# Top Speeds true or false?



## SnowMotion (Oct 8, 2010)

With all the smart phones and apps out there everyone is getting there top speed. But I feel some people are looking a kph instead of mph b/c I have heard some people throw around speeds in the 60's. My top speed at 6'1 230lbs on an icy east coast trail was 57.5 mph. I thought that was fast untill someone half my size said they hit 63mph. So if you know your real mph top speed share it and let's have a online race. Honor system remember your only cheating yourself...HA


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## snowklinger (Aug 30, 2011)

theres a 5000 page post on this thats only like a week old.

check it out/search function/me lazy


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## poutanen (Dec 22, 2011)

Lol last GPS track said my top speed was 1900 km/h... I love my GPS tracking software (trekbuddy stores .gpx files that I upload to garmin connect), but it has to be taken with a grain of salt. Pretty much every day I'm on the slopes I have a few corrected peaks in the 70-80 km/h range, but I don't consider it valid unless it shows a steady speed instead of just a peak.

Besides, I'm way more interested in seeing where I went on the hill, and looking at my total mileage and vert.

I wouldn't worry so much about top speed. I'm not running gates on my board (anymore) so it doesn't really matter... At the end of the day it's how dead I feel and how big the smile is on my face.


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## AAA (Feb 2, 2008)

I've tried using a handheld GPS that gave real time speed, but didn't record top speed (ie; you had to look at it on the fly). It seemed to give consistent readouts. As I recall, consistent reads were; carving a green run : 27 mph (easy to watch the GPS), carving a blue : 37 mph (harder to take eyes off run to see GPS), carving a black : 47 mph (could barely spare a glance at that speed), faster parts of the black : ?? (couldn't spare a second to look).

It matches dead on with a car's speedometer, too. Seems accurate on a plane, too. Pretty cool to see exactly where you are flying over...at 40,000 feet and 540 mph.


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## hikeswithdogs (Sep 23, 2011)

Ski tracks seems to be pretty accurate\conservative in it's readings.


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## sabatoa (Jan 18, 2011)

Some science minded guy is going to comment about how your size and weight don't matter when it comes to speed. Board length and wax matter more.


/6'2" 250 lbs, 46mph


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## PanHandler (Dec 23, 2010)

Size and weigh definitely matter more than anything.

Roll a boulder and a pebble down a hill at the same time and see which one gets to the bottom first.


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## sabatoa (Jan 18, 2011)

PanHandler said:


> Size and weigh definitely matter more than anything.
> 
> Roll a boulder and a pebble down a hill at the same time and see which one gets to the bottom first.


hmm, I wonder what the factors are. Drop them from the same level and they fall at the same rate.


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## david_z (Dec 14, 2009)

I'm not a physicist but I'd wager a gentleman's bet that a rider's weight is really not very significant; most of us can "point it" and straightline conditions that would destroy a novice rider no matter his size. Board length, snow conditions, wax, rider ability, etc., are probably all more meaningful than weight/mass.

Also, I have heard that these handheld GPS and especially the apps in your smartphone really don't provide an accurate measure of speed in three dimensions; that is, they perform reasonably accurate while tracking your vehicle speed on a (relatively) flat surface street or highway, but once you put yourself on the snowboard at a 30- or 40-degree incline its nowhere near as reliable. 

Case in point I saw someone say their crazy friend hit like 73mph on a Never Summer Evo. I call bullshit on that. 73mph is approaching olympic GS speed (~80 mph) there is no way anyone on this forum is doing that on an Evo. So, take these speed things with a grain of salt.


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## david_z (Dec 14, 2009)

sabatoa said:


> hmm, I wonder what the factors are. Drop them from the same level and they fall at the same rate.


This is only true in a vacuum but I still don't think that the pebble/boulder thing is a good comparison.


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## PanHandler (Dec 23, 2010)

but it is a good comparison. The momentum of a heavier object alone gives it an advantage. Add in wind resistance and the advantage is significant.


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## david_z (Dec 14, 2009)

If the added mass is muscle in the right places yeah perhaps you are on to something. Otherwise, I just don't think it's important but again I'm not a physicist...


