Author Topic: To go True or Magnetic  (Read 5647 times)

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Offline ValentineWeather

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Re: To go True or Magnetic
« Reply #25 on: November 03, 2015, 12:44:53 PM »
Well figured out why the station we moved yesterday anemometer wind direction was so far off. The phone app was off by 30+ degrees compared to real compass. Did several more calibrations with app twirling phone and it finally started agreeing with compass. Don't trust these apps on phones I guess. :sad: The reason I used it in first place, it had declination built-in when the gps is turned on.
Randy, the Aviator is my father in 1963 with his Indian bike

Offline CW2274

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Re: To go True or Magnetic
« Reply #26 on: November 03, 2015, 01:21:18 PM »
Well figured out why the station we moved yesterday anemometer wind direction was so far off. The phone app was off by 30+ degrees compared to real compass. Did several more calibrations with app twirling phone and it finally started agreeing with compass. Don't trust these apps on phones I guess. :sad: The reason I used it in first place, it had declination built-in when the gps is turned on.
Does that mean you're coming to the dark side and going magnetic? :twisted:
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Offline ValentineWeather

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Re: To go True or Magnetic
« Reply #27 on: November 03, 2015, 03:36:55 PM »

Does that mean you're coming to the dark side and going magnetic? :twisted:

No  :-)
Randy, the Aviator is my father in 1963 with his Indian bike

Offline CW2274

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Re: To go True or Magnetic
« Reply #28 on: November 03, 2015, 05:00:40 PM »

Does that mean you're coming to the dark side and going magnetic? :twisted:

No  :-)
Darth will not be happy. :twisted:         






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Offline Old Tele man

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Re: To go True or Magnetic
« Reply #29 on: November 03, 2015, 05:18:30 PM »
My 4-Bears (Weather Rock) corollary:

FUNCTIONALLY, this is *how* I determine(d) "true" north for my VP2:

1) SPRING EQUINOX - at exactly NOON, placed a rock on the ground at the TOP (end) of the shadow from the pole.
2) SUMMER SOLSTICE - at exactly NOON, placed a rock on the ground at the TOP (end) of the shadow from the pole.
3) AUTUMNAL EQUINOX - at exactly NOON, placed a rock on the ground at the TOP (end) of the shadow from the pole.
4) WINTER SOLSTICE - at exactly NOON, placed a rock on the ground at the TOP (end) of the shadow from the pole.

The "straight Line" formed by the four three(*) rock locations "points" exactly NORTH(were the moss grows) - SOUTH(where the sun shines).

Done four years ago, I "check" things every three months: "Is the shadow on rock? Yep; all's OK!" (wink,wink).



(*) the two equinox rock locations coincide midway (the equinoxes) between the two solstice extremes
« Last Edit: April 17, 2016, 08:42:22 PM by Old Tele man »
SYS: Davis VP2/WL-IP & Envoy8X/WL-USB
CWOP: DW6988 - 2 miles NNE of Cortaro, AZ
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Offline CW2274

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Re: To go True or Magnetic
« Reply #30 on: November 03, 2015, 05:25:48 PM »
The 4-Bears (weather Rock) corollary:

FUNCTIONALLY, this is *how* I determine(d) "true" north for my VP2:

1) SPRING EQUINOX - at exactly NOON, placed a rock on the ground at the TOP (end) of the shadow from the pole.
2) SUMMER SOLSTICE - at exactly NOON, placed a rock on the ground at the TOP (end) of the shadow from the pole.
3) AUTUMANL EQUINOX - at exactly NOON, placed a rock on the ground at the TOP (end) of the shadow from the pole.
4) WINTER SOLSTICE - at exactly NOON, placed a rock on the ground at the TOP (end) of the shadow from the pole.

The "straight Line" formed by the four rock locations "points" exactly NORTH - SOUTH.

Done four years ago, I "check" things every three months: "...shadow on rock? Yep...all's OK!" (wink,wink).
Ya but, that takes a whole year. Ain't gettin' no younger! :-|
Davis Wireless VP2 SHT31 24hr 67CFM FARS
RW Tipper w/ CoCoRaHS

Offline RPinCA

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Re: To go True or Magnetic
« Reply #31 on: January 18, 2016, 03:25:46 PM »
@CW2274, from another discussion I know you were with ATC, and you know I'm a GA pilot. We know that ATIS broadcasts surface winds using magnetic direction, as it corresponds to magnetic runway headings. Winds aloft are reported in geographic (true/celestial) units. I've seen conflicting information on the net regarding what we should use in a PWS. On my own, macht nichts, I'll know what I chose. But when I hook up to Wunderground (et al), I presume they would want all reporting stations in correspondence. Where I live, magnetic variation is 13.75, so the question seems relevant.

