Flying Basics: Magnetic Declination - Implications & Solutions

[@Frogs114]

RW Fligjt instructor here. Great video! A couple times throughout the video you substitute magnetic deviation for magnetic variation. These aren’t the same. Mag Var is the angular difference between magnetic and true north. That was correct Mag Deviation (I remember it by “That DAMN airplane”) is the effect on the compass from interference from the aircraft itself.

[@beanbagninja6224]

This is part of "General Navigation" that pilots have to learn, and I think it's fascinating! Chocolate Dairy Milk Very Tasty!: Compass heading + Deviation = Magnetic heading, + Variation = True heading . Also, Variation and Deviation are two different things; they are not interchangeable.

[@grimreapers]

Go Steve!! x

[@djmitchell2785]

I've recently found DCS and been watching videos and damn, it never fails to surprise me how detailed this game is

[@scarecrow1323]

Thank you so much for the vid, Cap. Thiis has been my favorite video so far. Crucial information and perfect timing. GR Rules.!!

[@grimreapers]

roger. Don't forget that everything is here, listed in various categories: kzbin.info/door/ZuXjkFY00p1ga3UyCBbR2w

[@Proximax9]

never knew this was a thing. I've had problems with this before when landing in bad weather but never did I think it was my instruments showing me wrong, I just presumed I sucked lmao :D now I can start making corrections, finally.

[@-_Nuke_-]

PERFECTLY EXPLAINED also with a bit of spice! Thanks supercap!

[@cmibm6022]

This is essential, but it is also essential that you use the right terminology. Otherwise it is more confusing than not knowing. As said by Dwayne E, there should always be a DEVIATION card (table) near the compass, showing you the magnetic deviation on various headings (eg. by intervals of 10deg heading). That is something you determine by (on a magnetic neutral piece of ground) turning the aircraft (or ship) in various directions and noting the difference from magnetic north. Note that this card is specific to the actual plane or ship and should be checked at least once a year. Thus to find true north from your magnetic compass, you shall add deviation and variation. I do not know if magnetic deviation is implemented in the DCS planes - but you could find out.

[@mariushusejacobsen3221]

Some aircraft in DCS are based around True headings. IIRC F-15C (fc3) uses true. F/A-18C defaults to magnetic for its displays but you can switch it to true. True heading are available in anything that uses INS for its navigation - the thing that makes alignment take so long appears to be that it has to sense what direction north is by feeling the earth rotate. It may or may not display it though, in the F18 you have to ask for it in the HSI page. If you have it sense and store that ahead of time, and don't move the plane, alignments much quicker because it already knows that. Older planes without INS uses magnetic headings exclusively. (Viggen does not have INS; ADR is a different beast. It's complicated.) AWACS calls use true bearings. (LotATC provides options to switch between magnetic and true bearings in its readouts.)

[@Screwball6986]

While the end result is true of what you are saying, this is not in any way what an INS system is doing on alignment. In fact, this very thing you mention is actually filtered out of the INS system, because if it was present, it could not be accurate, so while it is "present" in the measurements being taken, it is actively filtered out. You should probably look up what an INS actually does on startup, might make your understanding a little bit better, as it would be too much to type here. (from someone who actually works on INS systems)

[@mariushusejacobsen3221]

@@Screwball6986 Then I question why so many sources say exactly that. And, at least as displayed in DCS and I think elsewhere, the behavior of several systems in stored heading modes (by various names), where they in essence skip whatever they spend the most time doing at the end. Or is this about a difference in INS systems? Some do some don't, and perhaps you're only familiar with the latter? I can see that some systems may want to filter this out for some of its processes that I don't know about, but it's also the single most reliable way to accurately determine your initial true heading, is it not? I am open to learn, is there any websites I should read, perhaps for ins what radartutorial.eu is for radar? Failing that, any books?

[@AdamLindgrenComposer]

VERY informative video. I forgot this was a thing in DCS in the F14, the RIO (typically) enters in Magnetic Variation before INS takes place, so the F14 I think by default flies to a relatively true heading

[@grimreapers]

thx

[@cmibm6022]

There is a little bit more to it than this. Correct as shown on the WIKI-page: Magnetic variation is the difference between the direction of the (red) compass needle and true north. This value varies (variation) depending on your geographical position . It even varies across the relatively small Caucasus map, where it seems to be between -6 and -8deg. In communication you must agree to use either TRUE or MAGNETIC. I found an interesting quote saying: "What is WRITTEN is true, what is SAID is magnetic (including of course the instruments in the aircraft)". Meaning that whatever you read on a map or in METAR etc. will refer to TRUE north, whereas verbal guidance (eg. AWACS) will refer to MAGNETIC north. Furthermore you can - in the F/A18 change between TRUE and Magnetic: On the HSI go to DATA - go to A/S page - change between TRUE and Magnetic on the right side juts above the middle. I.e. in the air, under AWACS guidance, use MAGNETIC - during landing use TRUE. NOTE: Magnetic deviation seems not to be implemented in DCS.

