VirCru Geofence System update
We’ve had some feedback from VirCru users about the Geofence system and we’re making some improvements. This is an explanation of how the system currently works and the changes we are making to address the feedback.
How It Works
The VirCru Hub has an integrated GPS receiver that provides a position fix once per second. Low power consumption is at the core of the VirCru system so to avoid the GPS using too much power we have a set of rules which dictate how the GPS receiver is used under different circumstances:
No External Power – VirCru Hub running from internal backup batteries
Power up the GPS receiver for a few seconds every five minutes for a few seconds to get a position fix.
External Power Connected but not Charging
Power up the GPS receiver for a few seconds every two minutes for a few seconds to get a position fix.
External Power Connected and Charging
Keep the receiver powered up permanently.
Whilst the GPS receiver returns a position fix within a few seconds of being turned on (called a hot start) this fix tends to be quite noisy. Typically if the GPS receiver is powered up all of the time we get positional errors of up to 10m but if we are relying on a hot start to get a quick position fix to save power, we get errors of up to 70m. The GPS receiver needs to be powered up for a few minutes before these errors reduce and the position fix stabilises. These figures also assume that the hub is installed sensibly with nothing more than a bit of fibreglass, glass, wood or plastic between it and the sky.
In an effort to reduce the likelihood of false triggers from the geofence system, we currently limit the geofence radius to be over 100m.
100m is a long way when your boat is at anchor. If being used for anchor drag detection, 100m could easily leave you stuck on a lee shore or allow your boat to collide with your neighbour before it alerts you.
We are going to change the VirCru system to allow the geofence radius to be set as low as 10m. If the radius is set below 100m, the VirCru Hub will keep the GPS receiver powered up permanently while the geofence is enabled regardless of the power supply. This will increase power consumption somewhat (exact figures will be confirmed) but it will still be pretty low – somewhere in the region of 35mA. This equates to a power consumption of 0.84Ah per day if the geofence is enabled and set to a radius below 100m so even a modest domestic battery on a boat should last months. The app will warn you of this increased power consumption when you set the radius below 100m and will also recommend that it not be set below 20m to avoid false alarms. The increased power consumption will only impact boats whose batteries are not being charged at the time (by shore power, wind, solar, alternator etc.) as the GPS receiver is currently permanently powered up when charging anyway.
We will be releasing a new build of firmware to all VirCru Hubs and to the App before the end of February 2023 to enable these improvements.