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## poutanen (Dec 22, 2011)

david_z said:


> Also, I have heard that these handheld GPS and especially the apps in your smartphone really don't provide an accurate measure of speed in three dimensions; that is, they perform reasonably accurate while tracking your vehicle speed on a (relatively) flat surface street or highway, but once you put yourself on the snowboard at a 30- or 40-degree incline its nowhere near as reliable.


Not sure about the others, but the Garmin Connect website corrects for altitude based on (I think) USGS survey data. It's a simple calculation really, so the website takes the tracklogs uploaded by a Garmin device (or in my case a smartphone using trekbuddy to record a .gpx datalog) and corrects it.

I'm a bomber, and I think the fastest I've hit according to the GPS (again looking at a pair of points instead of just one peak on the graph) would be about 80 km/h. That seems totally reasonable to me if the GS skiers are doing 80 MPH (125 km/h or so).


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## poutanen (Dec 22, 2011)

PanHandler said:


> but it is a good comparison. The momentum of a heavier object alone gives it an advantage. Add in wind resistance and the advantage is significant.


Didn't you guys do that experiment in grade school where you drop a book and a pencil and they both land at the same time? Mass has nothing to do with top speed. Same with cars. The formula for working out top speed of a car is HP x effective frontal area (which can be reduced with various aerodynamics of course). Top speed of a snowboard would have something to do with slope angle X friction (minimal) X frontal area of the boarder.

I guess what I'm getting at is if we lined up a few of us at a starting gate, all riding the same board, with the same wax job, and we were all the same size in frontal area, but not mass, we would all hit the same speed going down the hill.

Otherwise all the ski racers would be 7'0" 400 pound beasts...


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## marlo_df (Apr 20, 2011)

sabatoa said:


> hmm, I wonder what the factors are. Drop them from the same level and they fall at the same rate.


The rolling resistance would be lower for the boulder and the boulder would carry more momentum, there's less slowing it down, therefore it arrives at the bottom first.


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## l burke l (Mar 1, 2009)

67.5 on ski tracks and it was accurate against my speedo in my car


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## dreampow (Sep 26, 2011)

I have no mobile phone because I don't like them. Hence I have never measured my speed. 

I would say I go pretty fast and have never been overtaken on the steeps while going full pelt. I know I am maching when my jacket starts to ripple and flap a certain way.

I feel satisfied when I get good turns in, or a sweet grab off a natural feature or a nice clean 360 nailing the landing and for the most part no one else will ever see those turns or the lines because I am off the beaten track (and don't take much footage).

I know when I got it right and thats a great buzz.

For me its the quality of my boarding not the speed or milage that counts.


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## dave1billion (Dec 29, 2008)

Sounds like a challenge that needs empirical proof.

What sized bindings do I need to get to test this for:

A. The boulder
B. The pebble
C. A labrador retriever (got to have a control)


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## MarshallV82 (Apr 6, 2011)

They are fairly close I think.. 

60-70 MPH is not that uncommon for boarders, honestly..
nice flat hard-pack groomers, it's not really that scary. 

Skiers even go faster.


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## JeffreyCH (Nov 21, 2009)

PanHandler said:


> but it is a good comparison. The momentum of a heavier object alone gives it an advantage. Add in wind resistance and the advantage is significant.


My guess is a lighter rider is going to accelerate faster because of less resistance ie:wind and friction on the surface. While a heaver rider is going to reach a higher top speed over distance. Might be a pertinent comparison here... 

MythBusters: Toy-Car Top-Speed MiniMyth : Video : Discovery Channel


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## snowklinger (Aug 30, 2011)

Stick to your day jobs you retarded flock of internet scientists!

I like how everyone has an "opinion" about the laws of physics.


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## david_z (Dec 14, 2009)

MarshallV82 said:


> They are fairly close I think..
> 
> 60-70 MPH is not that uncommon for boarders, honestly..
> nice flat hard-pack groomers, it's not really that scary.
> ...


