h a l f b a k e r yI CAN HAZ CROISSANTZ?
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Ever wonder how fast you just tore down that slope? Want to compete with your favorite super G athlete?
Using optical mouse technology, you could mount an LED and an optical sensor to the underside of a ski or snowboard to measure the speed you are travelling over the snow. A numerical LED readout
could be mounted to the top of the ski or projected in a heads-up display in your goggles for easy reading.
the device could also store your max speed, average speed and total distance travelled (so you could know just how much skiing you're getting in for that incredibly expensive lift ticket).
Ski Speedometer
http://www.hammache...m/publish/72784.asp
(new) [Shz, Jan 08 2006]
[link]
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How are you going to measure the passing of snow? An optical mouse relies on a calibrated mousepad. I want this feature (in-goggle please), just not sure how it works. |
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back to the wheel/ball-mouse drawing-board/slope. I like this unless you are taking the piste +1 |
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Optical mice have very high-resolution cameras, and one of these cameras would probably be able to detect the change in snowflake patterns. Mine detects change on my apparently flat-brown desktop, which seems to have no change at all across it to my eyes. |
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Since my mouse will work on carpet, it seems plausible that the optical mouse type arrangement could work if was able to look through a clear "window" that would be on the same plane as the contact surface of the ski/board so as to prevent it being packed with snow/ice. The window would have to be a fairly tough material to resist scratching (assuming that the surface of skis get scratched in use). |
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I've got a cheapie optical mouse with a busted button that you can have. |
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Obvious name: Skeedometer. |
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Yes, desktop surface granularity is measurable. Question clarification: How do you calibrate snow? (genuine curiosity – I don’t know how) |
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//How do you calibrate snow? //
An excellent question. The quality of snow on a ski slope changes noticeably as you change altitude, which might affect the sensor's abilities. (WTAGIPBAN) |
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I don't see why any calibration would be necessary, but focus and wax might be problems. Rather than looking down at the snow it might make more sense to look sideways, maybe from your boot, and just watch how fast nearby scenery goes by. |
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On-board radar instead of optical mouse technology? That could work. |
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To work as a speedometer, the system would need to take a high resolution snapshot of the passing ground and compare it to another high resolution snapshot from just a moment before. Using 2D correlation techniques, an onboard processor would identify the same spot in each image and calculate the distance moved. The time elapsed between frames is known, so the speed can be calculated easily. |
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It is important to get a large enough viewing area and fast enough frame rate to register the same spot in two successive frames with enough context to positively identify it as the same spot. |
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Computation need not happen at the frame rate, however. A memory buffer could store a burst of two or three frames taken at an extremely fast frame rate. A relatively slow computation could then return the speed result as much as a half second later. When the computation finishes, a new burst of frames is captured, and the process repeats. A skier wouldn't be accelerating enough to need updates more often than that, except during hard stops and sharp turns (when the skier wouldn't be watching the speedo anyway). |
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By the way, would the inclusion of a speedometer be more likely to encourage safer speeds (sign: speed limit 12) or to encourage reckless skiing in an attempt to go faster than everyone else? ("Dude, I just topped 23!") |
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I wonder if ski racers would have a use for such a device as a training aid? |
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GPS could just about manage this, I guess. Or a pito tube fed to a digital arirspeed indicator, but you'd have to make sure that the pitot always pointed into the airflow to get an accurate reading. |
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Ground sensing would be tricky but might be possible. The problem is that if you have a window in the base of the ski/snowboard it's going to abrade and be obscured pretty fast. |
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The best thing might be radio beacons at fixed points down the piste, and triangulate of those. |
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I second the triangulation method...if you measure movement past the snow by comparing images, you'd have to take into account the movement of the snow away from the ski, which varies with conditions, speed, and downhill direction. |
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Thanks for all the feedback. I tried to find out some more information about optical mouse technology, one source said the max speed they can detect is 40 in/s, less than 3 mph. But the mouse is optimized for small movements with large accelerations, so following bigbrother's idea of just taking a few frames in a burst could give much better performance. |
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I was thinking about hacking my old optical mouse to put together a simple mock-up. Anyone know where I can get info about the USB protocol or optical mouse circuit diagrams? |
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Just checked - my optical mouse (one of those fancy Apple ones) works on my matt-black mousepad, in the dark, so it should work on snow (wait! - hang on! My garden's full of snow! Why don't I just lug the iMac out into the garden and see if it... oh never mind).
A nice side-effect of this idea is that when skiing in the dark, the red glow leaking from the LEDs on the underside of your skis would look cool.
