shawn
A Force-of-Nature *  
Member #: 403 Posts 255
Registered: 15-10-2003 Member Is Offline Mood: Chilled
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| posted on 4-1-2005 at 09:35 |
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GPS
I got a Garmin summit gps for xmas but ain't used it on the water yet - a few of my chums have used them at west kirby quite a bit -
people have racked up quite good speeds - my mate ken clocked up 32 kts on a starboard Evo! - windy John got 36 (i think) on an acid -
but so far this year the current record is 37kts........ on some kit I've never heard of.
I followed ken on a few of his 32kt runs (in the dark!) and believe me, it felt really fast, I thought my hair was going to burst into
flame!
Don't have a cow man!
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Wes
A Force-of-Nature * 
I Love Men in Uniforms!
Member #: 198 Posts 198
Registered: 27-4-2003 Location: Bath Member Is Offline Mood: Wanting SW winds!
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| posted on 4-1-2005 at 09:43 |
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If it was not for the fact that I have to buy a new large sail (went through mine last week) I'd buy a GPS as well. Seems like a
brilliant idea to me. I'd love to know how fast I actually sail, I bet its not hlf as quick as it feels.......
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shawn
A Force-of-Nature *
Member #: 403 Posts 255
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| posted on 4-1-2005 at 13:16 |
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yeah - I always thought I'd be doing about 30kts, but having been clocked at 32 (on broad reach, mirror flat water with slightly
overpowered 5.0), I realise that I usually sail a lot slower. 32 was scary - cant imagine 46!!!!!
Don't have a cow man!
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paul
A Force-of-Nature ** 
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| posted on 4-1-2005 at 13:50 |
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so just how acurate are these things these days ? I know the one on a friends yacht can be a little bit iffy, i.e. it thinks it's 500
yards inland while tied on a mooring, not to mention being 100ft below sea level at times which is worrying on a yacht 
Home Page
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Wes
A Force-of-Nature *
I Love Men in Uniforms!
Member #: 198 Posts 198
Registered: 27-4-2003 Location: Bath Member Is Offline Mood: Wanting SW winds!
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| posted on 4-1-2005 at 14:19 |
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I always fly with one, and often trust life and limb to it when calculating final glides and the like. Believe me, 100ft can make all
the differance between a marginal glide and a major crash. I have used one to get the dimensions of the gliding clubs club house and it
was accurate to within .5 m (it rounds to 1m) everytime.
I guess I'm trying to say I believe they are accurate.
However, I have no idea on the particular models.
I used to use another system (although the name escapes me) which used land based arials. It was accurate to within 500m, and couldn't
cope with speeds over 90knts. Terrible!
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justal
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| posted on 4-1-2005 at 14:24 |
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Appaently according to the blurb they are accurate to within 0.01 knots. The thing is although they may be slightly off as far as
absolute position goes... Good ones with WAAS (whatever that means) are supposed to give position accuracy to around 5m whereas
slightly lower spec ones say 15m... However, the system is owned by the US Military and they tend to introduce an error which can be as
much as 100m into the system. In some cases they can introduce even greater errors if they wish (I'm sure they have in Iraq)... The US
military obviously have units that correct for these errors....
However, for our purposes it doesn't actually matter how accurate the absolute positioning is as all we need to know is how far we move
in a given time so that we can deduce our speed. As far as this is concerned, the errors introduced my the US Military don't make any
difference, so they are pretty accurate.
Al.
URL: Pixelwave Design - Website Design Wales
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Personal Weblog: A Simple Life of Luxury in West Wales
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shawn
A Force-of-Nature *
Member #: 403 Posts 255
Registered: 15-10-2003 Member Is Offline Mood: Chilled
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| posted on 4-1-2005 at 16:11 |
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Mine usually sez it's accurate to about 20m. However, I've entered grid refs that have turned out to be several hundred meters out, but
I think that may be a mapping problem rather than accuracy (it's all abit complicated when u want to use it with a map).