Olympic-caliber skiers go faster than that, but I don't the run-of-the-mill two planker is going 80+ mph on the regs. Likewise, yeah can a snowboarder go 70mph? Sure. But the average boarder will never even come close to that speed.


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## Leo (Nov 24, 2009)

PanHandler said:


> Size and weigh definitely matter more than anything.
> 
> Roll a boulder and a pebble down a hill at the same time and see which one gets to the bottom first.


The pebble will go slower only because it has less momentum. This means every little bump and obstacle will slow it down. On a perfectly smooth hill with no wind resistance, the pebble will roll down the hill just as fast as the boulder.

Momentum = Mass x Velocity

More momentum does not equal more speed. In general terms, it just means it's going to be harder to stop. A car and a bike can go the same exact speed yet the car will be much harder to stop. This is where that phrase "the bigger you are, the harder you fall" comes from.

Now a pebble compared to a boulder is extreme. Much more extreme than comparing someone that weighs even a hundred pounds less than another. The difference is likely negligible.

I think surface area of snowboards matter most. Bigger people usually ride bigger boards hence they tend to go faster. You also have to factor in skill.

Snowolf and David Z ride around the same length snowboards. From what I've seen Dave hit and from what Snowolf has posted, they are neck-and-neck in terms of speed even though Snowolf weighs about 20lbs less. Dave rides a 156 and I ride a 158 and yet Dave still goes faster than me. Not because he weighs more, but because he's more skilled than I am.


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## Leo (Nov 24, 2009)

david_z said:


> This is only true in a vacuum but I still don't think that the pebble/boulder thing is a good comparison.


If you get highly technical with measurements, yes what you said is true. However, drop a pen and a stapler yourself right now from standing height. The difference will be so minute that you won't even notice. They will appear to fall at exactly the same rate.

If you drop them from a significant height, then stuff like wind resistance will come into play. Also depends on the items. A feather obviously won't fall at the same rate from any height (outside of a vacuum) as a pen because it inherently "floats".


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## Snowrat (Jan 3, 2012)

I'm not a physicist either, but I took physics in college a LOOOONNNGGG time ago, and I think this is correct:
Final Velocity = Initial Velocity + (Acceleration x Time)
Acceleration = Force / Mass

So, if I remember the math equations correctly, all other things being equal, more weight will cause a REDUCTION in final speed. Of course, all other things aren't equal. The actual forces applied are complicated. As others have said, wax, clean carving and snow conditions all affect friction. Body position affects wind resistance. I'm siding with all the posters that said it's more about skill.


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## Leo (Nov 24, 2009)

Snowrat said:


> I'm not a physicist either, but I took physics in college a LOOOONNNGGG time ago, and I think this is correct:
> Final Velocity = Initial Velocity + (Acceleration x Time)
> Acceleration = Force / Mass
> 
> So, if I remember the math equations correctly, all other things being equal, more weight will cause a REDUCTION in final speed. Of course, all other things aren't equal. The actual forces applied are complicated. As others have said, wax, clean carving and snow conditions all affect friction. Body position affects wind resistance. I'm siding with all the posters that said it's more about skill.


Your memory is faulty sir. Weight does not affect speed at all. A hammer and feather will fall at the same rate on the moon.

If you are talking about wind resistance being greater on a heavier object, there are far too many factors to discuss here. Aerodynamics, density, etc...

Again, weight plays no role in speed. The only thing that matters with weight is the force required to get the momentum started. This only applies on flat surfaces. In a free-fall or once the momentum has started, no affect on speed.


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## Cr0_Reps_Smit (Jun 27, 2009)

i havent been able to clock myself going the fastest i can go yet but my speed going into the medium jump at my mtn is about 35 mph and 55mph going down a medium pitch on a run. that was on my proto too.


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## david_z (Dec 14, 2009)

he didn't say weight he said mass, and that formula for Acceleration = F/m is 100% correct.


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## Leo (Nov 24, 2009)

Snowrat said:


> So, if I remember the math equations correctly, all other things being equal, *more weight will cause a REDUCTION in final speed*.


Dave, I require 5 Hail Zeus's for your blaspheming.


