FSX-SE Magnetic Declination Errors

[jmdriskell 178]

I live near KSEA whose declination is about 15.61° E.  I fly FSX-SE and have applied Hervé Sors latest magnetic declination corrections. I get a variety of course directions using flight plan tools.  For instance, I built a flight plan from KSEA to KBOI via V4 using Flight Sim Commander Version 10.0 Rev 5 Build 06.03.2018.  The first leg of the flight plan from SEA to YKM shows a course of 108-110° magnetic.  The Seattle Sectional Chart shows V4 as constant 104°.  FSTramp shows a course of 105°.  The sectional chart is correct, so how do we explain the variation between the Sectional and Flight Sim Commanders course of 108°?

Does anyone know if it's possible to update Flight Sim Commander to use the correct magnetic declination variables?  Everything else seems to be within limits.

Thanks in advance for your help.

Jim Driskell

[PHYZ1X 0]

NOAA released an out-of-cycle WMM update earlier this year for faster-than-expected magnetic field variations. I would assume that the sectional chart is using that update, but Flight Sim Commander is probably using an older model (either WMM2015 or IGRF12). You might be able to dig through the Flight Sim Commander directories for the WMM coefficient table and either manually update it or overwrite it - NOAA openly publishes these tables and most codes making use of them simply parse them for relevant values. I suppose there's an outside probability that table is buried in some un-editable code, which would be worst-case-scenario for accomplishing your desire here.