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Skiing with an etrex vista


Guest Joe BW

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Guest Joe BW

Just bought a Vista today and very pleased with it so far. Obviously I haven't had time to try out everything yet, but it seems to work as I had expected.

 

Sorry if this has been answered before, but I couldn't find much info about skiers using a GPS when I searched the forums. Do any of you out there take a GPS with you when skiing and if so, what is the most practical way to be able to find out how far you've been in a day, how fast you've been etc? I think it would be impractical to take it out of a pocket, turn it on, get a lock, turn it off, put back in pocket etc at the end of every run (with ski gloves on)!

 

Will a Vista work in a ski jacket pocket, or do you need to keep it more out in the open? Any tips would be much appreciated (even stating the obvious) as I'm a newbie to all this.

 

Thanks

 

[This message has been edited by Joe BW (edited 05 January 2002).]

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Guest DaveGeo

I am going to do the same thing. I want to leave the GPS on all day to provide accurate info.

 

Have thought about strapping the GPS to my jacket which seems a bit awkward, using some type of ski pass holder, or seing if it will work through an outside jacket pocket (prefered, but don`t know if it will work)

 

If all else fails I think I will strap it to a ski pole, I am going begining of Feb and begining of March and will let you all know how I get on.

 

Does anyone know how accurate the GPS will be over this type of terrain assuming it has to compute altitude very accurately to provide distance and speed?

 

Dave

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Guest jeremyp

quote:
Originally posted by DaveGeo:

Have thought about strapping the GPS to my jacket which seems a bit awkward, using some type of ski pass holder, or seing if it will work through an outside jacket pocket (prefered, but don`t know if it will work)

 

If all else fails I think I will strap it to a ski pole, I am going begining of Feb and begining of March and will let you all know how I get on.

 

Does anyone know how accurate the GPS will be over this type of terrain assuming it has to compute altitude very accurately to provide distance and speed?

 

Dave


I'm going to do somethingsimilar on my holiday starting 19th Jan. I'm pretty sure my GPS will work in a pocket or in my "bum bag". I would definitely not recommend attaching it to a pole because the chance of losing it would be pretty high.

 

As regards speed calculation, I assume my GPS calculates horizontal displacement i.e.doesn't take into account the fact that you might be going down a 30 degree slope (actually 30 degrees is very steep for a ski run). My GPS has a pressure altimeter built in so I should be abl to get accurate height readings.

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Guest Cape Cod Cache

WOO HOO!!!!!

Yup, I ski with GPS, New England areas of Loon, Attitash, Cannon, Waterville Valley, Cannon, Sunday River, and some others... I keep my Garmin 48 in my pocket, good reception. I have a pix I should scan; me ontop of Loon with my GPS.

Loon Mt: N44d02'15.5"/ W072d37'39.9"

 

This could be an interesting thread.

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Guest DaveGeo

displacement i.e.doesn't take into account the fact that you might be going down a 30 degree slope (actually 30 degrees is very steep for a ski run). B]

 

I hope and think you are wrong. I use the gps in the car and it is spot on with the odometer which does allow for change in altitude. In addition to this the gps does plot altitude and it would seem daft not to take this int account.

 

Does anyone know the answer for sure?

 

Dave

 

P.S. 30 degrees steep? Steepest I have skied is 62 degrees - that was steep!!

 

Let us know how you get on with it on your hols.

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Guest Joe BW

Thanks for your replies so far - I am off skiing in about 2 weeks so will be able to try out various places to locate the Vista and see what happens!

 

With regard to car speedometers, I have tested my GPS against the speedometer in two cars so far (on the flat), and in both cases the car's speedometer has shown significantly faster than the GPS. At 20mph, the car showed 25mph and at 60mph, the car showed 67 mph. This is in the UK. Now, what's interesting is that whenever I've been on holiday in the USA and rented a car, I always thought the speedometers seemed to be much slower - always put it down to bigger cars, wider roads. BUT perhaps, American cars have spot-on accurate speedometers and British cars don't. Any views/research on this? Just curious.

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Guest DaveGeo

quote:
Originally posted by Joe BW:

Thanks for your replies so far - I am off skiing in about 2 weeks so will be able to try out various places to locate the Vista and see what happens!

 

With regard to car speedometers, I have tested my GPS against the speedometer in two cars so far (on the flat), and in both cases the car's speedometer has shown significantly faster than the GPS. At 20mph, the car showed 25mph and at 60mph, the car showed 67 mph. This is in the UK. Now, what's interesting is that whenever I've been on holiday in the USA and rented a car, I always thought the speedometers seemed to be much slower - always put it down to bigger cars, wider roads. BUT perhaps, American cars have spot-on accurate speedometers and British cars don't. Any views/research on this? Just curious.


 

On my car (Vectra)the speedo shows about 1.5mph faster than the gps at most speeds, however the odometer is very precise. I assume the speedo is faster to prevent you accidently speeding.