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## Nefarious (Dec 26, 2010)

Screw Zeus...We need Ullr.


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## david_z (Dec 14, 2009)

Leo said:


> Dave, I require 5 Hail Zeus's for your blaspheming.


Ahhh I was looking only at the _equations_. Nevertheless, I shall vindicate myself twofold:

@ Leo: In normal earth gravity, weight = mass.

@ Snowrat: "all other things being equal, more weight will cause a REDUCTION in final speed." This is FALSE but I think you just used your wrong words. More _mass_ will (c.p.) cause an object to accelerate less. This doesn't cause a "reduction" in speed (e.g., deceleration) , it simply does not allow to obtain higher speed.


Ullr and I are not on speaking terms anymore.


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## CheeseForSteeze (May 11, 2011)

David Z brings up an interesting point in how GPS transponders are viewed to be moving in a 2-dimensional plane but we really ride down mountains that are not parallel to such a plane. In that case, the velocity (vector) is projected (dot product) onto such a parallel plane and is reduced as the "z" component is neglected. Thus, the speeds seen are actually conservative and true velocity should be higher than what the tracking unit reads. However, we don't know what algorithms these GPS units use to calculate speed. There very well could be some sort of calculation to compensate for this "planar projection" effect which actually overcompensates the conservative value making it higher than it should be.

GPS transponders also vary widely in quality. The accuracy of the clock largely effects the accuracy of ability of the unit to locate itself since it does so by quadangulating off 4 different satellites which are in motion against itself on the surface of the earth (the earth is in motion, rotates and the unit itself is also in motion) and uses time stamps to complete the quadangulation. Since the signal travels at near light speed, small errors in the clock can make the unit misposition itself. The worse the clock, the worse the positioning. This would compound itself in velocity calculations as velocity is just the first time derivative of position with respect to time.


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## Sean-h (Oct 21, 2011)

To be honest, I would rather not know how fast I ride... There is a radar (speed trap) here, that if you want, will tell you your speed, I have yet to pass it, or to stop and see what it reads. Generally, the burning in my legs is indicative of how near death I just was.


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## bntran02 (Feb 26, 2012)

CheeseForSteeze said:


> David Z brings up an interesting point in how GPS transponders are viewed to be moving in a 2-dimensional plane but we really ride down mountains that are not parallel to such a plane. In that case, the velocity (vector) is projected (dot product) onto such a parallel plane and is reduced as the "z" component is neglected. Thus, the speeds seen are actually conservative and true velocity should be higher than what the tracking unit reads. However, we don't know what algorithms these GPS units use to calculate speed. There very well could be some sort of calculation to compensate for this "planar projection" effect which actually overcompensates the conservative value making it higher than it should be.


I should also point out that it depends on the frequency in which a GPS location is detected. If it is not frequent enough then the distance will be measured as several straight line segments instead of a single curved route which can be significantly longer.


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## CheeseForSteeze (May 11, 2011)

Yep, that would be the "planar projection" error. It would be interesting to see if you could take readings during a dive of indicated airspeed, GPS speed and pitch. The air speed indicator (V) should (if there is no head or tailwind) read GPS indicated speed (v) divided by the cosine of the angle of the pitch (a) relative to the horizon. Do the artificial horizon's typically read in degrees?

Or, V = v / cos(a).

Since the cos of any angle is always less than 1, this is why the GPS speed is always lower than the indicated air speed, assuming indicated airspeed is close to true speed. No wind.

Cops deal with the same thing when they radar you. If they don't radar you when you are driving straight at them, the speed will always be reduced by some factor because radar works on the Doppler principle.

Interestingly, higher speeds won't affect the amount of error between your true speed and GPS indicated speed, assuming main source of error is this projection error. A Cessna @ 140 knots, a 767 at 460 knots, the Concord at 1800 knost and a snowboarder all diving at a 45 degree angle would all indicate approximately 70.7% of their true speed as indicated on GPS (cos (45 deg) or 1/sqrt(2) )


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## david_z (Dec 14, 2009)




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## mkgntal (Feb 2, 2014)

snowklinger said:


> Stick to your day jobs you retarded flock of internet scientists!
> 
> I like how everyone has an "opinion" about the laws of physics.


