ATIS and METAR: true or magnetic?

Discussion in 'Flight Following' started by Eric Reyes, Mar 13, 2018.

  1. Eric Reyes

    Eric Reyes Filing Flight Plan

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    I was taught that if you read a wind direction in text form it will be based on true north, such as METARS, TAFS, and wind aloft forecasts
    and if it’s spoken, the wind direction will be based on magnetic such as ATIS, AWOS, ASOS.

    However I spent the last half hour listening via the ATC app to ATIS broadcasts at over a dozen different airports out West where they have magnetic variations between 10 to 12 degrees and then I compared their ATIS reported wind directions to their current METARS.

    I double checked the recorded ATIS times and the METAR times and in every case they were identical. What I found really surprised me. At every one of the more than dozen airports that I checked the reported ATIS wind direction was the exact same as their METAR reported wind direction. I checked small, medium, and large airports, some with human recorded ATIS and some with a computer generated voice.

    I have been studying for my check ride oral exam and I read that text written winds are true and spoken winds are magnetic but now I am thoroughly confused. This whole thing started when I noticed my home airport ATIS and METAR always had the exact same wind direction even though the airport is has a -6 magnetic variation. At first I figured one of two things could he going on.

    A. The ATC guys at my home airport who are recording the ATIS are not following regulations and they are reporting the ATIS winds in true north.

    Or

    B. Because the magnetic variation is only 6 degrees, and the ATIS and METAR wind are rounded to the nearest 10 knots, the magnetic variation is being rounded away.

    So that’s what prompted me to check a bunch of airports out West where they have magnetic variations between 10 to 12 degrees W.

    So why is every single one of these airports that I checked reporting the exact same wind direction on their ATIS and their METAR?

    One other possibility I thought of was perhaps ForeFlight was converting the true north METARS to magnetic north, but I also checked the METARS on AviationWeather.gov and they also had the same exact wind direction as the ATIS for all of the more than one dozen airports that I checked. Keep in mind that all of these airports are located in areas with magnetic variations between 10 to 12 degrees.

    So why is their Metar wind and ATIS wind direction the exact same?

    And since they are the exact same and what we were taught doesn’t seem to be accurate anymore, so are they both reporting in magnetic or are they both in true north?

    What about TAFS and winds aloft? Are they still based on on true direction?
     
  2. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    Where are you getting the ATIS broadcasts? I wasn't aware LiveATC or anyone else carried them.

    But yes, METAR and winds aloft are still true and ATIS/AWOS is still reported as magnetic.

    If we are talking METAR vs AWOS, remember that AWOS is current; METAR can be an hour old, and a fairly large shift in wind is needed to trigger a SPECI.
     
    Last edited: Mar 13, 2018
  3. JohnAJohnson

    JohnAJohnson Cleared for Takeoff

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    If it's written, it must be true.
     
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  4. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    Especially if it's on the Internet!
     
  5. denverpilot

    denverpilot Tied Down PoA Supporter

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    What if you read the ATIS via Digital ATIS request on the screen of your FMS in your Gulfstream? :)
     
  6. ejensen

    ejensen Pattern Altitude Gone West

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    I get in on my MFD through XM for a bit less
     
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  7. ejensen

    ejensen Pattern Altitude Gone West

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    Is this still good (almost said true)?

    The general rule is:

    If you read it, it's true. If you hear it, it's magnetic.

    All charts and textual sources (METAR, TAF, winds aloft, surface analysis charts, etc) use true north as the reference.

    ATIS/AWOS/ASOS broadcasts, or any information a controller gives you over the radio, is magnetic.

    Wind direction broadcast over FAA radios is in reference to magnetic north.

    AIM Section 7-1-11 (page 7-1-26 in the 5/26/16 edition)

    One exception to the "if you hear it" rule is that a FSS briefer will read you the winds referenced to true north, since they're just reading you the charts/textual information.
     
  8. Timbeck2

    Timbeck2 Final Approach

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    The ATIS we broadcast is directly from the METAR, as a matter of fact, the computer voice is quoting the METAR exactly. So I don't get the notion how one is magnetic and one is true.
     
  9. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    Interesting. I thought "ATIS weather information comes from a variety of sources depending on the particular airport and the equipment installed there. The reported weather may come from a manual weather observer, weather instruments located in the tower, or from automated weather stations." (Source: IPH)
     
  10. denverpilot

    denverpilot Tied Down PoA Supporter

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    I think the world has started to mix these a bit. Thus my joking comment about D-ATIS vs say, a digitally received METAR via ADS-B IN. In theory those should be different.

    And then there’s the digitalker ATIS that seem to be just reading the METAR.

    And of course PIREPS are “long form and being read from paper” but are always in magnetic.

    There’s a lot of exceptions to the read it/hear it rule.

