How fast do you really go while carving?

[CarvingScooby]

How fast do you really go while carving?

EC all the time, no straight line.

Timing maybe 1 - 1.30 minutes off: @ least a minute from putting IPhone back & wear my gloves thn another 30 second - took off gloves, pull out and switch it off. Why taking so long?;the heavy duty "Otter" case on the IPhone made it harder to slide in and make it worse the rubber outer shell is sticky.

RT

[philw]

I shot some speed snowboarding once. The world record's about 200km/h - 125 Imperial units per hour. You can't stand up at those speeds, and you're running on a specialist slope which people approach with axe and crampons or roped up. The timing section's a small part of the course, followed by a huge deceleration zone which takes up about 2/3 of the length of the course. If you fall at the very end of that, you'll hit the inflatable barriers at speeds which look much faster than anyone you ever saw crash at a resort. Board lengths are 2.30m or so and they don't really turn (you steer with your fingers).

If you think about a GS race compared with normal piste riding, there's a huge difference in speed. The same is true once more for speed snowboarding, in my view.

In mountains and forests with variable speeds even specialist GPS has a number of challenges. It all depends how the device deals with them. Some of them give erroneous maximum speeds. Some "ring". What period are they averaging "speed" over? What do they do if they do not have valid position information covering that period? What happens if you use two GPS receivers of different make (preferably different receivers)?

[Marc H]

Yes, please, let me know when so I can have patrol there to <s>pull your pass</s>, I mean, verify it.

He is. Sure why not. I don't have softies, but maybe with my new SG 163 I'll actually be able to carve a few of the turns on that "flight of the bumblebee" course.

Comp hill isn't the slow area is it

[queequeg]

In mountains and forests with variable speeds even specialist GPS has a number of challenges. It all depends how the device deals with them. Some of them give erroneous maximum speeds. Some "ring". What period are they averaging "speed" over? What do they do if they do not have valid position information covering that period? What happens if you use two GPS receivers of different make (preferably different receivers)?

I think this was covered in a prior thread, but that any speed estimations calculated from smartphone GPS data (and probably 99% of dedicated GPS units) are likely to be very inaccurate for carving. The GPS in your phone can probably give you an accurate readout of your driving speed in a car because you are traveling in a straight line and moving at a pretty consistent speed. As soon as you start weaving left and right as dramatically as a carver does you're going to get very inaccurate readouts; due to the relatively low resolution that the GPS records your movements at (not to mention acceleration/deceleration cycles between the top, apex and bottom of each turn). Chances are also good that the GPS in your phone probably does not take minor changes in altitude into account when calculating speed as well, though maybe dedicated GPS units are better at this.

It all depends upon the quality and frequency of the GPS tracking data, whether or not altitude/topography changes are accounted for in this data, and how thoroughly/correctly the data is interpreted by whatever speed averaging software is involved. I'd bet that the dedicated units are much better than phones, but it probably varies dramatically from unit to unit.

[BlueB]

I don't believe smartphone would do quite a good job. I'll try, though...

However, I always want to go as slow as possible, have 0 desire for speed records, at least while carving.

I think that Dave* was once clocked at 50mph by radar gun, on a mellow blue pitch.

[Neil Gendzwill]

I think this was covered in a prior thread, but that any speed estimations calculated from smartphone GPS data (and probably 99% of dedicated GPS units) are likely to be very inaccurate for carving.

There's simply no way they would be accurate enough for carving. Maybe straight-lining. Dedicated Garmin running watches sample sporadically by some algorithm that figures out when they should take a sample, but no faster than once every few seconds. I have no idea if other devices are better, but if they sampled fast enough to accurately track a fast-moving carver then storage space would rapidly become an issue.

[MUD]

I think this was covered in a prior thread, but that any speed estimations calculated from smartphone GPS data (and probably 99% of dedicated GPS units) are likely to be very inaccurate for carving. The GPS in your phone can probably give you an accurate readout of your driving speed in a car because you are traveling in a straight line and moving at a pretty consistent speed. As soon as you start weaving left and right as dramatically as a carver does you're going to get very inaccurate readouts; due to the relatively low resolution that the GPS records your movements at (not to mention acceleration/deceleration cycles between the top, apex and bottom of each turn). Chances are also good that the GPS in your phone probably does not take minor changes in altitude into account when calculating speed as well, though maybe dedicated GPS units are better at this.

It all depends upon the quality and frequency of the GPS tracking data, whether or not altitude/topography changes are accounted for in this data, and how thoroughly/correctly the data is interpreted by whatever speed averaging software is involved. I'd bet that the dedicated units are much better than phones, but it probably varies dramatically from unit to unit.