[@exchatche5823]

Technically there are 3 as far as I'm aware. Grid North is generally very near True North, but not quite exact. Grid and Magnetic are what I've primarily used, Grid for artillery and navigation, and magnetic while talking to aircraft.

[@manu777tube]

Excellent usefull video! This answer more than my question :)

[@phillmurray]

FYI, the Normandy Map is only 1° variation when set to modern day. It's actually around 10°W when you set the date to 1944, which is accurate to the historical magnetic variation of the date.

[@grimreapers]

Wow! That's crazy. That's gunna be hard to get used to.

[@Dimcair]

When figuring out the direction of the runway, just look at the runway number, no need to draw a line. Runway is called 07 = 070 degrees. Runway is called 25 = 250 degrees.

[@preamp51]

Good vid Cap, thx! I was going to comment on the magnetic deviation thing, but others alread did... I will add this though: Every map has a file that stores the magnetic variation over time (don’t remember the file names, I am am not near my pc atm...). As such the variation changes as you change the starting date in the ME. Something you might want you keep in mind when mission building, it would therefore perhaps be a nice service if mission builders would add an approximate variation value in the pre-briefing? Cheers!

[@grimreapers]

thx

[@William3000x]

Awesome explanation. That raised a question on my head, though: When the in-game AI ATCs and AWACS comms give you vectors to a threat, target, tanker or airfield, do they vector you based on True North or corrected for the magnetic variation?

[@grimreapers]

No idea but needs investigating I guess

[@mk014a0003]

Wherever possible, IRL True headings and bearings are used for navigation. If Magnetic bearings were used, then over time, known bearings on charts and briefing materials, such as transits and radials would change, endangering navigational accuracy. Runway names are based on Magnetic bearings and do actually change occasionally IRL. If Magnetic bearings are used on comms, they should be post-fixed with the term "magnetic". e.g. "130 degrees magnetic". In DCS, there are some inherent problems with the map that cause additional issues. Specifically, the region has been projected onto a flat surface, which means that some areas are stretched and some squashed to make it fit which would distend some of the lines of longitude. This problem is not unique to DCS and there is a well known workaround - that is to add a third North in and call it Grid North. In DCS, Grid North is lined up as closely as possible with True North at a single point. This is the North that you see in the F10 map. Set-up of aircraft systems to reflect True North or conversion while in flight is the specific responsibility of the aircraft crew.

[@Lisa-Azra_Broad]

Does this effect mark points? eg in the JF10, I take the decimal co-ordinates of a target, feed those into the front display, link that to the CB6 glide bomb, but the bomb always targets and aims east of the actual target, INS/GPS aligned in plane?

[@Mojje42]

the AI AWACS gives you a heading you can follow from the cockpit.....magnetic? if i'm flying the Su-25 or Viggen and doing intercepts i always use AWACS as both planes don't have A/A radar and AWACS always leads me right on target.... unless i mess up my INS

[@jamieeast4974]

Just try it and let everyone know. would be interesting.

[@Claude-Eckel]

0:21 I understand that you want to use a term that you are more familiar with, but it is still the wrong term, because deviation means something completely different. Declination (also called variation = VAR for pilots) is the angle of deviation between magnetic and true North, while magnetic deviation is the deflection of the compass needle from magnetic North induced in a compass by nearby metals, by local electric and therefore magnetic fields and so on! It has nothing to do with true North other than adding or subtracting an error from the already existing declination, the angle between magnetic and true north. You can't just mix up the two terms and pretend it's one and the same. They are not! Declination is the deviation between magnetic and true North, and the deviation is the error of a magnetic device like your compass, which does not even indicate magnetic North correctly, let alone true North, and thus adds an error to true magnetic North and indicated magnetic North! If that makes sense. So, one means the angle between magnetic and true North, and your chosen term deviation means an angle between your compass needle and magnetic North (if there's any). Not even remotely the same.

[@bradw1808]

I'm not sure if you can help but seeing as the f10 key is so important I keep having this issue with VR where I drop FPS and its now made f10 a risk to use. I've been using the "VR setting" in the options. I also decrease any graphics settings to their lowest just to ensure the least amount of load. Still can't seem to get the issue to stop. My best option is to Alt tab , minimize DCS, wait 15 seconds and then re open the application. I know im asking abit and I'm sure maybe the forms might be a better spot to take this but just wondering if you have come across this or known others, with a fix?

[@TheSquid510]

i get the info to set the TACAN form the charts in the kneeboard thay are listed as magnetic degrees'

[@grimreapers]

thx

[@CarTech433]

so if i am right your plane in cockpit says that your going true north but its not or something?