    All I know is, I hear the ATIS and the METAR usually matches at my airport. Don’t think they’re supposed to, but they do. :)
     
    Last edited: Mar 14, 2018
  11. Timbeck2

    Timbeck2 Final Approach

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    Never in my 26 year career as an air traffic controller have I had to convert true or magnetic wind information for the ATIS and I've used at least 4 different types of ATIS recording/broadcasting equipment. It has always been broadcast exactly as the observation, automated report or METAR depicted it.
     
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  12. Timbeck2

    Timbeck2 Final Approach

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    It doesn't matter if it is spoken or read. Terminal wind information such as that on an ATIS are always magnetic. Winds aloft or otherwise "flying around" wind is true.
     
  13. dmspilot

    dmspilot En-Route

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    You just said you read it directly from the METAR so which is it?
     
  14. denverpilot

    denverpilot Tied Down PoA Supporter

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    Not PIREPs. :) Pilot gives them in magnetic if needed... or they're reporting off of a VOR radial, that's magnetic too... and they get reported in magnetic, from whence they came... :) :) :)
     
  15. mscard88

    mscard88 Touchdown! Greaser!

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  16. Unit74

    Unit74 Final Approach

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    What value does true have in ATIS/AWOS anyway? Everything we are using in the cockpit is magnetic. That makes about as much sense as quoting your altitude in kilometers or your speed in feet per second. Completely worthless information to the flight.
     
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  17. denverpilot

    denverpilot Tied Down PoA Supporter

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    ATIS is not in true. It’s read off of the supposedly-calibrated-to-magnetic wind instruments in the tower cab.

    AWOS is similarly adjusted, it has a calibration setting for magnetic when you install the device.

    $20 says nobody’s ever seen the installers back on site to adjust either one for more than the number of years that would change the magnetic stuff though. Probably only get reset when something breaks in the “reinstall anemometer that blew itself into little pieces” checklist.

    And good luck finding a METAR that doesn’t match the ATIS, which means the “read it vs hear it” teaching method is completely blown. :) But one can start there and then explain the exceptions.

    Unexplained/undocumented exceptions. :)
     
  18. Unit74

    Unit74 Final Approach

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    i know... Thats what I'm saying. True is really irrelevant in the cockpit.

     
  19. Timbeck2

    Timbeck2 Final Approach

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    I don't understand your question, which is what?
     
  20. dmspilot

    dmspilot En-Route

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    In one post you stated the the wind for ATIS is read directly from the METAR, in another you said the ATIS is always magnetic. Since the METAR is referenced to true north, both of your statements cannot be true.
     
  21. Timbeck2

    Timbeck2 Final Approach

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    I never said the METAR is referenced to true North. That is what is not true.

    I'll rephrase. Both of my statements are true. METARS are not referenced to true North.
     
  22. dmspilot

    dmspilot En-Route

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    I didn't say that you did. But it is.
     
  23. Timbeck2

    Timbeck2 Final Approach

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    Well you better tell every weather person I've worked with in the past two decades because they say it isn't.
     
  24. dmspilot

    dmspilot En-Route

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    Since I don't know who these people are, maybe you should tell them yourself?

    Screen Shot 2018-03-16 at 10.54.35 AM.png
     
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  25. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    This is from AC150/5220, "AWOS for Non-Federal Applications." That's the AC which discusses, among other things, the requirement for AWOS system connected to the federal dissemination. Most METAR come from these.

    Aviation Routine Weather Report Format (METAR). Coding of the AWOS output must meet the METAR message requirements defined in the latest edition of the Federal Meteorological Handbook No. 1 (FMH-1). National network distribution of wind direction must be in True while local dissemination, e.g., radio and telephone, must be Magnetic.​
     
  26. Timbeck2

    Timbeck2 Final Approach

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    Look fellas, I got no dog in this fight. If you want to argue in order to be right about something it isn't going to be with me. I saw this thread, really didn't know the answer myself and picked up the phone and asked my friend Matt Lawrance who is a retired forecaster now working as a civilian in our weather shop. What I stated above in reference to the wind and "flying around wind" came directly from him. It doesn't make any sense for the METAR to mean one thing when you read it and another when you speak or broadcast it. The METAR for us and every other ATC facility I know of is automated and the ATIS is recorded and broadcast exactly as read. Why would anyone in aviation want a weather product with wind speed and direction in reference to anything other than in relation to the magnetic oriented runway?

    Mark's quote above explains a lot in: "National network distribution of wind direction must be in True while local dissemination, e.g., radio and telephone, must be Magnetic."

    ATC doesn't broadcast in National distribution, ATC broadcasts local (and why wouldn't they?) so that perhaps may be where this disagreement/confusion is coming from.
     
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  27. mscard88

    mscard88 Touchdown! Greaser!

