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.
Does DCS include changes to the deviation every year to depict actual magnetic declination?
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?