:eusa_clap: This deservers to be print on a t-shirt or something, so true...


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## Bones (Feb 24, 2008)

My ski tracks app seems pretty accurate in the car for speed as do my friend's android and iphones running the same app. On the hill, it is a different story. 2 of the 5 of us ski and they're good and plenty fast. The other 3 board and we're all about the same speed. 

At the end of the day, we're all over the place in terms of top speed for the day. We've tracked it back to specific runs, looked at Go-pro footage and still can't see where, even briefly, one of us was going 50 kph faster that the others.


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## kalev (Dec 17, 2013)

Can the internet scienticians explain why bobsleds have weight restrictions (and generally people cheat by adding more weight to the sled)?


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## CassMT (Mar 14, 2013)

when you get how gps works, it's obvious how these trackers could be +/-10mph, regardless what they claim for accuracy...


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## Kevin137 (May 5, 2013)

I have a Contour+2, Oakley Airwaves, and an iPhone 5s running Alpine Replay, and they generally all come in within .5kmh of each other over the course of a day...

Now the App is not as good as the others, but since the Airwave and the +2 have GPS mapping you can actually compare exact positions on mapping with speed records to see any differences...

I still have a top speed of 107 KMH or 67 MPH and that was way fast enough for me...


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## Booo! (Feb 14, 2014)

kalev said:


> Can the internet scienticians explain why bobsleds have weight restrictions (and generally people cheat by adding more weight to the sled)?


Just a hunch, but I know skates (what the bobsled runs on) work because they compress the ice and turn it into water (just under the skate's edge of course), since water is more dense than ice. I guess the more pressure you put on the skate, the faster it will turn ice into water?

And just to add to this awesome excercise in physics "opinions," don't forget about friction. :laugh: More weight = more friction. That's why the boulder vs pebble comparison doesn't work. Snowboarders usually slide on the snow, they don't roll. I said usually.


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## david_z (Dec 14, 2009)

Booo! said:


> Just a hunch, but I know skates (what the bobsled runs on) work because they compress the ice and turn it into water (just under the skate's edge of course), since water is more dense than ice. I guess the more pressure you put on the skate, the faster it will turn ice into water?


Not exactly. That theory doesn't explain how ice skating is possible even at very cold temperatures. From wiki:

A skate can slide over ice because the ice molecules at the surface cannot properly bond with the molecules of the mass of ice beneath and thus are free to move like molecules of liquid water. These molecules remain in a semiliquid state, providing lubrication​
Ice skating - Wikipedia, the free encyclopedia

IOW, while melt may occur, it is not a necessary condition for ice skating.


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## Redline (Jan 14, 2014)

The app I use is spot on with my car on the flats and in the hills. It claims I've hit 69.3 mph on a 67cm lib TRS. I can't scientifically speak for it's accuracy but it felt like I was hauling ass. I'm 6'3" and ~220 lbs


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## kenshapiro2002 (Feb 1, 2011)

Using Ski Tracks, this 61 year old kid hits the low 40s all the time, and I'm NOT going to be going any faster!


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## f00bar (Mar 6, 2014)

The part of the equation that most are leaving out and that is the really important thing here is inertia. Everything else being equal, the more mass the more inertia. Inertia is the measure of an object to resist a change in velocity.

This is why in a vacuum mass is taken out of the equation when things are dropped because there is no friction and inertia doesn't matter. Start adding a force trying to slow you down and that force has less effect on heavier objects.

Or, think of it this way. It's not that heavier goes faster as much as the lighter are more easily slowed down. Primarily by snow friction. And this doesn't get into the little stuff like larger people may have larger boards which may actually distribute their weight to be less lbs/in^2 better, and a myriad of other things.


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## Argo (Feb 25, 2010)

Shit, I ride every day and could care less how fast I'm going..... Who cares? Lol.... I'd rather have a heads up race. One in pow, one on groomer..... Unfortunately my 14 year old will beat us all. 