Croissant. |
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Which reminds me of another idea I had -- Ground effect kit for snowboards. Embed some cold cathode tubes or leds in the underside of snowboards to give a cool effect when they go off jumps. |
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Actually why not have all aftermarket car products for snowbooards/skis: spoilers, decals, etc :) |
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maybe a heads-up display on the goggles with speed, time of current run, etc. I have a watch that measures vertical speed by air pressure - maybe integrate this with a known slope - well, a slope with a known slope - to calibrate. |
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LEDs on the bottom - powered by piezoelectric movement. And maybe a body kit with spoiler too. I'd buy it... |
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Optical mice don't need a calibrated mouse pad to work, I use mine on some regular old mouse pad and it works fine. To solve the problem of abrasion, you can have the sensor mounted to the back of the ski, slightly elevated off the surface of the snow (1/4 inch should do fine). The REAL problem that occurs is that snow reflects light, and that can be a problem when the camera tries to capture an image. |
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Just carry a GPS in a pocket on your arm or your hat(for good reception). Mine gives current speed and max speed. Some GPS's have Buetooth interface, so you just need the Bluetooth HUD glasses that must have been baked somewhere... |
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Doesn't work if you ski through a tunnel though, or perhaps in really dense forest, but if the trees are that close, you should probably be looking out for them, not at your GPS... |
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I swear I have seen this baked before. However, I am unable to find a link, so good for you. :-) |
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The device im thinking of used a remote sensor that had a little paddlewheel type of thing on it, like some boats use. I believe it was integrated into the board, placed centerline. Probably spring loaded to maintain contact with the snow. |
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Personally, I use a GPS like [jwt] mentioned. It usually works ok. I don't often look at it when im riding though. Just bomb down a hill and check the max speed at the bottom. [off topic] It also helped me find a glove I had dropped on the lift one time. I went back up the lift and when i spotted the glove below, I marked the point as I passed. Next run down I simply navigated to the waypoint. Worked like a charm... [/off topic] |
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Initially I liked the idea, then someone mentioned speed limits :( |
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I use GPS too, got 68mph once..... I don't know where they hide them but downhill skiiers must have balls the size of watermellons with the speed they go, even more scary is the speed skiiers, 155.834 mph... when I was going 68 it felt really fast just think of going 155. |
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GPS might be a little shaky on a steep mountain because it extrapolates speed from lattitude and longitude. Radio triangulation would work better because you could set the whole thing up parallel to the ground. |
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GPS for the fix at the start of the run and accelerometers to calculate the delta. Probably could do away with the GPS because an absolute position isn't that important. It's all relative. |
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Good solution, no need for the gps at all accelerometers can give you all the information you need, recalibrate them when you stop to get on the next lift |
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I was interested in how the optical mice work, and found the following on Uncle Tom's hardware guide:
Best frame rate- 6000 per second.
Counts per inch- 400.
And from my own measurement:
Area of observation approx 2mm square.
If I assume that the imperfection in the field of view must re-appear again in a different place in the next frame in order to see the movement, then it must move a maximum of 2mm (probably less) in 1/6000 seconds.
This gives a maximum speed of 12 m/second or 43km/h.
I can also guess that the camera resolution is approx 31 pixels across.
[bristolz], three accelerometers would be able to tell you max cornering G as well, and allow re-plotting of the complete run in terms of direction & speed.
I think it's basically done for race cars, now, except for the z-axis. |
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I like the idea of being able to 3D model all the runs that you did that day in the evening, giving you a wire frame map of the areas of the mountain that you skied. |
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Could be a good source of information for the resort to put on ther website, 3D models of the mountain. You could even build in a route finder for the closest bar/restaurant/lift/friend (with wireless coms) |
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Great idea, but have you ever tried an optical mouse on a glossey white surface or glass? It doesn't work because of the way that the light is deflected.
A sonar sensor like used in fish finders ought to be less expensive that radar or gps and could work. I like many others use the GPS in pocket method now.. |
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Alternatively, for a slightly lower-tech solution, just have metal panels situated at the bottom of every run. Put a little radio transmitter on your hip or whatever, have it "ping" the panel...and then detect the range and velocity. |
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Some people call that RADAR, and it'd create a neat little series of cottage industries for sales and rentals of transmitter/receiver units, flat metal panels, and belts. |
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I know this is baked. I've seen little paddlewheel-type speedometers that clip to the back edge of the ski. However, I can't find a link. Therefore, neutral vote. |
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(+) So much more elegant / cheaper / self-contained than GPS. |
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But yes, the ice will scratch, and the snow will cover. I'm thinking the best place to mount this is on your back, pointing down & a bit behind you. Your derriere is not usually covered in snow like your boots are. |
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Whatever the solution, I think it should also include a sound system that would inform you of the current speed so that you wouldn't feel the need to look at the visor while skiing. It could also include some inteligence. For instance, if you were going too slow, it would say something like "Come on, sissy, go for it". |
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It could also have a memory of your previous speed records. If you achieved really high speeds it could say something like "I don't think your skilled enough for this speed, dude". It could also include an accelerometer. If it detected a very high deceleration it would say "Told you!...asshole". If this deceleration was extreme it would just call 911 or whatever works on those places. |
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I don't know if I like the idea of my skis swearing at me. After all, the ski patrol, girlfriend, instructors, and orthopaedic surgeons already call me dumbshit. |
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No HUD for me. I want my speed projected onto the snow in front of me in foot- high letters so that others can see how fast I'm going. It should also say "Bye Bye!" as I top 70mph. |
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An integral level within the ski could be used calculate the slope of the ski at any given time. Throw in an altimeter and stopwatch and you have everything you need to perform the calculations. The only drawback to this method I can see is the accuracy of the altimeter....I'd say +/- 3m would be sufficient. |
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Almost here! Not the same technology as described here, but still, a ski speedometer. It has a small radar unit that clips on your boot or straps to your leg and transmits readings to a display that can be worn as a watch (tells time too). I’ll post a link as soon as there is one to post. |
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Sorry to blow my own trumpet but have you seen www.skido.info? |
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It's lots and lots of fun! |
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would be hard to make it work, but not impossible, so croissant. :-) |
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