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#1
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Ski Speedometer
OK all, here is the challenge, come up with a viable way of measuring
your speed on skis. I have heard tell of using GPS, but since it will only get your horizontal speed component, and not the verticla, it will always read low. What else can you think of? |
#2
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On 18 Jan 2006 02:51:50 -0800, "fat_boy" wrote:
OK all, here is the challenge, come up with a viable way of measuring your speed on skis. I have heard tell of using GPS, but since it will only get your horizontal speed component, and not the verticla, it will always read low. Not so. They work in 3D so will be accurate on a slope too. -- Ace (brucedotrogers a.t rochedotcom) Ski Club of Great Britain - http://www.skiclub.co.uk All opinions expressed are personal and in no way represent those of the Ski Club. |
#3
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How? If a GPS devices prime role is to give the lat and long, it will
give you your position in terms of a flat grid on the earths surface. For it to calculate speed, it measures the change in distance over time relative to that flat grid. So, unless the GPS unit ALSO measures altitude, and can add a vertical component to the calculation, it can not work for skiing. |
#4
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And not only that, because air is compressible its density with respect
to altitude is not constant, so the device would need calibrating (at set altitude) to get an accurate change in altitude. |
#5
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Altitude can be calculated with a GPS when it can see more than 3
satellites.. and it is not calculated using Barometric pressure.. "fat_boy" wrote in message oups.com... And not only that, because air is compressible its density with respect to altitude is not constant, so the device would need calibrating (at set altitude) to get an accurate change in altitude. |
#6
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fat_boy wrote:
How? If a GPS devices prime role is to give the lat and long, it will give you your position in terms of a flat grid on the earths surface. For it to calculate speed, it measures the change in distance over time relative to that flat grid. So, unless the GPS unit ALSO measures altitude they do |
#7
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On Wed, 18 Jan 2006 14:33:17 +0100, davidof
wrote: fat_boy wrote: How? If a GPS devices prime role is to give the lat and long, it will give you your position in terms of a flat grid on the earths surface. For it to calculate speed, it measures the change in distance over time relative to that flat grid. So, unless the GPS unit ALSO measures altitude they do And devices such as the Garmin Geko 300 also contain an altimeter to assist the accuracy problems with altitude detection. Also very portable. I am not sure how it would stand up to the cold. The batteries will certainly be rubbish in such temperatures. |
#8
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In message
Ian Blake NoNotMe@NotAnywhere wrote: On Wed, 18 Jan 2006 14:33:17 +0100, davidof wrote: fat_boy wrote: How? If a GPS devices prime role is to give the lat and long, it will give you your position in terms of a flat grid on the earths surface. For it to calculate speed, it measures the change in distance over time relative to that flat grid. So, unless the GPS unit ALSO measures altitude they do And devices such as the Garmin Geko 300 also contain an altimeter to assist the accuracy problems with altitude detection. Also very portable. I am not sure how it would stand up to the cold. The batteries will certainly be rubbish in such temperatures. No problem with the batteries. Skiing on piste last week in Les Arc I was using my Geko301 with 800mAh NiMh rechargeables. I had the device attached to my rucksack shoulder strap. Temperatures were about -4 to -10 during the week. One set of fully charged batteries would just about last from 9.30am until 4.30pm. In practice I took two sets of batteries out each day and changed them over mid-day and then recharged all four each evening. When ski-touring I tend not to have the device on all day but only intermittently to record major waypoints and features along the route. I also carry alkaline or lithium AAA instead of the NiMh cells. Under such circumstances I've usually found two sets of batteries enough for at least a weeks worth of touring data with capacity to spare in case I need to use the device for emergency navigation. Mike http://www.path.cam.ac.uk/~mrc7/hauteroute/ -- o/ \\ // |\ ,_ o Mike Clark \__,\\ // __o | \ / /\, "A mountain climbing, cycling, skiing, " || _`\,_ |__\ \ | immunology lecturer, antibody engineer and ` || (_)/ (_) | \corn computer user" |
#9
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"fat_boy" wrote in message oups.com... How? If a GPS devices prime role is to give the lat and long, it will give you your position in terms of a flat grid on the earths surface. For it to calculate speed, it measures the change in distance over time relative to that flat grid. So, unless the GPS unit ALSO measures altitude, and can add a vertical component to the calculation, it can not work for skiing. Considering the GPS system is primarily a military system used for aiming missiles I think that the altitude is probably an important part of the position! -- Paul Schofield |
#10
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Why?
Think of a flat, grid defined plane. If an object is programmed to get to xx,yy the satelite(s) can take care of that. Altitude is more easilly taken care of by an altimiter. |
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