10 meters accurate is very well doable with GPS. So that's settled, just use a GPS receiver on all the things you want to track.
The real problem is how are you going to get the GPS data to the Arduino that's way up in the air? (and why is that Arduino there in the first place?)
1 km is quite a distance. You'll have to look into wireless communication, and that 1 km distance is the minimum - straight below - if you move 1 km along the surface of the earth you end up at 1.4 km total distance. Line of sight shouldn't be too much of an issue.
Easiest solution for tracking these objects over these distances within required accuracy: smartphone + app that sends GPS details back to your master over the mobile phone network.