skydemon-airmate-navdata-sync

Keeps the navigation data of a Dynon SkyView up to date: it downloads an Airmate AIRAC cycle, lays the files out exactly the way the Dynon expects them, and copies the result onto every configured USB stick without rewriting the gigabytes that did not change.

Everything specific to a subscription or a machine — the Airmate customer id, the Dynon serial, the AIRAC cycle, the local paths — lives in config.toml, which is git-ignored. The code contains no ids.

Requirements

• Python 3.11 or newer (the config reader uses the standard-library tomllib)
• An active Airmate subscription bound to your Dynon serial

Setup

Either install the release, which puts a navdata-update command on your PATH:

pip install airmate-navdata-sync
navdata-update --init-config      # writes ~/.config/navdata-sync/config.toml

or work from a checkout, which keeps everything in one folder. pip install -e . installs the dependencies from pyproject.toml and links the package in place, so edits take effect without reinstalling:

git clone https://github.com/Natim/skydemon-airmate-navdata-sync
cd skydemon-airmate-navdata-sync
python3 -m venv .venv && . .venv/bin/activate
pip install -e .
cp config.example.toml config.toml

Then edit the config file. The two values you have to fill in are in the [airmate] section:

• id — the customer id in your personal download URLs (https://www.airmate.aero/download/navdata/<id>/...), visible on the Airmate download page once logged in.
• serial — the serial of the Dynon the subscription is bound to. It is the number embedded in the filenames Airmate offers you, as in airmate_av_data_eu_2608_<serial>.dup and CHARTS-<serial>.key.

If you would rather not keep those on disk, leave the placeholders in place and export them instead; the environment always wins over the file:

export AIRMATE_ID=... AIRMATE_SERIAL=...

Every other setting is documented inline in config.example.toml.

Without --config, the first of these that exists is used: ./config.toml, then ~/.config/navdata-sync/config.toml (honouring XDG_CONFIG_HOME), then config.toml at the root of a checkout.

Usage

navdata-update                 # download the configured cycle, then stage it
navdata-update --list          # show which files the config resolves to
navdata-update --cycle 2610    # try the next cycle without editing the config
navdata-update --skip-download # rebuild the staging folder from the cache
navdata-update --sync          # copy staging onto the USB sticks

From a checkout without installing, ./navdata-update.py and python -m navdata_sync take the same arguments.

Without --sync the run stops after staging and prints the configured USB mounts, so you can inspect the result first. A later --sync reuses downloads_prepared/ when it already matches the configured cycle (no second unzip of the plate bundles). --skip-prepare forces that reuse; if staging is missing or was built for another cycle, the folder is rebuilt.

Downloads are resumable and run four at a time behind one global progress bar; interrupting the script and running it again picks up where it left off. Files that are already complete are skipped, with one deliberate exception: the CHARTS-*.key file is always re-fetched, because its contents change every cycle while its size stays identical.

Keeping the configuration current

Two things drift and need a manual edit:

• data.cycle — the AIRAC cycle, as <two-digit year><two-digit cycle> (2608 is the 8th cycle of 2026). It changes every 28 days.
• data.raster — raster VFR charts are named after their edition date (VFR-FRANCE-OACI-16APR26.dcf), which is unrelated to the AIRAC cycle. Copy the new filenames from the Airmate download page when an edition is published.

--list is the quick way to check what the current configuration points at before starting a multi-gigabyte download.

What ends up on the stick

AIRMATE_AV_DATA_EU_<cycle>_<serial>.DUP    navdata (uppercased, the Dynon is picky)
AIRMATE_OBSTACLE_DATA_EU_<cycle>_<serial>.DUP
CHARTS-<serial>.key                        unlocks the chart and raster layers
ChartData/Plates/...                       approach plates, from the region zips
Raster/VFR-*.dcf                           raster VFR charts

The copy checksums each file (blake2b) and writes only those whose bytes actually changed, in 4 MiB sequential chunks via aiofile. The staging folder is rebuilt from scratch every run, so timestamps are always new and a size+mtime comparison would recopy everything. Full sequential writes of changed files are easier on a FAT-32 stick than rsync's random block deltas, and opening the destination in place avoids a temp copy on a nearly-full volume. Several sticks (left and right SkyView) are updated in parallel, each with its own sequential writer.

Repository layout

pyproject.toml             packaging metadata, distributed as airmate-navdata-sync
navdata-update.py          entry point for a checkout, mirrors the installed command
config.example.toml        documented template for the git-ignored config.toml
navdata_sync/
  config.py                finds and validates config.toml, applies env overrides
  catalog.py               turns the config into the list of URLs to fetch
  download.py              resumable parallel downloader
  prepare.py               staging into the Dynon layout
  usb.py                   checksum-and-copy onto one or more USB sticks
  cli.py                   argument parsing and the run sequence
tools/
  mbtiles_to_dcf.py        converts an MBTiles file into an Airmate-style .dcf

tools/mbtiles_to_dcf.py is a standalone experiment, not part of the update flow, so it ships in the source distribution and the checkout rather than in the wheel. It builds a .dcf raster layer from any MBTiles source; note that a layer is only displayed if a matching entry exists in CHARTS-<serial>.key, which the script cannot create. It needs Pillow, from the mbtiles extra (pip install -e '.[mbtiles]' in a checkout); run tools/mbtiles_to_dcf.py --help for the options.

Releasing

pip install build twine
python -m build            # writes dist/*.whl and dist/*.tar.gz
twine check dist/*
twine upload dist/*

The version lives in navdata_sync/__init__.py and is read from there by the build backend, so bump it in that one place.

Development

pip install -e '.[dev]'
pre-commit install
pytest

pre-commit runs the same hooks as the GitHub Actions lint job (ruff, typos, YAML/TOML checks). CI also runs pytest on Python 3.11, 3.12 and 3.13.

A note on the data

The navdata is licensed per subscription and tied to your Dynon serial. Keep config.toml, the downloads and the staging folder out of version control — .gitignore already covers them. And, obviously: this is a personal convenience script, so verify on the unit that the cycle you expect is the cycle it loaded.