 

Dave

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Guest jstead

Most cars I have checked (with GPS and timing along known distances) are up to 10% fast. But in fact the error changes as the tyres wear and the circumferance reduces.

 

------------------

John Stead

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This has been discussed at length before in technical parts of this forum (the speed measurement question - not the how to carry a GPS while skiing) - and as I recall, it's not a simple answer because of the way in which a GPS calculates its position...this could get v interesting, but for the correct answer (which I don't know) I'll get quite technical too.

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Ah ha - found it....was in a response to whether GPS' use position findining difference calculation or doppler shift to calculate velocity:

 

"They use both methods.. position and doppler:

http://joe.mehaffey.com/gpsspeed.htm

From the NAVSTAR GPS User Equipment Introduction document Section 3.7:

 

GPS receivers typically calculate velocity by measuring the frequency shift (Doppler shift) of the GPS D-band carrier(s). Velocity accuracy can be scenario dependent, (multipath, obstructed sky view from the dash of a car, mountains, city canyons, bad DOP) but 0.2 m/sec per axis (95%) is achievable for PPS and SPS velocity accuracy is the same as PPS when SA is off.

 

Velocity measured by a GPS is inherently 3 dimension, but consumer GPS receivers only report 2D (horizontal) speed on their readout. Garmin's specifications quote 0.1mph accuracy but due to signal degredation problems noted above, perhaps 0.5mph accuracy in typical automobile applications would be what you can count on.

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I drive a 1993 Cavalier, and for work drive a Citroen Relay van. (White as well!)

Both vehicles show about 86/87mph when my etrex shows 80.

Oops, officer......I REALLY meant 70mph !!!

 

Honest !

 

GAZ (Carlisle)

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I have managed to successfully use an etrax summit in a jacket breast pocket whilst snowboarding last winter (give or take one or two coverage drop outs). The advantage of the pocket is that as most snowboarders know you tend to spend more time rolling around in the snow than our more conservative skiing brethren [wink] and are therefore less likely to lose your GPSR unit. Zcat.

 

[This message has been edited by zcat (edited 10 January 2002).]

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Guest jeremyp

Regards the difference between GPS and car speedometers. Car speedometers are legally allowed to be up to 10% fast AFAIK, but not slow at all. As no car speedometer is particularly accurate, so most manufacturers aim at 5% fast to give themselves a margin either way. Interestingly, the speedo on my car seems to be consistently 5 mph fast ie. if I'm doing x mph according to my GPS the speedo registers x + 5 mph.

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Guest jeremyp

I have been spawled across the slope on many occasions with a velocity greater than zero, sometimes *much* greater. Usually on these occasions, my equipment (skis, poles, sunglasses etc) is also sprawled across the slope often not attached to me and with different velocities. That's why I don't think it's a good idea to attach your GPS to a ski pole.

 

I'm off for a week in Tignes on Saturday with my eTrex so I'll report back in two weeks time.

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Guest davehinns

Skiing with GPS - hum perhaps a possibility of Garmin introducing a new mount onto a ski pole icon_smile.gif

 

Following recent dashing on my motorbike I struggled with the GPS, having to fit it in the clear pocket on my tank bag, but battery life is poor, so I need to find someway of mounting it, weather protected, and supplied from the bikes power.

 

As for Car Speedo's - one of my vehicles is a Capri, not known for accurate speedos, interestingly because with snowchains fitted the speedo underread by 0.03% so was not allowed, they had to go to the next gearing which put it 8% faster! Go figure those rules.

 

Anyway, mines got several mods so I checked it against my GPS. Indicated 100mph was really 96mph, indicated 70mph was 69.

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Guest davehinns

Skiing with GPS - hum perhaps a possibility of Garmin introducing a new mount onto a ski pole icon_smile.gif

 

Following recent dashing on my motorbike I struggled with the GPS, having to fit it in the clear pocket on my tank bag, but battery life is poor, so I need to find someway of mounting it, weather protected, and supplied from the bikes power.

 

As for Car Speedo's - one of my vehicles is a Capri, not known for accurate speedos, interestingly because with snowchains fitted the speedo underread by 0.03% so was not allowed, they had to go to the next gearing which put it 8% faster! Go figure those rules.

 

Anyway, mines got several mods so I checked it against my GPS. Indicated 100mph was really 96mph, indicated 70mph was 69.

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Guest ighorsey

There is another potential problem with mounting your receiver onto your ski poles, as well as the risk of losing it.

 

Yesterday, I went for a walk around the village where my parents live, and took my Garmin Venture with me. I kept a hold of my unit in my hand, as I was showing people what information I could get from it.

 

Now, when I walk, I swing my arms (almost Monty Pythonesque really) and this had the affect of reducing my speed. When I was walking and swinging my arms, it registered 1.9MPH, but when I walked with the unit held in front of me, it registered 2.9MPH.

 

It also gave me a maximum speed at one point of 16MPH, and I never even broke into a jog!

 

I reckon that my arms moving cause the inaccuracies, as it is either moving forwards faster than my body, or moving in the opposite direction to the way I am walking. I figure that you would get the same problem if it was mounted on a ski pole.

