Magnetic derivation

[St3v3f]

I am working on a script that gives the pilot a heading to fly at.

 

Now DCS works with true north while most modules use magnetic bearings. So I need to account for that.

Also, the script is supposed to run in Nevada as well as the Caucasus.

 

Question: Is there a function to access the magnetic derivation at a specific position in the scripting engine?

There is a folder Saved Games\DCS\Data\MagVar\TabularData which sounds a lot like what I am looking for...

Edited April 30, 2016 by St3v3f

[BSS_Sniper]

This may not be the answer you're looking for but I doubt you can fly far enough for the deviation to even matter that much. Having said that, I don't know what the deviation is in this area of the world but I wouldn't think it would be so much that it'll get you lost on our tiny map.

[St3v3f]

It clearly matters. If a direction between two objects is calculated in the scripting engine, it'll be relative to the geographic northpole. Most modules (The rare exceptions I know of are FC3 aircraft and Ka-50) use magnetic headings however.

 

Magnetic derivation in the Caucasus is 6-7° and in Nevada it's more than 10°. So if I send someone heading 070 he will actually be on 080 way of course.

[VTJS17_Fire]

So if I send someone heading 070 he will actually be on 080 way of course.

You can use LotATC, a nice add-on to DCS. It works with true and magnetic headings, also a mixed mode is possible.

[NeilWillis]

Derivation? Don't you mean deviation?

[St3v3f]

Just looked it up again.

Actually, I am talking about magnetic declination, which is the difference of magnetic north and true north.

Magnetic deviation are influences on a compass by local sources, i.e. the aircraft itself.

[Holbeach]

Magnetic Variation.

 

..

[Johnny Dioxin]

Magnetic Deviation :D

 

That derivation thing had me laughing...

 

Yes, I know - but one can still enjoy a laugh, regardless if it's first, third or three hundred and thirty third language!

 

edit - By the way, there's several ways to say this (probably dependant in where in the world you are) but in this case, I'm pretty sure he meant deviation - you could use about 4 other ways to say it, too.

Edited May 3, 2016 by Brixmis

[St3v3f]

Just google it. Declination and Variation can be used synonymous but Deviation ist definitely something else

[codefox]

In case you want to calculate it yourself, grab the coefficients off here: http://www.ngdc.noaa.gov/geomag/WMM/soft.shtml

 

I'd honestly just go with fixed values for each map for now. Won't be much of an hassle to maintain since the amount of maps for DCS will probably not get all too high.

[DeJohn]

Magnetic declination in Las Vegas, Nevada is +11.49°

 

Magnetic declination in K'obulet'i, Georgia is +6.48° (which btw, is what the compass in DCS is off by)

 

You can go to this site to find Magnetic declination anywhere in the world

 

http://www.magnetic-declination.com/

[DeJohn]

FYI:

Before you go adding or subtracting declination to your compass, remember that if you use the F10 map to get a heading, the map is true north not magnetic.

 

Which means if you add 6 degrees for Georgia to your compass, then get a heading from where you are on the map to some point on the map and try to fly there by the compass, the farther you travel, the more off course you're going to get.

 

What does this mean for us?

Flying VFR in clear sky's--- in a helicopter not a whole lot. In most cases you won't be flying far enough that you can't make visual corrections. In a jet, it may or may not become a problem.

 

Flying IFR in low visibility conditions--- It could make the difference between finding you target or home airfield and getting frustrated with the mission. (btw, for a chopper pilot flying IFR means 'I Follow Roads". LOL)

 

An example, If you are flying a mission and the mission audio and/or text is telling to take a heading, and the mission is checking to see if you are flying that heading, then use the +6 degrees.

If the mission doesn't really care what heading you're actually flying, that the heading it gave you was a only reference, then it may not matter, unless you are flying LowVis IFR.