Well, now I don't have to worry about bringing my GPS anymore. Sweet!

[Jack M]

There's simply no way they would be accurate enough for carving. Maybe straight-lining. Dedicated Garmin running watches sample sporadically by some algorithm that figures out when they should take a sample, but no faster than once every few seconds. I have no idea if other devices are better, but if they sampled fast enough to accurately track a fast-moving carver then storage space would rapidly become an issue.

At first I want to agree with you, but considering Cuban's and Scooby's results which break 40 while carving, I'm not sure. A slower sampling rate would make me think the GPS reading would be slower than actual, because it wouldn't be measuring your speed along the curved path as accurately. It would appear to the GPS that you covered less ground than you did.

I think we can assume we are carving at least as fast as any GPS will say.

[queequeg]

At first I want to agree with you, but considering Cuban's and Scooby's results which break 40 while carving, I'm not sure. A slower sampling rate would make me think the GPS reading would be slower than actual, because it wouldn't be measuring your speed along the curved path as accurately. It would appear to the GPS that you covered less ground than you did.

I think we can assume we are carving at least as fast as any GPS will say.

This is true ... fewer readings mean it is going to give you a lower speed reading. If the software interpreting the GPS data uses bezier curves between points to approximate actual paths the accuracy will improve somewhat but I doubt that will make much of a difference. Also - if small elevation changes are not among the things recorded or considered by the software (and also at a substantial sample rate) then the carver's speed would be underestimated by an even greater margin.

I imagine you'd probably get a more accurate reading of someone that makes huge GS style turns and is hauling ass than someone who does lots of little SL turns at lower speeds, particularly if the estimation software used bezier curves to predict the actual rider path. You'd probably get better accuracy on a green run than a black.

[Willow 15]

Really, really, really

[MUD]

The more I think about it, the more I want to try my GPS.

I have used it in heavy woods on tight singletrack on my mountain bike. It was as accurate as my friends computer as far as the speeds. The tracking was VERY accurate.

I have also used it in VERY heavy, thick, up and down twisty slow and fast woods on my motorcycle. Once again, did fine in comparison to my friends enduro computer. Don't know about the tracking as it was out first time mapping it.

My unit is a Garmin 60csx.

[kieran]

Really, really, really

really?

[Sultan Guy]

Last season I used my Garmin GPS watch one average morning of carving. Shows 39.6 MPH was the fastest speed. I could go faster but I like to turn too much.

<iframe width='465' height='548' frameborder='0' src='http://connect.garmin.com:80/activity/embed/77982251'></iframe>

[ar(angel]

while riding the 178 Burner last season. Used an app called "SpeedView" on my Android. Hit 42 while letting it run straight, but 38 was the tops while making some big GS type turns. I've seen Cuban ride and have no doubt his speeds are accurate. Downloaded a Grav-o-meter for this season, Trikerdad and Ralaan have been using a g-meter for several seasons now and have some good data.

[leeho730]

Used ski track iPhone app. Top speed 50mph. Average carving speed would be around 14-20 mph.

[Cuban Carving Gooding]

I'm no brain surgeon but .I think it boils down to this. We all ride different styles so speeds will be different. Not to mention A different run at A different resort will change speeds for the same rider. The larger part is how GP works.I know that i have 6-10 plus satellites pinpointing my GPS hand held witch i pulled my data from. Here's the part i don't know. How often each satellite looks at my gps unit. The more they look the more i believe in gps. As you know in my past post I believe in it. But I have read things that cast some shadows. My GPS use was just to see carving speeds. But it opened my eyes to the speeds we all travel on our boards. Faster than I thought (top speeds i have seen from myself and friends). It shows the importance of A helmet. Please be safe.

[kieran]

How often each satellite looks at my gps unit. The more they look the more i believe in gps.

the GPS satellites broadcast a continuous timing signal, along with a signature id and their position in the sky. it's up to your receiver to use the information in those signals to work out where it is.

[philw]

You need to look at the raw data coming out of the receiver to see where and how the interpolation is being done. It has to be done because the receiver needs to tell you where you are, even if it does not actually know at that point in time. I have programmed several receivers and they all behaved differently in terms of how they deal with rapid direction changes and limited signals. All of them interpolate.

The interpolation will "assume" you're "going one way" and predicts your position based on that. So now it has a position which is inaccurate. When more data comes in, your location "jumps" from the incorrectly predicted place to the "better estimate" (which may also be incorrect). So depending on the algorithm used to calculate speed, that can result in wild over-estimates (because you may appear to "travel" very quickly from one place to the other).

