The HAB Bounder is frequently used to geofence balloon flights. This article looks at some of the settings available on the HAB Bounder when using its GPS on weather balloons and how they can influence a geofence trigger.
When should I add the low-power GPS option to the Flight.cfg file?
A low-power GPS option has recently been added to the HAB Bounder’s firmware (Sept 2023). When this option is enabled the HAB Bounder’s power consumption is reduced by about 20%. On version 5.2 hardware this increases the maximum duration from about 100 hours to 125 hours. At least on flights where the battery heaters are not required.
This low-power GPS option is not the default because it comes with three downsides:
- First, it reduces the GPS position solution rate from 2 Hz to 1 Hz. With balloon flights this usually isn’t much of an issue.
- Second, it disables the receiver’s ability to use satellite-based augmentation systems (SBAS). This significantly reduces the GPS position accuracy (down to about 30 meters) and removes an integrity check.
- Lastly, it can result in lost GPS position fixes for a couple of seconds at a time. This occurs when there is poor satellite coverage, which is not a concern at altitude.
On longer-duration flights with loosely-defined geofences these downsides usually aren’t much of an issue. To enable the low-power GPS option add the following line to your Flight.cfg file before any “Command:”
GPSLowPwr:Why does the HAB Bounder take so long to start?
The HAB Bounder needs to first acquire GPS time so it can create date and time stamped log files. Once it acquires GPS time it plays the intro to Beethoven’s Für Elise. Afterwards it then proceeds to load and verify the Flight.cfg file. Under ideal conditions this Time To First Fix (TTFF) can occur within about 30 seconds.
However, in normal usage it usually takes the HAB Bounder about three minutes to acquire GPS time and position. Both usually occur together so that Für Elise runs into Bach’s Toccata and Fugue in D Minor. The later indicating a good GPS position fix.
To decrease the amount of time it takes the HAB Bounder to start, place it upright in an location with a open view of the sky. If it still hasn’t acquired a fix within 15 minutes, briefly remove a battery to power-cycle it and turn it back on. Sometimes the GPS module’s acquisition engine seems to get confused and this helps reset it.