I know you chose magnetic, and I suspect your ATC background played a role in this. I tried finding the answer at Wunderground, but couldn't. Correction... I just found the answer, but I'll finish this post. I used a feature of Google search I've found helpful. My query was

wind direction magnetic or true/site=wunderground.com

The "site=xyz.com" makes a big difference in search results. I thought you might find this interesting, and hope you'll take it in a positive spirit. This is the link for the answer: http://help.wunderground.com/knowledgebase/articles/129054-how-is-wind-direction-referenced

"Wind direction is referenced to true north, not magnetic. The wind display has a marker located at the wind source, with a small arrow indicating the flow of the wind."

So, in the process of asking the question, I found the answer that seems important to this community. Whether or not you'll choose to leave the dark side is an open question.  ;)

Offline CW2274

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Re: To go True or Magnetic
« Reply #32 on: January 18, 2016, 05:46:14 PM »
@CW2274, from another discussion I know you were with ATC, and you know I'm a GA pilot. We know that ATIS broadcasts surface winds using magnetic direction, as it corresponds to magnetic runway headings. Winds aloft are reported in geographic (true/celestial) units. I've seen conflicting information on the net regarding what we should use in a PWS. On my own, macht nichts, I'll know what I chose. But when I hook up to Wunderground (et al), I presume they would want all reporting stations in correspondence. Where I live, magnetic variation is 13.75, so the question seems relevant.

I know you chose magnetic, and I suspect your ATC background played a role in this. I tried finding the answer at Wunderground, but couldn't. Correction... I just found the answer, but I'll finish this post. I used a feature of Google search I've found helpful. My query was

wind direction magnetic or true/site=wunderground.com

The "site=xyz.com" makes a big difference in search results. I thought you might find this interesting, and hope you'll take it in a positive spirit. This is the link for the answer: http://help.wunderground.com/knowledgebase/articles/129054-how-is-wind-direction-referenced

"Wind direction is referenced to true north, not magnetic. The wind display has a marker located at the wind source, with a small arrow indicating the flow of the wind."

So, in the process of asking the question, I found the answer that seems important to this community. Whether or not you'll choose to leave the dark side is an open question.  ;)
I find it somewhat laughable that WU says magnetic is not even a viable choice, but for their purposes, I guess not. Yes, I've chosen magnetic for my personal use, but 99% of the public uses true. Another thing, the arrow in the example is pointing the wrong way as the point should face where the wind is coming from, not going to. I noticed that my local TV station now does it backwards too.
I'll stick with magnetic as I like to compare with the neighboring airports, dark side and all. ;)
Davis Wireless VP2 SHT31 24hr 67CFM FARS
RW Tipper w/ CoCoRaHS

Offline RPinCA

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Re: To go True or Magnetic
« Reply #33 on: January 18, 2016, 06:03:11 PM »
Quote
Another thing, the arrow in the example is pointing the wrong way as the point should face where the wind is coming from, not going to.

I noticed this trend in display style, as well. I think you and I are "old school" and understand it points opposite of the way the wind is going (rewording intentional). I remember needing to learn this characteristic as a young man.

It appears we are entering a Least Common Denominator world, where it's simply easier to reach the broader public than it is to train the broader public. Intellectual "Collateral Damage" of the Internet Age. The practice is spreading, as you noticed. Even the Wunder Weather Station has an internal display screen that mimics the Wunderground style gauge, and it is a solid, well-designed product. The reasoning behind the WWS decision is sensible; the reasons behind the reasoning are not.

I'll admit with some chagrin, this subject had me imagining ways to make a mechanical wind vane that points with the wind. I think it is do-able, although I've not yet made a prototype. My guess is the traditional pointer is a historical consequence from the days of bows and arrows.

Offline CW2274

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Re: To go True or Magnetic
« Reply #34 on: January 18, 2016, 06:05:20 PM »
Quote
Another thing, the arrow in the example is pointing the wrong way as the point should face where the wind is coming from, not going to.

I noticed this trend in display style, as well. I think you and I are "old school" and understand it points opposite of the way the wind is going (rewording intentional). I remember needing to learn this characteristic as a young man.

It appears we are entering a Least Common Denominator world, where it's simply easier to reach the broader public than it is to train the broader public. Intellectual "Collateral Damage" of the Internet Age. The practice is spreading, as you noticed. Even the Wunder Weather Station has an internal display screen that mimics the Wunderground style gauge, and it is a solid, well-designed product. The reasoning behind the WWS decision is sensible; the reasons behind the reasoning are not.

I'll admit with some chagrin, this subject had me imagining ways to make a mechanical wind vane that points with the wind. I think it is do-able, although I've not yet made a prototype. My guess is the traditional pointer is a historical consequence from the days of bows and arrows.
Well put.
Davis Wireless VP2 SHT31 24hr 67CFM FARS
RW Tipper w/ CoCoRaHS