So when's the race? SBF banzai snowboard race......


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## Lstarrasl (Mar 26, 2010)

Im always down for a race if anyone wants to put their money where their mouth is...
:cheeky4:



But I can't do it at any Vail resorts because I got my passed pulled for riding too fast...:thumbsdown: (I only got up to 70 that day)


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## SnowDogWax (Nov 8, 2013)

Love speed! That being said any top speed on my Iphone is discarded unless its confirmed with another run down the same slope.

My top speed average of three consecutive runs is 58.6 mph. This I consider to be my top speed.

Switch is getting close to 50mph :dizzy:

All my higher single speed runs I consider garbage.


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## LuckyRVA (Jan 18, 2011)

I've found the iphone gps to be fairly accurate except for a few situations. One instance in particular I biffed in spectacular fashion and my ski tracks app listed my top speed as 325 mph on that run. :dizzy:


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## behi (Feb 27, 2013)

LuckyRVA said:


> I've found the iphone gps to be fairly accurate except for a few situations.


How would you know?

Ski tracks is calculating speed based on position/distance measurements, which are way too inaccurate for skiing/snowboarding. For accurate speed data, a doppler effect based speed measurement is required. I don't know if any phone GPS supports that, but Garmin Etrex hiking GPS units do.


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## LuckyRVA (Jan 18, 2011)

Fair enough, maybe accurate was the wrong term to use. However, my high speed runs are consistently about the same, within a few mph of each other. A buddy of mine I ride with will get very similar results on his phone that I get on mine (this is riding together side by side). Additionally, I've tested it in the car and the speed shown on my iphone matched up with my Garmin gps.


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## Bones (Feb 24, 2008)

A lot of the new handheld GPS units are coming out with barometric pressure altimeters, 3D compasses and the ability to access the Russian GPS (more links) in part to give more accurate reading in mountainous areas. 

In short, if your phone consistently gives you a speeds of 70mph, then yes, you're probably going pretty quick. If you get a very high one-time peak speed, then view it with scepticism. In either case, comparing phone readings between different phones or different locations or different times is a fools game.


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## SnowDogWax (Nov 8, 2013)

behi said:


> How would you know?
> 
> Ski tracks is calculating speed based on position/distance measurements, which are way too inaccurate for skiing/snowboarding. For accurate speed data, a doppler effect based speed measurement is required. I don't know if any phone GPS supports that, but Garmin Etrex hiking GPS units do.


Think i'll start wearing my huge GPS garmin watch + chest band. Retro fit to my helmet a sirus radio antenna/reciever then connect it via bluetooth. Activated with a voice read out the MPH it will either sing, sports report, or use any of the garmin voices to my ear buds. All would then be monitored by my iPhone and a g-force probe attached to my face with an auto electrical shock at 50-60-70 MPH. Would that then be accurate:dizzy:


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## hardasacatshead (Aug 21, 2013)

No small GPS unit is going to be precise. No matter how much you pay they're only going to position you to within 15m at best provided you've got at least 4 satellites in view. So the speed readings are questionable at best. 

I'm pretty sure iphones etc use radio signals in conjunction with GPS to triangulate your position. 

I did my honours thesis on high precision GPS. I improved the design of a guidance system for dozers stripping overburden in open cut mines to allow them to strip waste material to within about 50mm of the orebody. It's pretty complex and you need a lot of hardware to get to those extremes. A Garmin hand held unit ain't gonna cut the mustard I'm afraid and an iPhone is in the same boat.


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## HUNT24/7 (Feb 8, 2010)

I clocked 68mph with my Garmin GPS


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## behi (Feb 27, 2013)

hardasacatshead said:


> No small GPS unit is going to be precise. No matter how much you pay they're only going to position you to within 15m at best provided you've got at least 4 satellites in view. So the speed readings are questionable at best.
> [...]
> A Garmin hand held unit ain't gonna cut the mustard I'm afraid and an iPhone is in the same boat.


It does with doppler-based speed measurements (0.5 mph accuracy is easily possible). E.g. for the tiny GT31 GPS logger with SIRF 3 chipset there is a test here:
http://nujournal.net/SDOP.pdf

Garmin is using the same doppler-based speed measurements in the high sensitivity etrex units.


