• Which the release of FS2020 we see an explosition of activity on the forun and of course we are very happy to see this. But having all questions about FS2020 in one forum becomes a bit messy. So therefore we would like to ask you all to use the following guidelines when posting your questions:

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Why are there so many different formats for BGL files?

How is it that FSX can read so many different formats?
Why isn't there one format and all BGL files conform to that one standard format?

I tried to use BGL2XML to decompile a BGL file and it didn't work, just as I've seen so many others have no luck decompiling BGL files.

This is worth reading: https://www.fsdeveloper.com/wiki/index.php?title=BGL

Actually there is only one 'format' It describes how a file is structured. All bgl files contain a header section which provides information about the contents. The contents consist of a bunch of sections containing data of different types. The type of data in the section is identified by a section ID. Each section contains records and sub records identified by their own ID. But in the same way that a word processor format such as Microsoft word 'docx' tells us how to store a document, there can be many different documents. Here is the decompiled format for a FSX airport: https://www.fsdeveloper.com/wiki/index.php?title=BGL_file_format_(FSX_airport)

The fact is that the actual structure for a bgl file is proprietary and we have never had it presented to us. MS never told us the actual structure (bytes etc) for an airport. So we have had to work it out for ourselves. We don't know everything and every time the sim is updated chances are the contents of the bgl files are going to change. We have to find the changes and make sense of them in the context of what we know based on say the format described in the SDK. A good example is the contents of an airport bgl file in P3D v4 which changed the contents of a taxiway among other things. This gave rise to new 'section' IDs which ADE threw out because it was not told how to handle them. Until we worked out the changes and updated the decompiler this stopped certain things working altogether.

A decompiler such as Bgl2Xml can only read a bgl file if we have managed to reverse engineer the contents. In some respects we are lucky that the actual contents of bgl files representing things like airports has not changed dramatically. For example the formats for the new MSFS2020 might b entirely different and MS would likely not tell us how to read the content.

Different members of the community have been reverse engineering the bgl file for years. Technically we are breaching copyright. So far no one has stopped us. I think MS probably hold the copyright. Over the years I have asked MS to actually provide a decompiler in the SDK so we can stop hacking but that doesn't seem likely, Maybe they are not permitted to do that either.
I was trying to read some P3D V5 BGLs.
My first results indicate a few things have changed (I guess to accomodate the new P3D bgl options such as sloped runways). Anyone has mapped that format?

Jean Luc
yes please send me an email Jon AT scruffyduck DOT org