Near real time GPS synchronization from remote Victron (VenusOS) systems to PostGIS databases for future analysis. Perfect for plotting your off-grid van adventures.

outpost provides highly efficient transmission of GPS data from remote installations to a PostgreSQL database equipped with PostGIS. It's designed specifically for cellular and satellite networks where bandwidth is limited or expensive, and optimization is critical.

The outpost protocol uses a custom binary format over CoAP to minimize bandwith use. Highlights include:

• Delta compression: Position samples are encoded as deltas from a reference point
• Batch transmission: Multiple GPS positions are batched together for efficient transport (up to 40 at a time)
• AES-256-GCM encryption: Secure transmission with pre-shared keys instead of heavy weight TLS

GPS positions are transmited using only 9 bytes per sample (with a 16 byte header per payload). Outpost prioritizes small message size over all else, and thus does not include any kind of system/device identifier. This is trivial to add (and would only require one additional byte per payload), but alas I only have one Victron install/van.

Given the limited range of values representable using only 9 bytes and the diffirent values each position sample encodes, each sample is of limited but acceptable precision:

• Payload header coordinates to 0.0000001
• Cooordinate deltas to 0.0001 or roughly ~10 meters (depending where in the world you are)
• Altitudes in whole meters
• Speeds to 0.1 kilometers per hour

1. Generate key:

   ./tools/generate_key.sh outpost.psk

2. Deploy with Docker Compose:

   export OUTPOST_PSK=outpost.psk
   docker-compose up -d

   This starts:

   • outpost server on port 5683/udp
   • PostgreSQL with PostGIS on port 5432 (local host access only)

   Server logs can be found in .logs/.

1. Copy PSK file to the Victron system

2. Install client:

   ./tools/install.sh --psk-file <your-psk>.psk --host your-server.com --device /dev/ttyUSB0 --baud 38400

   Note: The installer requires pip3 be installed. This is not included in the default Venus image. See here for details on using opkg to install pip.

   The path to your GPS device is highly dependent on your exact system configuration, as is the baud rate. VenusOS only supports GPS devices with a baud of 4800 or 38400, so your device is likely using one of those.

3. Verify installation:

   /etc/init.d/outpost-client status
   tail -f /var/log/outpost-client.log

To update an existing client installation, simply re-run the install script (the parameters used last time need not be added again).

GPS data is stored in the positions table with PostGIS geometry columns. The client automatically deduplicates similar positions before submission to the server.