All .bgl files used for navigational data in gauges follow the following file naming format:
aa9#####.bgl
(a = alphabetical, # = number)
Could that 9 after the first two letters stand for Flight Simulator version 9 maybe?
I've also noted that each geographic folder in the Scenery folder, such as Eurw for Western Europe, has many of these BGL file ##### numbers starting as 39170. For example all the AP9#####.bgl (airport BGL remember) files start from 39170, all the AB9#####.bgl files start at 39170, all the HL9#####.bgl (coastline data I believe) start at 39170 and so on. Then if you look in the North America - Central folder (which is Namc), the files have a ##### number starting at 18080. The rest of the other folders similarly have their own unique 'starting number'. I'd say that's a good place to start to try and guess at what indexing system is in use.
nv9AFRI0.bgl (I guess this is Africa region)
nv9ASIA0.bgl (Asia)
nv9AUST0.bgl (Australia)
NV9EURE0.bgl (Eastern Europe)
NV9EURW0.bgl (Western Europe)
NV9NAMC0.bgl (North America - Central)
NV9NAME0.bgl (North America - Eastern)
NV9NAMW0.bgl (North America - Western)
nv9OCEN0.bgl (Oceana)
NV9SAME0.bgl (South America)
You might be pleased to know the navaid database is actually stored in plain XML files that are then compressed into these BGL files by Microsoft's BGL compiler tool, as found in the Scenery SDK.
The uncompressed .bgl files load very nicely into Visual Studio .Net 2003 too. Once loaded you can simply use VS.NET's file editor to view either the plain XML or a Data view (click on the XML or DATA tabs at the bottom of the editor window). In DATA view mode you can see that each XML file contains the following tables:
FSData
SceneryObject
LibraryObject
Ndb
Vor
Dme
Airspaces and Political Boundaries are in the \Scenery\... geographic folders,
and contain the specific drawing instructions!
AT9NAME0.BGL is the filename used for each of the geographic areas. After decompiling the file with NewBglAnalyze.exe, I can now see all of the data for *all* types of airspaces, along with coastlines and political boundaries... ;)
Example:
type="CLASS_C"
name="CHICAGO MIDWAY">
lat="N41 45.35000"
lon="W087 38.91683"
minimumAltitudeType="MEAN_SEA_LEVEL"
altitudeMinimum="579.12"
maximumAltitudeType="MEAN_SEA_LEVEL"
altitudeMaximum="1096.97"/>
lat="N41 41.61667"
lon="W087 34.01683"/>
lat="N41 47.15850"
lon="W087 45.14167"/>
type="CLOCKWISE"
index="0"
lat="N41 44.51667"
lon="W087 58.03349"/>