[maxlybbert]

The Supreme Court mentioned your question in 2012 in US v. Jones ( https://supreme.justia.com/cases/federal/us/565/400/ ), without giving an actual answer:

“This Court has to date not deviated from the understanding that mere visual observation does not constitute a search. See Kyllo [v US]. ... We accordingly held in [US v] Knotts that ‘[a] person traveling in an automobile on public thoroughfares has no reasonable expectation of privacy in his movements from one place to another.’ ... Thus, even assuming that the concurrence is correct to say that ‘[t]raditional surveillance’ of Jones for a 4-week period ‘would have required a large team of agents, multiple vehicles, and perhaps aerial assistance,’ ... our cases suggest that such visual observation is constitutionally permissible. It may be that achieving the same result through electronic means, without an accompanying trespass, is an unconstitutional invasion of privacy, but the present case does not require us to answer that question.”

The fourth amendment is supposed to address invasive and inconvenient general warrants and search warrants. And that’s “inconvenient” from the point of view of the person being investigated. I don’t understand the view that all’s fair as long as the police do a certain amount of busywork, but that does seem to be popular even among some judges.