Ballistic AE Question

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by scsims, Feb 27, 2013.

  1. scsims

    scsims Well-Known Member

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    Should I have "Absolute" pressure on or off, if I'm just using the updated weather information that the software provides?

    I can't seem to find this answer anywhere.
     
  2. cwinner

    cwinner Well-Known Member

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    If your using a local weather station then leave it off.........
     

  3. scsims

    scsims Well-Known Member

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    So absolute is for if you have a portable weather station device??
     
  4. BrentM

    BrentM Well-Known Member

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    I might be wrong but I don't think you can get absolute on the net. I can't find it here locally. I do get absolute with my kestrel or Leica. Generally I just use this number on the mountain as it is simply 1 number to input and I am done.

    To answer part of your question, if you are using the weather station info you don't need the absolute. It will give you the elevation and corrected presure. IMO they give the same results so use the one most handy to you.
     
  5. scsims

    scsims Well-Known Member

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    I emailed the developer of software and below is their response. Not quite sure if he answered my question or not.

    "When absolute is on, it won't adjust for sea level pressure input. With off it will assume the value is sea level. I've found some weather servers return un-adjusted pressure, while others return sea level pressure. If you think the data you're getting in your region is sea level then you want to turn that switch off and let ballistic adjust to your current altitude. This may be the default in the future. What the weather services advertise they send and what actually gets sent appear to be inconsistent. "

    Pardon teh spellnig; Sent form my iPhone

    On Feb 28, 2013, at 1:36 PM,

    I wrote,

    I don't have a portable weather device that provides any data other than wind. So I've been using the update button in the top right corner of the HUD settings screen to get this information. When I do this the "Absolute" setting automatically turns on. I was under the impression that I shouldn't be using absolute pressure unless I had a portable unit that could read pressure at my altitude. Should I toggle this back off in this situation?

    Thanks,
    Scott
     
  6. jlamb

    jlamb Well-Known Member

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    Interesting. I shoot at 5800 feet. I'll turn it on and calibrate and let you know what I find out.
     
  7. BrentM

    BrentM Well-Known Member

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    Well that was kinda not all that helpful. Ha ha. What is the baro value you are getting from the local? For example here Bp at 2800 ft might be 30.31. Abp will be around 27.50.
     
  8. cwinner

    cwinner Well-Known Member

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    Yes, the response you got was a round about way of saying that most weather stations and pressure reports are adjusted for sea level based upon the altitude.......it's a way to report consistent readings across a statewide or regional area. Attitude and pressure are directly related and the higher the altitude the lower the pressure....take a state line NM with elevations ranging from 3,000 to over 13,000 feet.....if pressures were not adjusted to sea level a pressure map would make it look there is a low pressure area over every mountain range.

    Check out this sticky thread for more details.

    http://www.longrangehunting.com/forums/f19/altitude-vs-barometric-pressure-11950/


    In short if you updating from the web absolute=off.....with a kestrel calibrated for zero elevation absolute= on.

    Hope this helps...........