It's pretty bright line that no warrant is required under current law.
Like it or not, since the 1980s it has been the law that from "public airspace" police can use any visual technology to look at the outside of your property. Right or wrong, it's pretty settled law that if the public can fly somewhere then law enforcement can also fly there without a warrant.
https://en.wikipedia.org/wiki/Florida_v._Riley
Ciraolo is another case where police, without a warrant, intentionally flew over a backyard that was enclosed by a fence. In that case, the police found marijuana plants growing. The court upheld the conviction.
https://en.wikipedia.org/wiki/California_v._Ciraolo
The interesting question is what about infrared and other "through the wall" technologies that give an indication as to what's inside a structure. In Kyllo, the Supreme Court decided 5-4 (with Scalia writing the majority opinion) that using a thermal imaging camera to investigate heat emitted from the wall of a house was a "search" that required a warrant.
https://en.wikipedia.org/wiki/Kyllo_v._United_States
Like it or not, since the 1980s it has been the law that from "public airspace" police can use any visual technology to look at the outside of your property. Right or wrong, it's pretty settled law that if the public can fly somewhere then law enforcement can also fly there without a warrant. https://en.wikipedia.org/wiki/Florida_v._Riley
Ciraolo is another case where police, without a warrant, intentionally flew over a backyard that was enclosed by a fence. In that case, the police found marijuana plants growing. The court upheld the conviction. https://en.wikipedia.org/wiki/California_v._Ciraolo
The interesting question is what about infrared and other "through the wall" technologies that give an indication as to what's inside a structure. In Kyllo, the Supreme Court decided 5-4 (with Scalia writing the majority opinion) that using a thermal imaging camera to investigate heat emitted from the wall of a house was a "search" that required a warrant. https://en.wikipedia.org/wiki/Kyllo_v._United_States