Magnetic declination - how does DCS handle it?

Disclaimer:

Before reading the following paragraphs please note that I'm not trying to be nitpicking, but rather establish a more robust understanding of a certain aspect of DCS and DCS as a whole.

Situation:

Hi, I recently tried to brush up on my navigational skills in the Mi-8 and attempted to plot precise courses. I knew about magnetic declination - the difference between a TRUE heading (referencing towards the geographic north pole) and a MAGNETIC heading (referencing towards the magnetic north pole) - and tried to apply the deviation. (As a matter of fact, the training mission for the Mi-8 regarding the DISS-15 navigation system mentions a deviation of 6° East).

However I still drifted away from the course indicated by onboard systems such as the DISS-15 doppler navigation and the NS430 GPS-module. Especially if I only relied on the DISS-15, the deviation was around 0.5 to 1km per 10km flight path. I tried to minimize the course error due to crosswind, but still couldn't reliably reach my destination with only a few hundred meters navigational error, but rather offset by at least several kilometers.

Research:

Reading upon this topic I found out that the magnetic north pole is currently shifting several miles per year from northern Canada towards Siberia. I found particular interesting information about this topic in THIS THREAD. This in return means that the magnetic declination for any point of earth changes over the course of time. This information may already be known to some/many of you, however it came to me as a surprise, hence my questions regarding this matter.

Problem/Question:

I am wondering what the modeled magnetic declination in DCS would be for any map at any given time.

1. Does DCS include changes to the deviation every year to depict actual magnetic declination?
   
2. If not, how does DCS depict the magnetic declination? Is it a fixed value for each map?
   

My own testing has shown that I get about 4-5° deviation between my HSI (magnetic heading) and the displayed heading on the F10 map and F2 status bar (probably true heading). In contrast the "real life" magnetic declination for Vaziani and Gelendzhik ranges from 6.6° to 7.26° (see also https://www.ngdc.noaa.gov/geomag/calculators/magcalc.shtml#declination).

Conclusion:

My goal is to improve my navigational abilities and to account for magnetic declination accordingly, so that I may reach any target area with a minimal amount of discrepancy; and in order to achieve that goal I would like to hear your input and thougts on this matter.

Thank you.

EDIT:

After much, much more research and browsing through relevant information I found this post explaining most of my questions. (However I do not know if the information is still accurate since the post is from 2014, before any map updates and before 2.5).

Still, I am curious about the ongoing change of magnetic deviation each year, which needs to be taken into account if a mission would take place several years in the past or future. In other words, does DCS calculate the correct magnetic deviation based on the mission date?

Nice write-up!

Two possible scenarios for you that aren’t related to the declination:

1. I don’t have the Mi8, but I fly another type of helicopter in real life that is equipped with Doppler. It is not a very accurate system and is very prone to drift. When we are flying on Doppler, we update it’s position using a known point in flight every 10-15 minutes. This would account for the Doppler being worse, as you’ve said.

2. Does your mission have any winds? If it has wind and you are not accounting for that, then that will cause drift on its own. Even a very light wind will have a significant effect over a distance.

As for DCS handling of variation, I’m not entirely sure how it handles it, but perhaps your issue is more related to one of the two points above?

Another thing to be aware of (I've said this before, but I'll say it again here - pretty sure the references post talks about it also): what DCS calls "true north" is not lined up with earth parallels. If you follow a true north heading, your longitude will change (you can see this in the mission editor: "true north" is always up - check with the ruler - while you can see the geographic grid is not).

Note that this does not cause too much issues (except for headaches), usually. I don't know how or if it affects the NS430 as I don't have it.

DISCLAIMER: I am not an expert, I just got interested in this thread and did some googling and sifting through the data.

The data in DCS files mentioned above is from the WMM 2015v2 data at https://www.ngdc.noaa.gov/geomag/WMM/soft.shtml

It is very likely DCS uses the C code provided there for download in order to interpolate declination values based on the model. If you want to control what you get, I recommend setting your mission date to the reference date for the 2015v2 file (12/15/2014) then you should be able to replicate the value DCS gets from the model (without adding the "change per year" values that we don't know whether DCS uses.) For example, using this calculator: https://www.ngdc.noaa.gov/geomag/calculators/magcalc.shtml#igrfwmm

[edit: maybe use 1/1/2015 for your mission date instead, in case DCS selects the older model data if before 2015, that might be safer]

I think you will find that the entire Caucasus map is basically -6 degrees and the entire Persian Gulf map is -2 degrees. You can look at the iso lines for the 2015v2 data here:

https://www.ngdc.noaa.gov/geomag/WMM/data/WMM2015/WMMMaps2015v2.zip

Look at the D_MERC map (magnetic declination iso lines, mercator projection)

PS: I am no longer sure what the 'date' is set to for the maps shown in the last download that I linked. It says 2019 on the pages, but it doesn't clarify if that is just because they are published in 2019 or (more likely) the input date was set to 2019, so annual changes were applied. The format of the date as "2019.0" suggests this is the date input parameter, since that is the format they use in the online calculator. So now I don't know if DCS uses the annual changes (probably do, since obsessed with realism) so maybe you need to use 1/1/2019 as your mission date to match the maps.

GNS-430 has magnetic declination data from satellites, but it does not exist in the game. In F-18C HSI-DATA-A/C, it can view magnetic declination data.

I am pleasantly surprised that ED implemented a declination that follows the yearly variations. I always thought that the declination in DCS was the one in 2008 or 2011. ED never communicated on this since the last post I saw about this for Black Shark 1!

Thanks for sharing your findings. I'll try to make the best of it to point my MiG-21 in the right direction.

WOW!! And all this time I thought it was just because I couldn't hold a fargging heading!! :megalol: Thanks for the great explanations for all this stuff. Now I feel a little better about my sloppy flying. :pilotfly: Seriously though, this has been very enlightening. :thumbup:

It will be very interesting and usefull that ED put a converter tool integrated on the map/F10 and the Editor, so you would have not to worry about the place and the year to calculate magnetic headings.

Now, Map/F10 have interesting tools like calculating the decimal latitude and longitude and more (using ALT + Y), so why not a tool like I have mentioned before?

Please ED team, keep that in mind.