 

Anybody care to back me up on my theory or propose another?

 

Anyway, I'm a snowboarder, so I'm looking at ways of mounting my unit on the board (maybe using a car mobile phone holder?)

 

Cheers

 

Ian

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I have comapred my GPS speed readings with my bike computer speed readings whilst cycling. I know my bike computer is accurate and my GPS showed my speed to be within a a few tenths of a mile per hour of what my bike computer said.

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Guest jeremyp

I'm back from my holiday in Tignes (snow was extemely bad most of the time, so my skis now have big holes in them).

 

My GPS unit was a big hit. I used it to try and monitor speed, distance travelled, ascent and descent. There were some issues with most of them. Firstly, when you're skiing you don't have time to monitor it most of the time and there are several areas where it was not possible to get a GPS signal e.g. at the bottom of the Val D'Isere valley (quite steep sided) and all enclosed lifts especially the two that go through tunnels in Espace Killy. Also, when you're skiing, you spend a lot of time on lifts which travel only between about 5 and 10 mph, thus trip meter stats like average speed and distance travelled are greatly distorted unless you turn off your GPS when on lifts.

 

The max speed stat, however, was great fun. There is a black run with a long run out back to the resort which you have to schuss from a long way up if you don't want to walk. I measured 105km/h on this run (about 65mph). I'm going to get a crash helment before my next skiing holiday.

 

BTW, I kept the GPS in my jacket pocket which seemed to work pretty well. One of my poles was broken when an out of control snowboarder collided with me (I was stationary at the time), so there's another reason not to attach your receiver to a pole.

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Guest ighorsey

e case coming loose (not a problem now I've riveted it!) it worked really well.

 

If anyone would like to see a photo, let me know and I will try and get a photoshoot done, together with some action photos when I'm in France.

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Well I can answer my own question, now that I've just returned from Chamonix. Quite agree with the points made by jeremyp, however I did actually find that my Vista was exceptionally good at recording everywhere I travelled during the day. Each time I took it out of my pocket (top pocket on front of ski jacket) it seemed to have plenty of satellites in view, and the track logs were unbroken 95% of the time. Really pleased with how well it worked.

 

At one point, high on an open mountain, it had 11 satellites in view. My max speed was 53 mph (on snowblades) so you win on that one, jeremyp !!

 

As for snow, well it never stopped all day Thursday, hence Friday - with continuous blue skies - could only be described as an exceptional powder day. I'm sure many of you know what I mean. The boarders were in heaven.

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Guest DaveGeo

I arrived back from Chamonix last night. Skiing was great with a big dump of snow on Tuesday night and all day Wednesday. Was able to ski Thur morning with clear skies :-)

 

I do not think my e-trex was accurate on max speed. I think it is pretty accurate for distance travelled though.

 

I believe the problem lies with keeping the gps in a jacket pocket. What I did was to start up the e-trex wait for it to log on and become accurate, normally six or seven satellites and then put it in a front unpadded jacket pocket. Most of the time my max speed was between 35-40 mph but a couple of times it recorded 55-60 with a max of 62.7 mph. I would say that I wasn`t going any faster than normal at these peaks.

 

I think it is down to poor reception in the pocket and the gps doing its best with the limited information it has.

 

Any comments ?

 

Dave

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Guest ighorsey

I have had a simillar experience with max speed readings on my eTrex Venture.

 

I was coming back from the Isle of Man to Heysham on Wednesday on the ferry, and I was stood at the back under one of the lifeboats, so reception was about 6/7 satellites and fluctuating as I walked around on the deck.

 

Our average speed was 21 mph, but at one point the GPS registered a maximum speed of 161mph. I think I would have felt the sudden change in speed......

 

It could be that these inaccuracies are a result of satellites suddenly being lost, but I don't know any of the science or maths to prove it.

 

Ian

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Guest DaveGeo

Im glad it`s not just me then.

 

On the plane on the way back I recorded 480mph when a few seconds before and after we were going 396mph. Also once in my car I have recorded over 1000mph (I don`t think even a speed camera would catch that!!)

 

Would be interesting if anyone has a more technical explanation.

 

Dave

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Guest jeremyp

The rumour is that UK standard speed cameras will not catch you if you are doing more than about 300mph.

 

As regards GPS, I have occasionally seen sideways jumps in track logs and I logged the position of my chalet in Tignes from the bedroom window (I was surprised to get a signal at all) and it turned out to be wrong by nearly a kilometre.

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Guest dylanhayes

My own experience with walking and cycling has found that the top pocket of a small rucsack works really well especially if it is packed in such a way to ensure the GPS faces upwards rather than backwards. In this possition the unit gets a good view of the sky, whereas in a jacket pocket the sky is often obscured by one's own body especially if you lean forward even slightly, my own experience of skiing would seem to suggest a similar posture is adopted on those occassions when I'm not sprawled across the slope in which case one's velocity is hopefully 0.

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