Arpa design

[redhog]

When we build the Arpa module for Mayara, we should solve an issue radar_pi Arpa has: Detecting countless targets up on land.

Suggested solutions (all of them needs to be user settings if implemented):

• Do not report targets that geographically are larger than X NM^2 (we might want to handle multiple vessels close to each other, e.g. by checking if the shape of the target changes drastically over time).
• Do not report stationary targets (targets that don't ever move more than epsilon from their first detected position).
• Filter by overlap with known coastline map (how do we get hold of a map on user device, in what format, in radar_pi this might have been more straight forward).