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Thread: Variation and Deviation

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    Junior Member smoke's Avatar
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    Variation and Deviation

    Last night I was trying to navigate to a target 120 NMI away with only using the compass, no matter how many times I tried I could only get within 5 NMI.

    Does anyone know if DCS models Variation, Deviation and Wind Drift if so it would explain my multiple hours of suffering to no avail in the end? If not I apparently need to fly a straighter course.

  2. #2
    Member Ashy's Avatar
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    I would almost say that the main cause of that would be wind well and other factors. it is modeled. The main things are going to come in to play here. Wind blowing you off course added with gross weight of your plane constantly changing because of fuel consumption. There is calculations that can help with this all over the internet. A compass is all fine and dandy but with out a sectional chart and a stopwatch to actually have in hand its almost point less(if you were wanting to get that nitty and gritty with it). With the sectional chart you could also navigate visually. And if you could get all that then i would recommend going to your local airport and getting a flight computer to help with such.


    Just something i googled because i am not home to be able to find the calculations from when i took my private lisc. But this should help.

    http://www.raeng.org.uk/publications...aft-navigation
    Last edited by Ashy; 17Dec14 at 23:00.
    Adapt.... Improvise.... And Overcome....
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  4. #3
    Magnetic variation is modelled, wind drift certainly is (if the mission has wind). Magnetic deviation, not 100% sure, but I don't think it's modelled.

    Don't try and navigate 120 NM for starters, navigate between "waypoints" a shorter distance apart, and make those waypoints geographic features that you can see, both on the map and with your eyes when flying. That way an error will be much smaller and you'll be able to correct for it quickly and easily.

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    Junior Member smoke's Avatar
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    Ashy - Thanks, I use an E6B app on my phone for time/distance traveled, and the stop watch on the dashboard clock in cockpit. No charts though, just pull the Azimuth and Distance from the Mission Editor.

    Eddie - I would normally use geographical references as check points, and set a backstop if I were traveling degraded, Last night I was just bored and trying to see how far I could travel accurately.

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    GOMER 2 Noodle's Avatar
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    DCS does simulate magnetic declination (or variation, if you prefer), but it does not simulate magnetic deviation. This should actually make your life easier, assuming you're using the mag compass to perform your dead reckoning. If you're using the DG/HSI, it's not generally affected by deviation.

    The problem is that DCS uses a flat Earth model, and because of the projection used, the further you travel from the origin of the map, the greater the distortion. The result is that headings are skewed slightly. Not a big deal when traveling between fixed waypoints using the EGI, but a an awfully big deal when dead reckoning with a mag compass and a stopwatch.

    There have been multiple attempts to decipher what exactly is going on in DCS with regard to magnetic headings, but its a puzzle that rewuires some study to understand. The short of it is: magnetic deviation is variable across the map; magnetic headings are displayed differently depending on which airframe you're flying; there are physical misalignments and geographic positioning errors in many scenery objects such as airports; the issues are too complex to fix in the current map.

    I think (and hope) that EDGE will fix these issues for future maps by allowing a spherical Earth model using an accurate spheroid. But we'll have to wait and see.

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    Senior Member Baxter's Avatar
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    We now to go to Ollie Williams with his DCS report...Ollie?

    image.jpg

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    Dojo (18Dec14), Eddie (18Dec14), El_Roto (18Dec14), Trigger (18Dec14)

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