I also managed to run at max speed 22.7 mph the other day, which I think would put Linford Christie to shame, so I'm a bit dubious
about that one too esp. considering all the mince pies n stuff weighing me down.
In short - I'm as yet undecided about exactly how accurate these are..... I think having it in a pocket confuses it too.
Don't have a cow man!
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paul
A Force-of-Nature **
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| posted on 4-1-2005 at 16:23 |
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doesn't it have to be strapped to the top of your head or something so it can see at least 3 satellites ?
Home Page
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shawn
A Force-of-Nature *
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| posted on 5-1-2005 at 12:53 |
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That would be ideal - and probably most accurate. However, purely on the grounds of extra wind resistance I'd probably not bother with
that option. The most common idea seems to be to put it in an aquapac and strap it to your arm/boom/mast. I don't think it would work
very well stuffed up your wetsuit sleeve.
Did u all read in boards mag this month that maestro Dunkerbeck himself is bringing out a range of windsurfing oriented GPS systems
which work on 7 satellites and should be spot on, and also have a range of other stuff including an emergency button u can press which
will send your co-ordinates to the mobile phone of your choice for easy rescue...... it's probably worth waiting for one of them to be
honest.
Don't have a cow man!
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justal
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| posted on 5-1-2005 at 16:30 |
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Except that they will no doubt be three times the price of a 'normal' GPS.
Sounds pretty interesting though.
Al.
URL: Pixelwave Design - Website Design Wales
Shop: Website Templates
Personal Weblog: A Simple Life of Luxury in West Wales
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Jonny
A Force-of-Nature ** 
Member #: 394 Posts 308
Registered: 6-10-2003 Location: North West Member Is Offline Mood: waitin for the next blow!
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| posted on 5-1-2005 at 20:10 |
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Hey Wes. Aviation law says your not meant to rely on GPS's for using them as an altimeter for determining your height to avoid
controlled airspace. However, I've often compared them in flight to my altimeter and the GPS is usually fairly accurate with my
altimeter although sometimes the GPS can be a few feet out which is nothing.
I use a Garmin GPS12 thats pretty old now but works well. Must be at least 6-7 years old and cost a fortune in its day. As its not
really worth much anymore. I spose I should purchase an aquapack and just see what speeds I can get windsurfing. One thing to note is
that my dads got an Emap and his GPS positional co-cordiantes are always a few metres out to mine. So it just gos to show that they are
not completely accurate for your positional location but as Al said, thats irrelevant for our use.
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justal
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| posted on 5-1-2005 at 20:19 |
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Shame the altimeter isn't more accurate though, it would be good if we could work out how high we were jumping as well as how fast we
are going!! 
Al.
URL: Pixelwave Design - Website Design Wales
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Personal Weblog: A Simple Life of Luxury in West Wales
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IainO
Pro
Member #: 153 Posts 93
Registered: 23-2-2003 Member Is Offline Mood: Closer to the sea now
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| posted on 5-1-2005 at 21:18 |
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quote:
Originally posted by Jonny
However, I've often compared them in flight to my altimeter and the GPS is usually fairly accurate with my altimeter although
sometimes the GPS can be a few feet out which is nothing.
Depends what type of altimeter you're using. Barometric are only calibrated to 20 feet and Radalts are accurate to 5 feet.
As Al mentioned the US Military can introduce deliberate errors which led to the maritime community introducing Differential GPS (DGPS)
some years ago. This was a receiver based at a known point that would measure the error introduced and send out the error information
to subscribers DGPS receivers giving accurate positioning.
Nowadays the errors are all but switched off and the inaccuracies are usually as a result of the number of satellites acquired and the
quality of the receiver/processor. Unless you've got an accurate clock signal (the GPS satellites use an extremely accurate atomic
clock) you've got errors straight away.
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Wes
A Force-of-Nature *
I Love Men in Uniforms!
Member #: 198 Posts 198
Registered: 27-4-2003 Location: Bath Member Is Offline Mood: Wanting SW winds!