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## lab49232 (Sep 13, 2011)

Again it's been said once or twice before already but what people aren't considering is linear distance vs actual distance traveled. GPS will almost always match your car as you aren't driving down 45 degree slopes in your car. But picture it in the terms of "as the crow flies" Basically your car you travel 2 miles east to west over the face of the earth as viewed from a satellite, it's easy to measure speed. However when snowboarding, you may travel two miles down hill, but maybe only one mile east to west. In "as the crow flies" it may look like you traveled a mile even though if you took a tape measure and laid it on the ground it would measure two miles. Without 3d veiwing (which your phone *does not* have) it will be impossible to be precise. Readings can be consistent and used to check if you went faster or slower than before but for hard numbers of your actual speed compared to say a car the measurements will be useless.


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## I need a name (Mar 5, 2009)

73mph on Dave Murray Downhill at whistler with my zeals. Going faster? No thank you. Only did it because I had first tracks on a sunny groomed day. I topped it out hard right there, peeked down at the mph and it didn't budge. Thank you T rice for holding up at these speeds. 



Anyone that has been down dave murray knows what happened when I came up to one of the headwall that has moguls on it.....


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## f00bar (Mar 6, 2014)

lab49232 said:


> Again it's been said once or twice before already but what people aren't considering is linear distance vs actual distance traveled. GPS will almost always match your car as you aren't driving down 45 degree slopes in your car. But picture it in the terms of "as the crow flies" Basically your car you travel 2 miles east to west over the face of the earth as viewed from a satellite, it's easy to measure speed. However when snowboarding, you may travel two miles down hill, but maybe only one mile east to west. In "as the crow flies" it may look like you traveled a mile even though if you took a tape measure and laid it on the ground it would measure two miles. Without 3d veiwing (which your phone *does not* have) it will be impossible to be precise. Readings can be consistent and used to check if you went faster or slower than before but for hard numbers of your actual speed compared to say a car the measurements will be useless.


While this may seem to make sense and apply it's simply not true. The GPS constellation is arrayed 3 dimensionally. The whole system works in 3 dimensions all the time. Your car just happens to be going in two, the vector calculations are exactly the same. Position is determined in x,y,z each with the same accuracy. GPS is ultra sophisticated and thought out, of course it can handle 3 dimensions, planes and drones, and bombs hitting their target rely on this. It's one of the few every day things that rely on Einstein's theory of relativity to work in how it factors in the Earth's gravity into the timing of the GPS signal from each satellite, time actually runs slower on Earth than the satellite so that has to be accounted for to keep signals in sync.

That said there are some difficulties introduced. Mainly the fact that you are in the mountains and blocking some number of satellites because of it. The less satellites you can see the less accurate you're going to be. The extreme case being the concrete jungle of a city where gps can totally go to crap on you at any time. Accuracy differences with only 3-4 satellites compared to 10 is huge.


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## wrathfuldeity (Oct 5, 2007)

Irregardless of measurement type or accuracy; the biggest factors are angle of slope, slope conditions and wind resistance...like if you got a head or tail wind.


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## tokyo_dom (Jan 7, 2013)

The reason for inaccurate measurements is almost definitely due to signal drop/resume. Gps positioning can get a bit sketchy when you only have a couple of satellites in view. Leading ski tracks/etc to think you are at point A, when in reality you are 50m from there. Then the gps signal recovers and brings you to your correct position. Ski tracks just sees that your position has gone 50m in under 1 second, and bam you have a new top speed. Its important to look at the stats for that instantaneous speed to see if it was when you were bombing it or not...


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## surfinsnow (Feb 4, 2010)

I tracked Sundown in CT on Thursday. Small (very small) hill, only 750'. The Snowcru app said I hit over 47 mph. Okay, but nothing stellar. Friday I went to Catamount, 300' more vert with a couple of steeps. Snowcru said I never topped 43 mph. I'm not buying it. I know I was riding much faster at Catamount than I was at Sundown. Longer trails, steeper steeps, faster runs. I'm not too sure about the accuracy of these things.


