 | | OT: Math Help
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| Figured I'd bounce this problem off the smart people in RTLTotonto...This was posted on an automation mailing list, with little resolution: I have a weather station which measures both the direction and speed of the wind and is connected to a PC to (...) (19 years ago, 5-Aug-05, to lugnet.org.ca.rtltoronto)
| | | | | Re: OT: Math Help
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| (...) I think using vector math (as you do above) is the right way to go. As for the special cases, meh, deal with it :) (19 years ago, 5-Aug-05, to lugnet.org.ca.rtltoronto)
| | | | | Re: OT: Math Help
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| (...) Here a detailed explanation I found puttering with google. I can't remember how to solve these equations anymore. So have fun. :-) (URL) (19 years ago, 5-Aug-05, to lugnet.org.ca.rtltoronto)
| | | | | Re: OT: Math Help
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| (...) If I remember right, the way we resolved this for real-world surveying problems and the like was to convert the degrees 180 < x < 360 into negative values relative to 0/north. 350 is -10, 270 is -90, etc. If x1 > 180 then x2 = 360 - x1 This (...) (19 years ago, 5-Aug-05, to lugnet.org.ca.rtltoronto)
| | | | | Re: OT: Math Help
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| (...) Don't you get the same problem at 180, now? 170 + 190 = 170 +(-170) = 0 I think there are several readings that can give you more than one result. For example, if you take two readings of 90 and 270, what should the answer be? 0? 180? never (...) (19 years ago, 5-Aug-05, to lugnet.org.ca.rtltoronto)
| | | | | Re: OT: Math Help
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| (...) And if you stop and think about it for a second or two, you'll realize your special case really does deserve special consideration. The average is no wind at all, so the direction would be undefined. (19 years ago, 5-Aug-05, to lugnet.org.ca.rtltoronto)
| | | | | Re: OT: Math Help
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| (...) One of the things I did pickup from "my" answer is you need to have a sample frequency small enough that you are not going to get wind direction changes of 180 degrees or more. And I say or more, because it's important to the average which (...) (19 years ago, 5-Aug-05, to lugnet.org.ca.rtltoronto)
| | | | | Re: OT: Math Help
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| (...) I noticed that, also. I think it says "changes must be less than 180". However, I'm not sure it matters which direction you went. For example, if you get readings of 10 deg and 20 deg, but in the time between the direction was never 15 (...) (19 years ago, 5-Aug-05, to lugnet.org.ca.rtltoronto)
| | | | | Re: OT: Math Help
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| (...) Oops, there was a mistake in my first equation above that I've corrected here, in order to give a negative number. (...) That's why I have " > 180", not "> or equal to 180" ;) Since the question was framed in relation to 0, that's what my (...) (19 years ago, 5-Aug-05, to lugnet.org.ca.rtltoronto)
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