Three tools have overlapping names and overlapping reputations, and the documentation does not clearly separate them. This page says what each one is, then lists the nine places the project’s own documentation disagrees with itself about them. Four of those nine were settled by building the tools; the answers are marked in the table.

The tools

TerraGear

The command-line toolchain that converts GIS data into FlightGear scenery; fourteen binaries, run in sequence. It is the thing that builds terrain, and it is what the rest of this site documents. A source build takes about twenty seconds once its dependencies are in place; a 1°×1° square takes under a minute after that, or about five with land cover.

TerraGear GUI

A graphical front end, described on the FlightGear wiki as available for those who would like to use TerraGear without knowing or using the command-line options.

It is not part of TerraGear. Building the repository installs fourteen executables and none of them is a GUI, which settles the README‘s claim that there is no graphical front end for these tools: correct about the toolchain, silent about anything shipped separately. Whether the GUI is maintained, and whether a newcomer should use it, is still unanswered.

FlightGear Scenery Designer

A separate project, hosted on SourceForge rather than GitLab, for designing individual scenery tiles through a graphical interface. It does a related job to TerraGear rather than the same one: TerraGear generates terrain in bulk from survey data, FGSD is for fine-tuning a few tiles by hand.

It is not a current option. The FlightGear wiki’s own page on it has recorded since 2011 that it does not appear to be actively developed, the SourceForge project is still marked alpha, and its mailing list archives run out in the mid-2000s. If you are choosing a tool today, this is not the choice: it is here because the name keeps coming up.

Still unanswered. Whether the GUI is maintained, and which of it and the command line a newcomer should be pointed at. Nothing in the repository or the wiki says.

Where the documentation contradicts itself

Documentation accumulates in layers over twenty-five years, and TerraGear’s has. These are listed because a newcomer following the existing material walks into at least one of them, usually within the first hour.

#	The contradiction	What to do
1	The repository `README` documents an `autogen.sh` / `configure` build. The same repository ships a `CMakeLists.txt`, and the wiki documents a CMake build.	Use CMake.
2	The `README` gives instructions for “the CVS version of the source”. The project is on git, at GitLab.	Clone from GitLab.
3	The `README` states there is “currently no graphical front end for these tools”. The wiki documents a TerraGear GUI.	The README is right about the toolchain: a source build installs fourteen executables and none of them is a GUI. Any GUI is a separate project.
4	The `README` documents the GLOBE / GTOPO30 path using `raw2ascii` and `demchop`. The wiki documents the SRTM path using `hgtchop` and `terrafit`.	Use the SRTM path.
5	`README.howto` refers to `genapts`. The wiki refers to `genapts850`.	Resolved: the binary is `genapts`. The string `genapts850` does not occur anywhere in the source tree.
6	The wiki notes `ogr-decode` was “renamed to poly-decode in recent versions” without saying which version.	Resolved: it was not renamed. The tool is `ogr-decode`, and `poly-decode` appears nowhere in the repository at any point in its history.
7	Data source links in the `README` and `README.howto` point at FTP and HTTP servers that have been offline for years. The wiki notes MapServer “has been discontinued” while still recommending downloads from it.	See Where to get terrain data.
8	`README.howto` is headed “Original version by Alexei Novikov, Sep. 3, 1999”. It instructs the reader to edit source files by hand and, for landmass data, to ask a specific person how he does it.	Treat it as history, not instructions.

Why this site exists

The table above. TerraGear works: the square described across this site built in 37 seconds and renders in the simulator, but nothing takes a newcomer from an empty directory to that result without walking them through several of those nine.

Build your first scenery tile is the attempt at that document, and every command on it was run before it was published.