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    I would have said I just wing it Tim. ;):)
     
  28. dmspilot

    dmspilot En-Route

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    This isn't Who Wants To Be A Millionaire. If you think your "Phone a Friend" is a better source than AC 00-45H, Aviation Weather Services, which is the authoritative reference material on the topic which comes directly from the FAA, I can't help you.

    I don't know, but every product described in AC 00-45H, Aviation Weather Services, uses true north. I suppose there is a reason but I am not going to speculate on what it is.
     
    Last edited: Mar 16, 2018
  29. MikeELP

    MikeELP Pattern Altitude

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    Current KELP METAR shows wind 320. ATIS says 310. METAR true, ATIS magnetic.
     
  30. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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  31. denverpilot

    denverpilot Tied Down PoA Supporter

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    Now I want to call the ASOS phone number at some place that reports METARs. I don’t think I’ve ever heard a difference between what was read. :)
     
  32. injb

    injb Pre-takeoff checklist

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    Wouldn't you want this when you're planning a flight with a chart? The chart is base on true directions. You have to adjust your final course calculation for magnetic deviation anyway, so the simplest approach is to have the wind as a true direction.
     
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  33. jimhorner

    jimhorner Line Up and Wait

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    Planning a flight with a chart? You mean a paper chart? Something that unfolds? Is that possible? How is this done? Say more...




    I kid, of course, but it is interesting how technology has changed things. My Garmin Pilot app on the ipad takes all that into account, and my autopilot does a great job of following the magenta line correcting for the actual winds as necessary. Several years ago, I flew from CA to TN to visit my family, and my dad and I got into a discussion about flight planning. He’s even more of a curmudgeon than I am, and he kept saying how much better the paper charts are than the ipad. “Fine, Dad” sez I, “let’s have a race. We’ll both plan my flight back to CA. I’ll use my ipad, and you use the paper charts. Ready? Go. ... I’m done.”

    When I got back into flying a few years ago from a 23 year hiatus, it was amazing to me how things have changed. I haven’t touched a plotter in a long time.


    Sent from my iPad using Tapatalk
     
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  34. Eric Reyes

    Eric Reyes Filing Flight Plan

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    For all of you who repeated “if you read it it’s true and if you hear it it’s magnetic” you are missing my point.

    As I stated before I checked over a dozen airports out West where they have very large magnetic variations +10 degrees or more and at every airport the reported written METAR wind direction was the exact same as the ATIS or ASOS wind direction being reported verbally via the Live ATC app.

    So either both the METAR and ATIS/ASOS are being repeated in true or they are both being reported in magnetic, but I can tell you without a doubt that they are being reported the exact same even at airports with +10 or more magnetic variations. You can quote all the regulations you want and you repeat the “read it it’s true and hear it it’s magnetic” statement, but it does not change the fact that in reality METARS and ATIS wind directions are being reported the exact same regardless of the amount of magnetic variation.

    By all means check for yourselves. Use ForeFlight or Garmin Pilot or whatever source you want to check some airport METARS and then use the Live ATC app to listen to their ATIS. Actually I recommend starting with the Live ATC app because not every airport is available in Live ATC and some airports that are available do not have an ATIS frequency available in the app. Be sure to select some airports far out West where they have magnetic variations +10 or greater.

    I will add some of the airports that I checked. I don’t them all but I will do the exercise again and add the names as I locate them again.

    Airports with sans METAR and ATIS wind direction:

    KSDL Mag Var 10E
     
    Last edited: Apr 10, 2018
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  35. John Myers

    John Myers Pre-takeoff checklist

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    I know this is an old thread, but I found it interesting and wanted to add my limited insight. ACs are written by people, and they are sometimes wrong or outdated. Sometimes regs are not followed, sometimes the charts are not updated with a new tree.

    Point being trust and use the official docs and regs because they are usually correct and useful, and be aware on occasion they aren’t and don’t turn our brains off when something seems wrong. The FAA website accepts error reports.
     
  36. Lindberg

    Lindberg En-Route

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    I don't know about y'all, but I've never converted from true to magnetic when calculating a crosswind, even though runways are numbered magnetic. So surface winds must be magnetic. And every flight planning form I've seen puts the conversion from TH to MH after calculation of wind correction. So winds aloft must be true. QED.
     
  37. dmspilot

    dmspilot En-Route

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    Reporting an error in the AC to the FAA would not be appropriate, as there is no error. All sources at the FAA, NWS, and ICAO agree that METARs are to contain wind direction measured with respect to TRUE north. Some people choose not to believe cold hard facts and would rather listen to what their cousin's friend's Aunt's ex-husband thinks instead. There are also people who believe the Earth is flat, so what can you do.
     
  38. sourdough44

    sourdough44 Pattern Altitude

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    7EA98964-85CC-41C7-97C5-CFA356E7387A.jpeg Just keep your flights up & down the MS River, then it will be of no concern.
     
  39. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    The rate of change of magnetic declination has been speeding up. More up-to-date data can be found on sectional charts.