 

If you'd like to check this yourself, download the Huey Hover Practice mission. The first time you run through it don't make the declination correction. odds are it either won't say you passed or it will give you a low score. Then run it again but ADD the declination to your compass, and see if the results are different. (btw, the mission allows you a 5 degree +/- you can be off heading and pass. In the past many people who have run this, changed the mission with the editor and added the 6 degrees to make it 11 degrees +/- to compensate for the difference rather than just set the proper declination, go figure.)

 

If you'd like to check your navigation skills, create a lowvis say 1km or less mission. Start your huey on the runway, bring it to a hover and move to the middle of the runway. Pick a heading, speed, altitude and duration, say 090-80kts-1000msl-10min. At the end of the duration, turn 90 degrees left to 360 and fly for another 10min, turn 90 degrees left 270 and fly 10min, turn 90 degrees left to 180 fly 10 mins. come to a hover as you approach the end of your last 10mins, then reduce altitude and see how close you are to the center of the runway. (make sure you don't use the F10 map to see where you are until you've completed the circuit. Because if you cheat, you're only cheating yourself, and not increasing your skills.)

Edited May 3, 2016 by DeJohn

[St3v3f]

In case you want to calculate it yourself, grab the coefficients off here: http://www.ngdc.noaa.gov/geomag/WMM/soft.shtml

 

I'd honestly just go with fixed values for each map for now. Won't be much of an hassle to maintain since the amount of maps for DCS will probably not get all too high.

 

Thanks, that helped me a lot

 

Wrote a script that will return magnetic variation in radians for a position. The returned value must be subtracted from true heading.

 

Example:

heading = heading - getMagneticCorrection(point)

 

The file must be included via DO SCRIPT FILE

magVar.zip

[Ramsay]

FYI:

Before you go adding or subtracting declination to your compass, remember that if you use the F10 map to get a heading, the map is true north not magnetic.

The F10 map bearings in 1.5.3 are NOT to true north but vary across the map i.e. for DCS level Modules at Krymsk True = F10 + 4°, Magnetic = F10 - 2° (assuming a +6° Magnetic declination to the east)

 

However for grouped objects (runway, ILS approach path, inner/outer markers, etc.) - F10 map bearings = True north

 

EDIT:

So if planning runway approaches or circuits, F10 map bearings can be used for True bearings (magnetic would be +6° east).

 

However if planning a longer flight i.e. to follow RSBN/NDB/TACAN radials, etc. you'll need to correct the F10 map bearing to fly a precise path (or be ~10 km off course after 100 km)

 

Note: Western aircraft instruments/TACAN radials use Magnetic bearings, the L-39 and MiG-21 instruments/RSBN radials use True bearings and FC3 aircraft (Su-25T) instruments/waypoints use game/F10 map bearings.

I'm not sure how this translates to 2.0.2 or how 2.5 (2.0/1.5 merge) will change DCS's quirks.

EDIT 2: For info, Lat/long calculations: http://www.movable-type.co.uk/scripts/latlong.html

Edited May 6, 2016 by Ramsay

[towsim]

If someone uses the DCS map for navigation, he should know, that DCS aligns the map to grid North. All FC3 models show their compass heading with reference to grid north, not to true or magnetic North. The A10 and most of the other full constructed models show magnetic North on their compass. I explained the differences in a post found at http://forums.eagle.ru/showthread.php?t=126899 #10.

In the attached picture it can be seen, that the exact vertical ruler line shows 360° (0°). This behavior is the same at all locations on the map, from far West to far East. True North is always along the meridians and changes from westerly locations to easterly locations.

Magnetic North is bound to any given location and not shown on the DCS Map. It does not reflect the real world variation. The only way to find the magnetic heading for a given runway is to place an A10 as ‘takeoff from runway’ and read the heading from the HSI. On the other hand, all necessary information can be found in the DCS installation folder:

C:\Program Files\Eagle Dynamics\DCS World OpenBeta\Doc\Charts. The charts contain precisely all necessary data for all aerodromes and visual approaches.