Switch balloon icon from parachute to landed based on ground level (ruaumoko)

[darksidelemm]

Currently the balloon icon switches from a parachute to the landed icon when the balloon goes below 300m AMSL. Some groups are launching in places where ground level is > 1000m. While the predictions now handle this (thanks tawhiri!), the icon doesn't change.

It might be possible to poll the ruaumoko API every X packets to keep a record of the ground level below the payload (wouldn't want to do this every packet), and use that ground level for the comparison that switches the icon.

[darksidelemm]

Thinking more on this, we could hold onto the last predicted altitude from each prediction, and use that to compare against (if we have data) for the landing icon calculation?