So if you think about how interpolation works when the receiver changes direction, you get over not under estimates.

They try to correct for this with various algorithms. So if, for example, you're in a car, then they may reject "outliers" - speeds which are impossible - from their moving window calculation. Better, they generally have geographic (map) data to hand, so they know where the road is... they can use that to improve the interpolation no end.

But you're riding, so none of that is optimised for you. Sadly you may be be slower than you want to believe, possibly in more ways than one ;-)

[Helmut Karvlow]

I love to go fast! especially on my 196. the only fact I have to offer, is just when my helmet starts to whistle and I think I'm flying........Bordy passes me in a flash:eek:

[AutumnOrangeGT]

I had a RipXX app for my android phone that said I hit 60mph on a run once. Unfortunately the same run also said I'd only covered 9 vertical feet... it was a considerable amount more so I'm guessing it might have been a mph or two faster..

[D.T.]

I agree with the above statements that sampling at a slow rate will mean that the top speed per the GPS will be lower than actual.

My data so far this season:

• Day 1: top speed = 39.4 mph, avg. speed = 16.0 mph
  
• Day 2: top speed = 39.6 mph, avg. speed = 15.9 mph
  
• Day 3: top speed = 49.5 mph, avg. speed = 15.8 mph
  

My consistency in average speed, whether accurate or not, tells me that my comfort zone is well defined, at least here in the early season. I'll be interested to see what happen as more terrain opens and the season wears on...

[nigelc]

I have been riding with an android phone in my pocket for two seasons and have used various apps to measure speed. Over roughly 60 days of riding the results always seem to come out that I cruise around with a peak speed roughly 50-55 kmh most of the time , and if I make a special effort to go as fast as possible then I can hit a peak of 97-100kmh while scaring myself ****less. None of this is by straightlining and I get extra speed just by drawing the carves out to a large radius. Peak speed is on the 3rd or 4th turn of the run after which my quads fail and the recorded speeds drop down into the eighties and then lower. I have never tried straightlining - too dangerous!

I have ridden a few seasons ago with Andrea Matteoli - (matiu68 here bomber) with his garmin gps and at that time he was peaking out at around 90-100kmh and I was just managing 55kmh max which on that hill seems scary fast.

What's interesting is I have recorded 70kmh windsurfing - and I was being passed at the time!

[Mellow Yellow]

I go plaid

[dlokshin]

Hi All,

My name is David and I'm one of the founders of AlpineReplay. We've been getting a lot of traffic from Bomberonline, and I thought I'd stop by, say hello, and answer a few questions.

In terms of speed, it's pretty accurate. For most entries, probably to a half mile per hour. A majority of modern chip sets use Doppler to figure out speed, and not a back calculation from two points. For those that don't use Doppler, they heavily rely on something called a Kalman filter which works very well on straight continuous motion, but not as well on dynamical motion like skiing.

We have more than 10mil vertical feet skied on AlpineReplay thus far, and I don't think we have had a single instance of a phone giving data at worse than 1 Hz (a reading once a second) so the data comes in pretty regularly. At AlpineReplay, we do a few more checks to make sure we think the speed is accurate (what's the implied acceleration, how smooth is the curve, is there a jump in data points, etc.) We throw out all data points that seem fishy. We've spent a lot of time making sure our results are accurate, because our users love the leaderboard, and bad data ruins a leaderboard (as we learned early on before we made accuracy a focus).

So back to the original question: how fast are you going while carving? Most regular skiers are going beween 30-45mph. That's what we call you're max "sustained speed." But people almost always go faster than they think they are. There are people on the leaderboard who have gunned it and are approaching 80mph (but they're clearly not carving when you look at their path on a map). My roommate in college was a sponsored racer, and he was clocked in the mid 80s in a race (I think it was super G, but to be honest I'm not sure).

I'd love to answer any other questions you guys may have. Feel free to contact me directly at david@alpinereplay.com. Our CEO and my co-founder was the CTO of Magellan Navigation for more than a decade, so we know a lot about sensors and GPS. Can't wait to see you all on AlpineReplay!

[piusthedrcarve]

Hi All,

My name is David and I'm one of the founders of AlpineReplay. We've been getting a lot of traffic from Bomberonline, and I thought I'd stop by, say hello, and answer a few questions.

Welcome and thank you for doing this. So here is my question. How long would iPhone 4's battery last (assuming it was full with wi-fi off) if AlpineReplay is turned on?