I don't think doppler needs it for speed calculations.

Also agree the GT31 is a bit fiddly to use in a waterproof container. But due to it's smart speed sailing mode, (speed genie) I don't need to touch it until I've finished for the day.

mathew
QLD, 2142 posts
17 Jul 2012 1:23AM
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decrepit said...
As far as the almanac is concerned, I don't think doppler needs it for speed calculations.


This is known as "ephemeris" -> FormulaNova is 100% correct.

Without accurate knowledge of the position of the satellites, your GPS wouldn't be able to determine doppler speed, as it wouldn't be able to take into account the relativistic effects of gravity.

ie: GPS clocks are accurate to an order of a few nanoseconds, where as gravity will affect the satellite clocks by the order of microseconds.

decrepit
WA, 12802 posts
17 Jul 2012 7:13PM
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Thanks Mathew, it's always more complicated than I think.



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"GPS - what do the techsperts say." started by puppetonastring