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| posted on 6-1-2005 at 10:00 |
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Jonny, yep you are right, and I don't rely on it for telling me how high I am. I have a barametric (and arse for sub 100ft!) for that,
but to do final glide calculations, thats when I use it. Its linked to both an L-Nav and palmpilot using Winpilot for the moving map
display both of which give me an estimated arrival height while final gliding damn useful tools as well, definatly a handicap when they
go down!
However, despite having 2 GPS's, map, winpilot and years of experiance of where I can and can't fly, I still took a thermal over Hinton
parachute zone and shut it down for 1/2 hour! The public bollocking I got at briefing next day was more than justified......
Sorry - a little off topic there!
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justal
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| posted on 6-1-2005 at 16:42 |
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Got home from work and my GPS had arrived, so quickly read how to switch it on and reset the Max Speed and then headed off to the
beach. I checked the current speed reading on the GPS against my vans speedometer and it seemed spot on. I was pretty amazed at how
little movement you need to make before it picks up on it.
The wind was around 25 knots and the sea pretty rough so I rigged my 5m sail and big board, reset the max speed on the GPS and got out
there. The conditions were just perfect, I was well powered up and flying off the waves, with some massive jumps at times. The sea was
pretty lumpy even right out the back where there were some monster waves. Just perfect.... Not great for full-on speed with my GPS, but
still an amazing session.
Got back to the beach to check my Max speed and realised I didn't actually know how to do that, so after derigging had to drive all the
way home at less than 15mph to make sure I didn't exceed the speed I had done on the water.
I've since read the instructions and found out that my max speed was 28.7mph... Not great, but in 4 foot lumpy seas not too bad either
I don't think.
Al.
URL: Pixelwave Design - Website Design Wales
Shop: Website Templates
Personal Weblog: A Simple Life of Luxury in West Wales
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Wes
A Force-of-Nature *
I Love Men in Uniforms!
Member #: 198 Posts 198
Registered: 27-4-2003 Location: Bath Member Is Offline Mood: Wanting SW winds!
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| posted on 7-1-2005 at 08:39 |
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Time to pout, stamp my feet and start shouting
want one! want one! want one!
Damn I need more money!
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Bananaman
Pro 
Member #: 522 Posts 99
Registered: 26-1-2004 Member Is Offline Mood: Re-invigorated
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| posted on 7-1-2005 at 10:26 |
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Justal, what is the make and model of the GPS you got? Also where did you carry on whilst windsurfing? also how much was it and where
did you buy it from?
Sounds like a fun thing to have which could make the whole experience even more interesting.
[Edited on 7-1-2005 by Bananaman]
A New Breed Of Superhero
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justal
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| posted on 7-1-2005 at 13:40 |
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Its a Garmin Etrex which I got from thenavigationcompany.com for £84.95
I put it inside an aquapac which I got from eBay for £1.99 and then put the aquapac around my neck and stuffed the whole thing
inside my wetsuit.
About to got out and play with it again in a mo!!
Al.
URL: Pixelwave Design - Website Design Wales
Shop: Website Templates
Personal Weblog: A Simple Life of Luxury in West Wales
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paul
A Force-of-Nature **
Member #: 5 Posts 445
Registered: 24-7-2002 Member Is Offline Mood: Well Chuffed
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| posted on 7-1-2005 at 14:00 |
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silly question I know, but how does it work if it's inside your wetsuit ? don't these things need to be able to confirm their position
with a satellite.
Home Page
http://www.nationalwindsurfingweek.org
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justal
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| posted on 7-1-2005 at 15:57 |
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I guess so, but it doesn't have 'eyes' so isn't doing it visually!! I don't know what it does use, but it seems to work from within my
wetsuit. It works inside my van as well, but doesn't work inside the house, although it does sometimes just pick up a signal from
within the house.
I guess the weather conditions will make a difference as well, but it doesn't get much worse than it was today weather wise and it
worked OK.
Al.
URL: Pixelwave Design - Website Design Wales
Shop: Website Templates
Personal Weblog: A Simple Life of Luxury in West Wales
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Pixelwave Web Design.
justal@forces-of-nature.co.uk