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Thread: East Snowfields

  1. #11
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    Default Wind Chill

    Alright, now that's what I'm looking for. If I'm skiing directly into that wind I'm sure I'm not going anywhere near 40mph, am I? Hard to say. And the wind isn't blowing 40mph at ground level, either, is it? So, I'm probably not dealing with wind chills any worse than what is posted, unless I'm getting up good speed and heading straight into the wind. Correct?

    When I'm skiing straight into the wind it feels as though I'm barely moving. I'd say 20-25 tops. If the winds blowing 20-25 at ground level then I'm only talking 40-50mph airspeed. With a 5 degree airtemp then it's like -20-25 windchill.

    Am I in the right neighborhood?
    KDT

  2. #12
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    Quote Originally Posted by KD Talbot
    With a 5 degree airtemp then it's like -20-25 windchill.

    Am I in the right neighborhood?
    KDT
    Seems about right.
    Bill
    Next up: Vermont City Marathon: May, 2011
    EasternLight

  3. #13
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    Default

    Here is a wind chill formula I found online, hopefully this will help you.

    Wind chill temperature = 35.74 + 0.6215T - 35.75V (**0.16) + 0.4275TV(**0.16)

    T is the temp. in degrees F.
    V is wind speed in statute miles.

    Note: In the formula, ** means the following term is an exponent (i.e. 10**(0.5 ) means 10 to the 0.5 power, or the square root of V), - means to subtract, + means to add. A letter next to a number means to multiply that quantity represented by the letter by the number. The standard rules of algebra apply.
    Steve
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  4. #14
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    Cool most important thing with ski speed ......

    CUT YOUR SPEED BEFORE YOU JUMP!!!!!!!!!!!!!!!! (l.o.l.) Wind speed, ski speed and Temp is neat to figure out but what about speed, distance off ground when jumping and how much pressure is on the leg if you don't land it?? My son was at Stratton on Monday and he said temps were rather chilly willy there. Great idea to figure wind speed and speed skiing to actual temps that you are in on the mountain.

  5. #15
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    Default

    MWO's wind chill page, with handy chart, is at http://www.mountwashington.org/weather/wind-chill.php

  6. #16
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    Default

    Quote Originally Posted by Patrad Fischroy
    It is my impression that the GPS will underestimate your speed on the slope. I am pretty sure that it will only give you your horizontal velocity, not the velocity along the slope. And if it is calculating the distance along the slope the vertical measurements on the GPS are considerably less accurate than the horizontal ones. I seem to recall they are on the order of 3-5 times less accurate.
    I do not think it is a question of GPSs being inaccurate. They just record the location - and elevation. It is a question of what software does to calculate distance and speed off the data. If it assumes flat surface - roads - water - then it will not be accurate. However, if it uses elevation in the calculation, then it should be accurate.
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  7. #17
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    Accuracy using a GPS is a relative term. Here is some data that I have picked up over the years as a mapper and with some dabbling in survey work. You may feel that I am quibbling, but in the case of steep terrain the effects of this are somewhat more severe than on flat land.
    Most handheld consumer GPS units have an average accuracy of about 1-5m under optimal conditions, that is, clear sky, widespread satellite coverage, and minimal solar activity. The satellites used for our GPS system only extend to a latitude of 55 degrees North and South. When skiing, you are generally on a North facing slope. The chances of having a good constellation of satellites are not so good as most of the satellites will be blocked by the mountain. Plus, due to the geometry of the satellite, (their designed positioning was optimized for horizontal positioning) vertical measurements have an accuracy that is on the order of 1.5 to 2 times worse than the horizontal or 1.5-10m.

  8. #18
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    So...does anybody know about snow conditions on the East Snowfields?
    Bill
    Next up: Vermont City Marathon: May, 2011
    EasternLight

  9. #19
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    Default

    Sorry for the sidetrack

  10. #20
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    Quote Originally Posted by Bill O
    So...does anybody know about snow conditions on the East Snowfields?
    Looking at the zooms things seem to be filling in nicely. Certainly big improvements over last week in the east fields on in Tucks.

    As for GPS...the kind we have access to is not really to be used for elevation, unless it has a built in barometer. Unless you have more information than me, and you might, I think the GPS satellites go over 55 degrees in latitude. They are polar orbiting satellites, meaning they go over the poles, and complete an orbit every 90 minutes or so.

    They are great fun for measuring speed when sea kayaking, but probably not for skiing.
    Bill
    Next up: Vermont City Marathon: May, 2011
    EasternLight

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