Does anyone know of a way to read the Magnetic deviation values of the waypoints in FS9? I would like to build a table to use with flight planning spreadsheets of my own creation. I have FSNAV (no longer supported :( ) that will display this info, but I would like to read the data directly from the bgl file or some other means rather than reading each way point each time.

Some time ago there was a thread concerning true vs. mag variation when getting forecasted winds aloft and I don't remember the gist of the thread, but it it was basically that MSFS doesn't note the difference, but I don't remember the specifics. Sorry. However, it might be important to note that MSFS does not see the world as a sphere, but as a cylinder. So directions could be distorted. If you fly to the mid point between to VOR's in MS, change to the approaching VOR, you'll have a much greater discrepency than in the RW. Maybe that will shed some lght on what you're trying to do.db.

I believe mag variation was hard coded into FS when it was developed. All VORs North is magnetic North. When the library comes back, up do a search on Collin or the file SC_FREE_SLAVE_GYRO.ZIP (in the gauges category) . The narration there is a good explanation of mag compass and directional gyro. To be brief, there two things that will affect the accuracy of the DG. One is mechanical precession. (there is a check box in the setings menu that will invoke that). The other is flying from one place to another where the variation changes with location. This shows up as the other error in the DG. This little gauge slaves the DG to the mag compass so that when moving thru changing varitaion the DG automatically follows the mag compass. As for your concern, that data is probably in some sort of data base in FS but I have no idea where.Paul

I believe mag variation was hard coded into FS when it was developed. All VORs North is magnetic North. When the library comes back, up do a search on Collin or the file SC_FREE_SLAVE_GYRO.ZIP (in the gauges category) . The narration there is a good explanation of mag compass and directional gyro. To be brief, there two things that will affect the accuracy of the DG. One is mechanical precession. (there is a check box in the setings menu that will invoke that). The other is flying from one place to another where the variation changes with location. This shows up as the other error in the DG. This little gauge slaves the DG to the mag compass so that when moving thru changing varitaion the DG automatically follows the mag compass. As for your concern, that data is probably in some sort of data base in FS but I have no idea where.Paul

The data is encoded in the file magdec.bgl for the whole world. Microsoft confirmed that it's the magnetic variation in this file that is used and the magnetic variation associated with airports and navaids is ignored.

The data is encoded in the file magdec.bgl for the whole world. Microsoft confirmed that it's the magnetic variation in this file that is used and the magnetic variation associated with airports and navaids is ignored.

If you like you can download here an updated magdec.bgl which contains magnetic variations of 2005.This way FS will cohere more with current charts.http://pagesperso-orange.fr/hsors/navaids.html

If you like you can download here an updated magdec.bgl which contains magnetic variations of 2005.This way FS will cohere more with current charts.http://pagesperso-orange.fr/hsors/navaids.html

THanks for all your help. I am looking for a way to de-compile the BGL file into a MagDec look-up table. I suppose if I download the updated BGL file I can search for a 2005 table. Any Idea what year the FS9 is based on? Or is it totaly fictional?

Any Idea what year the FS9 is based on? Or is it totaly fictional?

I think it is 1995 or 1997.There are tools to calculate magvars (not for FS) and if you know the specific year of the FS9 magdec,you could use such a calculator.

The data is encoded in the file magdec.bgl for the whole world. Microsoft confirmed that it's the magnetic variation in this file that is used and the magnetic variation associated with airports and navaids is ignored.

I've heard that the magvar that is encoded with VORs is used to compute the CDI needle deflection. I don't believe there is any convenient way to decode the magdec.bgl file.scott s..

I've heard that the magvar that is encoded with VORs is used to compute the CDI needle deflection. I don't believe there is any convenient way to decode the magdec.bgl file.scott s..

Is this why MS waypoints and VORs etc are way off compared to newer FMS data? A fix for that would be very good as I assume this difference will just increase over time...Is there an equivalent file in FSX (should be newer data), is it similar in structure...?Geoff

I've heard that the magvar that is encoded with VORs is used to compute the CDI needle deflection. I don't believe there is any convenient way to decode the magdec.bgl file.scott s..

There was a post a few years ago that said only the data in magdec.bgl was used in the simulation.That seems sensible because magdec.bgl gives the magvar anywhere so there could be inconsistency between its value and that from an airport of navaid if the latter had their own different values.EDITYou are right. I did an experiment creating a new VOR using ADE9X and it does use its own magvar, not the global one!

I think there have been threads along the lines of "GPS shows one mag course to the VOR, but my OBI shows me off course". that actually makes sense to me, as magvar IRL is always going to change over time, while a VOR is only reset to "mag" north every so often by the operator of it. (and in Canada, there is a "true north" line above which all VORs are set to true north).scott s..

I think there have been threads along the lines of "GPS shows one mag course to the VOR, but my OBI shows me off course". that actually makes sense to me, as magvar IRL is always going to change over time, while a VOR is only reset to "mag" north every so often by the operator of it. (and in Canada, there is a "true north" line above which all VORs are set to true north).scott s..

That may be true in real life but is irrelevant to Flight Simulator where the magvar doesn't change.