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MagVar

Messages
216
I would need some help with magvar related issues.
If jvile is around, I would really appreciate his input as I understand he is an authority on the subject.

Please confirm or not:
  1. magdec.bgl provides magvar only to aircraft and airport (i.e. runways, ILS, terminal navaids if any)
  2. VOR and NDB get their magvar through NVXxxxxx.bgl files

Open questions:
  1. with madec.bgl updated, when opening any stock airport, I still see (at the airport properties) the original (stock) magvar and not the new one. Does this mean that there is no update (so everything at the airport still works at the stock magvar), or is it just a non-updated display and in action everything works on the updated magvar?
  2. Addon airports (declared in scenery library through AddonScenery) use the magvar displayed
in the airport bgl, or a value obtained by magdec.bgl?
 
Messages
8,893
1. magdec.bgl provides magvar only to aircraft and airport (i.e. runways, ILS, terminal navaids if any)
2. VOR and NDB get their magvar through NVXxxxxx.bgl files

True

or is it just a non-updated display and in action everything works on the updated magvar?

Its just a non-updated display that is not used.
 
Messages
216
jvile,

thnx alot for your input.

So I presume that even addon airports use the value in magdec.bgl, and not the one declared in airport properties. Am I right?

Last question (that emerged in the meantime):
the way these values (magvar in magdec.bgl and navaids files) are been used depend on the propriatory code of each addon aircraft (for updating onboard navigational instrumentation), or is it somehow FSX-hardcoded ?
 

scruffyduck

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If an addon is created from a stock airport then chances are that the magvar of the stock is going to be used.

If you create a new airport in ADE then it will do a search to try and get a magvar for you (there is a choice for ADE to find it in the new airport dialog) All it is doing, however is searching its databases for the nearest stock object that has a magvar and uses that. This may be good or not. However given the very limited use made of magvar in airports it probably does not matter.
 
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216
... However given the very limited use made of magvar in airports it probably does not matter.

that's what I understand from your input; that, at the end of the day, the magvar declared in an airport is not used. What is actually used, for everything related to the airport, is the value in magdec.bgl.

So why this field does even exist in airport/ILS properties?:confused:
 
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spain
I guess the mag variation don't matter, because can't be actualized, I mean this is a fix mag var. this would be a huge task to actualize every local mag var every year, but of course the question is interesting, could be actualized ? and how.
 
Messages
8,893
that's what I understand from your input; that, at the end of the day, the magvar declared in an airport is not used. What is actually used, for everything related to the airport, is the value in magdec.bgl.

So why this field does even exist in airport/ILS properties?:confused:

There are many fields used in both FS9 and FSX that are not used. Sometimes the SDK will tell us what we need to know such as pushback = NONE, BOTH, LEFT and RIGHT are not implemented.

In other cases the SDK says nothing and leads us to believe the values are used. We can only assume at this point that MS had intentions of using all the mag values per individual attributes but never got around to implementing it.

In ADE Jon will ghost certain windows and show the data but you can not change it at that level of airport design. You see this when you open the property window of the Localizer (Mag Var). In this case even if you could change the Mag Var of the Localizer it does nothing as you already know.
 
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us-arkansas
So why this field does even exist in airport/ILS properties?:confused:

My wild a$$ed guess is that MS put the field there so that someone working with a magentic heading for a runway would be able to see how much to shift the true heading to get the runway right.

My view has always been that it was information for us to view, not information for us to modify or for FS to use.
 
Messages
216
My wild a$$ed guess is that MS put the field there so that someone working with a magentic heading for a runway would be able to see how much to shift the true heading to get the runway right.

My view has always been that it was information for us to view, not information for us to modify or for FS to use.

That can be an explanation. Maybe, in this case, magvar in airport properties should also be greyed out.
As a general remark; in an ideal world, all that would be needed would be a unique magdec.bgl file for all use. MS kept effective airports data on this global source of data (which matches RW as airport charts are updated on a monthly basis and current magvar is normally respected), but kept navaids magvar on a separate source. An explanation for this, could be that they tried to simulate RW inaccuracies (i.e. there are indeed RW navaids calibrated with non-current magvar, so I assume that RW pilots who use them routinely see a standard inaccuracy, as much as the diff between calibrated magvar and current magvar).

... Sometimes the SDK will tell us what we need to know such as pushback = NONE, BOTH, LEFT and RIGHT are not implemented....

is there actually any SDK documentation? could you direct me to a source?
I was not able to find anything in these issues in ESP, so I presume is a separate document.

Is there any input on this:
"the way these values (magvar in magdec.bgl and navaids files) are been used depend on the propriatory code of each addon aircraft (for updating onboard navigational instrumentation), or is it somehow FSX-hardcoded ? "
 
Messages
216
I guess the mag variation don't matter, because can't be actualized, I mean this is a fix mag var. this would be a huge task to actualize every local mag var every year, but of course the question is interesting, could be actualized ? and how.

Bernardo, I am not sure what you mean by "actualized", but if you mean "updated", this is feasible. See this link http://www.aero.sors.fr/.
Read carefully the author's notes.
 
Messages
216
Thanks, but I have this link.
I was referring to any kind of discussion/explanation documentation (that would go into how the sim engine works), but I guess that this is all.
 
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