Upstream state, August 2026

Checked 23 August 2026, against eba49f266f75c81b7d97938e6f24d46ed3df5019 on next. The tools were compiled here and taken through a whole build; the full record, including raw logs, is on the sources page.

The project is active

1,418 commits total. 25 landed in 2026 before the end of August, 19 in 2025, 46 in 2023, and one contributor accounts for roughly nine tenths of the last three years.

The first evidence a newcomer meets says otherwise: the GitHub mirror’s last push was 18 April 2022, it is not marked archived, and it is usually the first search result.

Branches

git clone gives you next. The FlightGear wiki still directs people to scenery/ws2.0, which has not moved in over three years.

Three open defects

All three were hit while building and running the toolchain, and all three are reproducible. Full detail and verbatim output on Common errors and fixes.

1. next does not compile. Commit bf79e24, dated 18 June 2026, dropped a <chrono> include from hgtchop.cxx and left four uses of std::chrono behind. The branch has taken further commits since without this being caught. One line fixes it.
2. genapts hangs on a gzipped apt.dat. Its --help says gzip is supported; the version check reads gzip and the scheduler that follows does not, so the file is accepted and then scanned as binary indefinitely. No error, no output.
3. genapts segfaults above about four threads. Airports in a bucket race each other writing one shared chop.idx. At ten threads it failed all twelve attempts, leaving between 0 and 24 of 31 airports behind with exit status 139.

None had been reported upstream at the time of writing. Reports are drafted and will be filed on the project issue tracker; this entry will be updated with their status.

Also as of this date

• SimGear next cannot be built headless; a canvas test compiles even with -DENABLE_TESTS=OFF. release/2024.1 works.
• The README‘s preferred SRTM download URL returns 404, not a login prompt.
• The official Docker images flightgear/terragear:latest and :ws20 exist and were last pushed in 2019: seven years behind the source.
• The repository carries no version tag. The version file says 2024.2.0; the only two tags are genapts and newconstr.

What a build produced

A single degree over the San Francisco Bay, start to finish in 37 seconds: 44 .btg.gz files, 3.5 MB, 115,989 vertices, 31 airports including KSFO. Stage timings and hardware are on Hardware and build times.

A second pass added ten land-cover layers from OpenStreetMap and Natural Earth and dropped --ignore-landmass. The same square then took 286 seconds in tg-construct alone, peaked at 2.2 GB resident and produced 50 MB. Land cover, not area, is what makes a TerraGear build expensive: see ogr-decode.

Both builds were then loaded in FlightGear 2020.3.16 and render correctly, including the land-cover tiles, which are BTG version 10, a format whose support reached SimGear well after 2020.3 was released. They were expected to fail and did not. The renders include a control on empty scenery, since the base package ships nothing for that area.

One further note from that pass: ogr-decode --spat selects features whose bounding box intersects, and hands them over whole. Natural Earth’s land layer holds a feature that spans the globe, so a request for one Californian degree had the tool tessellating Antarctica. Clipping with Clipping with ogr2ogr -clipsrc beforehand cut the same work to 0.02 seconds. Worth knowing; arguably worth a note in the tool’s own help.