[@jamieeast4974]

Even pigeons deal with variations, With out Knowing, as it is so slow in changing.

[@rusfeedernoob5441]

This should be explained in the game. IFR landing and dialing in the airfields course without knowing this will be the first encounter to quit the game frustrated.

[@Screwball6986]

Any pilot ever, or any person who has ever taken a lesson, should understand this, Its the reason we change runway numbering occasionally, but the runway number despite it being a representation of a heading, is not a course. This is why we have charted runway headings.

[@Old-Boy_BEbop]

​@@Screwball6986 yes, but the OP's comment is into reference of understanding this. hint forth this needs to be a lesson and i quote "This should be explained in the game". not everyone whose starting out in DCS is a pilot by profession or by hobby. DCS needs to make this become general knowledge and not that of hidden accumulative information over time during playing DCS 1+ years in.

[@asotelles]

wondering why the f16 doesnt show the true heading, I mean, it has gps with the ins

[@grimreapers]

I think it's a legacy thing, airforces so used to using mag that everything is set up for mag including AWACS etc.

[@nonamenowhereski7563]

Damn, I thought I was just going to blow junk up...now I have to learn math, physics and how to read French. Eighteenth-Century Feminist literature will be modeled next, at which point, I will quit.

[@unclejoeoakland]

Grow a pair and suck it up. If you want to win the war, you have to read french feminist theory. However- some of the best relationship advice you can hope for will be found in Sun Tzu.

[@Hairysteed]

Now here's the 100$ question for Cap: exactly what are the _geographic_ poles based on, or are they simply universally agreed arbitrary points? :)

[@Screwball6986]

Nope. The poles are the actual exit points of the longitudinal axis of the planet, you dont need to "agree" on it, it just is... Just like if you spin a top, it spins about its longitudinal axis, on the earth this is called true north/south

[@frederf3227]

Sadly DCS is more complicated than real life. DCS is an X Y Z grid over a traced 2D map projection. Projection distortion is baked into the 3D world. Developers had a choice what to make true north: longitude lines (reality) or ruler. They chose the latter. A simple demonstration of this artifact is that flying along longitude lines isn't true north and flying true north crosses longitudes. In reality this is fundamentally impossible. I'm sure this makes programming a DCS module to actually do real INS math a complete headache. On real Earth the angle between L/L grid and true north is zero by definition. In DCS the angle between L/L grid and true north varies based on location due to map projection distortion. Since magnetic is true north plus variation DCS magnetic heading inherits the map projection distortion causing wrong magnetic heading relative to the L/L grid. Quick example: Vaziani (real) runway has 323 true heading, DCS 315 ruler but angle relative to local meridian line 323. Real magnetic heading might be 6 less so 317 (real world) or ruler minus 6 (DCS) of 309). So real life this runway is named "32" but in DCS we ask why a runway of 309 magnetic can be called "32". As for the comment of the airplanes being based on magnetic: yes and no. Western fighters often display magnetic but any airplane which gyrocompasses an INS (F-14, F-15, F-16, F-18, AV-8B, etc.) determines direction based on the rotation of the Earth which for all intents is true north. In fact these airplanes must be supplied with magnetic variation data values so they can display something very close to magnetic heading outwardly but internally they do all of their math in true. If you were to enter 0 variation in any of these airplanes they would simply show you INS or true heading. Funny enough L-39, MiG-21, etc. has this problem in reverse where it wants to display true heading but only has magnetic sensors so you have to supply variation. And yes F-16 magnetic variation is entered UFC. If you want true heading reference you can simply set this to 0. At the end of the day if you just want to change from ruler to magnetic heading reference in the airplane and you don't fly really weird years like 2100 or 1901 then you can memorize a single adjustment for every terrain. But if you start asking questions like why is true north crossing longitudes or about terrain, why is this runway angled this way when real chart says... then you go down the rabbit hole.

[@grimreapers]

thanks Brian

[@Breal191]

Deviation is something entirely different. Not synonymous with variation or declination.

[@Madmario2006]

@grim reapers, Do you like Metallica?

[@grimreapers]

Yeh I have seen them live twice!

[@Madmario2006]

Grim Reapers me and my dad once went to the concert near Manchester to watch Metallica, I usually listen to it on the way to school now. Death magnets probably the best so far,

[@jamieeast4974]

"POLE SHIFT" Really

[@markotdz9523]

This does not affect me, I believe in flat Earth... I also believe I can fly... what possibly can go wrong 🙂

[@grimreapers]

good point.

[@slowhornet4802]

Exactly. Most sim developers grossly simplify reality and use a sphere because of its many advantages: e.g. you do not have to simulate the end of a map, falling of the map, looking under the map.You do not have to render that giant turtle because it is hidden inside the sphere. All nice tricks to get some extra FPS, but I call it what it is: CHEATING!