BTG File

What are BTG files and how to open them

Are you having problems opening a BTG file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your BTG files.

What is a BTG file?

A .BTG file is a Binary TerraGear - FlightGear Scenary Data file.

Binary TerraGear scenary data stores 3D terrain and scenery used by the FlightGear flight simulator. It is created by the TerraGear tools during scenery generation for FlightGear, typically for representing terrain surfaces, airport geometry, and static objects in world tiles. FlightGear loads this data at runtime to render landscapes and structures.

The format is produced by TerraGear, which takes as input elevation data, land-use data, airport layouts, and other geographic sources, and outputs one or more binary terrain tiles in this format. These tiles often accompany ".stg" files that define scenery tiles, referencing these binary terrain data files as their terrain source or as airport inset files. The data is often compressed (gzipped) to save space.

Internally, the file begins with a header containing version number, a magic identifier "SG", creation timestamp, and the number of top‐level objects. After that follow a sequence of objects each with a type (such as vertex list, normal list, texture coordinate list, color list, triangles, triangle strips, fans, points), property list (for example material and index types), and element list referencing previously listed vertices/normals/etc. Coordinates are cartesian and stored as single-precision floats relative to a bounding sphere (which itself uses double-precision for the center). Texture coordinates are floats between 0.0 and 1.0 (wrapped if out of range), and normals are stored as triplets of signed bytes mapping into −1.0…1.0. Files are little-endian.

This format's internal identifiers include a version (currently 7 or 10), magic number 0x5347 ("SG") right after that, and object headers that use single byte type codes (e.g. 1 for vertex list, 10 for triangles, etc).

How to open BTG files

Important: Different programs may use files with the BTG file extension for different purposes, so unless you are sure which format your BTG file is, you may need to try a few different programs.

While we have not verified the apps ourselves yet, our users have suggested two different BTG openers which you will find listed below.

Last updated: August 25, 2026

Various apps that use files with this extension

These apps are known to open certain types of BTG files. Remember, different programs may use BTG files for different purposes, so you may need to try out a few of them to be able to open your specific file.

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