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## SnowDogWax (Nov 8, 2013)

I ride at JayPeak, VT more vertical longer runs than SevenSprings, PA same thing so I'm with you on accuracy. I use SkiTracks App, would be interesting be with a group of five friends all with smart phones testing to see the accuracy.


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## neni (Dec 24, 2012)

Was tracking a hack with SkiTracks to monitor the trail on the map and get an idea on the distance. On one "descent run" of that trail, we had a top speed of 67mph :blink:

For those not familiar with horses: top speed of the fastest horses is up to 55mph (Quater horse on full galop in a flat race track).

BTW: If that wasn't clear enough: That "descent run" was while going down a hill path, in walk pace, going 5mph at the most in reality.


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## f00bar (Mar 6, 2014)

neni said:


> Was tracking a hack with SkiTracks to monitor the trail on the map and get an idea on the distance. On one "descent run" of that trail, we had a top speed of 67mph :blink:
> 
> For those not familiar with horses: top speed of the fastest horses is up to 55mph (Quater horse on full galop in a flat race track).
> 
> BTW: If that wasn't clear enough: That "descent run" was while going down a hill path, in walk pace, going 5mph at the most in reality.


Mountains are tough, you lose satellites, you lose accuracy. At best civilian is about 3m. So imagine one sample shows you off by 3m up the hill, the next 3m down the hill and whamo, you've miraculously traveled an extra 6m, which is a huge amount given the sample frequency. The GPS tries to filter things, but filtering is good for trends, not a fastest time.

There are actually 2 other GPS systems available for use to augment the global. One by the coast guard, the other the transportation department. Unfortunately most areas aren't on ships in the ocean or near a highway so these typically aren't available on the slopes so results will be shoddy at best for speed, though it will get you home if a bear chases you into the woods and you get lost.


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## Casperftw (Mar 1, 2014)

2 of my friends and myself use Skitracks and we think its pretty accurate we have all reached different speeds on the internet the best speed i have reached is 51.8 MPH if you don't know you can change this to KPH in settings and i only weight 150 pounds using a freestyle board just straight line from the top until i got scared and speed checked haha. my friend hit 63.4 and hes around 200. alot of people hitting similar speeds on the mountain we have been riding the last 2 weeks


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## LuckyRVA (Jan 18, 2011)

Casperftw said:


> 2 of my friends and myself use Skitracks and we think its pretty accurate we have all reached different speeds on the internet the best speed i have reached is 51.8 MPH if you don't know you can change this to KPH in settings and i only weight 150 pounds using a freestyle board just straight line from the top until i got scared and speed checked haha. my friend hit 63.4 and hes around 200. alot of people hitting similar speeds on the mountain we have been riding the last 2 weeks


I read this 3 times and still not sure what you're trying to say. :icon_scratch: Punctuation is key.


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## F1EA (Oct 25, 2013)

If you actually needed an accurate top speed.... somebody else would be taking it for you with an accurate device.


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## surfinsnow (Feb 4, 2010)

LuckyRVA said:


> I read this 3 times and still not sure what you're trying to say. :icon_scratch: Punctuation is key.


:laugh:

I didn't quite get it, either. Apparently he thinks the satellites know if he weighs more than his friend. Or something.


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## SnowDogWax (Nov 8, 2013)

^^^^
He is able to change settings while going 51MPH even though he is only 150LBS he got scared straight haha his friend is 63 or 200 and he only ridden for two week…..


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## Argo (Feb 25, 2010)

I think he snowboards really fast on the internet.... Is that like surfing the net?


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## Todd2002 (Jan 22, 2013)

Speed depends on how much guts you have. Fear is the desiding factor. Point it down the mountain and go as fast as gravity will take you. A friend went 55 at snowshoe and got passed by a skier running 69. Speed is speed. If you want to go fast grow a pair and turn it loose.


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## hardasacatshead (Aug 21, 2013)

Shit. All those years studying physics and that's the answer. Well I'll be a monkey's father's brother.


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