delivered the opinion of the Court.
We granted certiorari to determine whether the Fourth Amendment is violated by aerial observation without a warrant from an altitude of 1,000 feet of a fenced-in backyard within the curtilage of a home.
I
On September 2, 1982, Santa Clara Police received an anonymous telephone tip that marijuana was growing in respondent’s backyard. Police were unable to observe the contents of respondent’s yard from ground level because of a 6-foot outer fence and a 10-foot inner fence completely enclosing the yard. Later that day, Officer Shutz, who was assigned to investigate, secured a private plane and flew over respondent’s house at an altitude of 1,000 feet, within navigable airspace; he was accompanied by Officer Rodriguez. Both officers were trained in marijuana identification. From the overflight, the officers readily identified marijuana plants 8 feet to 10 feet in height growing in a 15- by 25-foot plot in respondent’s yard; they photographed the area with a standard 35mm camera.
On September 8, 1982, Officer Shutz obtained a search warrant on the basis of an affidavit describing the anonymous tip and their observations; a photograph depicting respondent’s house, the backyard, and neighboring homes was attached to the affidavit as an exhibit. The warrant was *210executed the next day and 73 plants were seized; it is not disputed that these were marijuana.
After the trial court denied respondent’s motion to suppress the evidence of the search, respondent pleaded guilty to a charge of cultivation of marijuana. The California Court of Appeal reversed, however, on the ground that the warrantless aerial observation of respondent’s yard which led to the issuance of the warrant violated the Fourth Amendment. 161 Cal. App. 3d 1081, 208 Cal. Rptr. 93 (1984). That court held first that respondent’s backyard marijuana garden was within the “curtilage” of his home, under Oliver v. United States, 466 U. S. 170 (1984). The court emphasized that the height and existence of the two fences constituted “objective criteria from which we may conclude he manifested a reasonable expectation of privacy by any standard.” 161 Cal. App. 3d, at 1089, 208 Cal. Rptr., at 97.
Examining the particular method of surveillance undertaken, the court then found it “significant” that the flyover “was not the result of a routine patrol conducted for any other legitimate law enforcement or public safety objective, but was undertaken for the specific purpose of observing this particular enclosure within [respondent’s] curtilage.” Ibid. It held this focused observation was “a direct and unauthorized intrusion into the sanctity of the home” which violated respondent’s reasonable expectation of privacy. Id., at 1089-1090, 208 Cal. Rptr., at 98 (footnote omitted). The California Supreme Court denied the State’s petition for review.
We granted the State’s petition for certiorari, 471 U. S. 1134 (1985). We reverse.
The State argues that respondent has “knowingly exposed” his backyard to aerial observation, because all that was seen was visible to the naked eye from any aircraft flying overhead. The State analogizes its mode of observation to a knothole or opening in a fence: if there is an opening, the police may look.
*211The California Court of Appeal, as we noted earlier, accepted the analysis that unlike the casual observation of a private person flying overhead, this flight was focused specifically on a small suburban yard, and was not the result of any routine patrol overflight. Respondent contends he has done all that can reasonably be expected to tell the world he wishes to maintain the privacy of his garden within the curtilage without covering his yard. Such covering, he argues, would defeat its purpose as an outside living area; he asserts he has not “knowingly” exposed himself to aerial views.
II
The touchstone of Fourth Amendment analysis is whether a person has a “constitutionally protected reasonable expectation of privacy.” Katz v. United States, 389 U. S. 347, 360 (1967) (Harlan, J., concurring). Katz posits a two-part inquiry: first, has the individual manifested a subjective expectation of privacy in the object of the challenged search? Second, is society willing to recognize that expectation as reasonable? See Smith v. Maryland, 442 U. S. 735, 740 (1979).
Clearly — and understandably — respondent has met the test of manifesting his own subjective intent and desire to maintain privacy as to his unlawful agricultural pursuits. However, we need not address that issue, for the State has not challenged the finding of the California Court of Appeal that respondent had such an expectation. It can reasonably be assumed that the 10-foot fence was placed to conceal the marijuana crop from at least street-level views. So far as the normal sidewalk traffic was concerned, this fence served that purpose, because respondent “took normal precautions to maintain his privacy.” Rawlings v. Kentucky, 448 U. S. 98, 105 (1980).
Yet a 10-foot fence might not shield these plants from the eyes of a citizen or a policeman perched on the top of a truck or a two-level bus. Whether respondent therefore manifested *212a subjective expectation of privacy from all observations of his backyard, or whether instead he manifested merely a hope that no one would observe his unlawful gardening pursuits, is not entirely clear in these circumstances. Respondent appears to challenge the authority of government to observe his activity from any vantage point or place if the viewing is motivated by a law enforcement purpose, and not the result of a casual, accidental observation.
We turn, therefore, to the second inquiry under Katz, i. e., whether that expectation is reasonable. In pursuing this inquiry, we must keep in mind that “[t]he test of legitimacy is not whether the individual chooses to conceal assertedly ‘private’ activity,” but instead “whether the government’s intrusion infringes upon the personal and societal values protected by the Fourth Amendment.” Oliver, supra, at 181-183.
Respondent argues that because his yard was in the curtilage of his home, no governmental aerial observation is permissible under the Fourth Amendment without a warrant.1 The history and genesis of the curtilage doctrine are instructive. “At common law, the curtilage is the area to which extends the intimate activity associated with the ‘sanctity of a man’s home and the privacies of life.’” Oliver, supra, at 180 (quoting Boyd v. United States, 116 U. S. 616, 630 (1886)). See 4 Blackstone, Commentaries *225. The *213protection afforded the curtilage is essentially a protection of families and personal privacy in an area intimately linked to the home, both physically and psychologically, where privacy expectations are most heightened. The claimed area here was immediately adjacent to a suburban home, surrounded by high double fences. This close nexus to the home would appear to encompass this small area within the curtilage. Accepting, as the State does, that this yard and its crop fall within the curtilage, the question remains whether naked-eye observation of the curtilage by police from an aircraft lawfully operating at an altitude of 1,000 feet violates an expectation of privacy that is reasonable.
That the area is within the curtilage does not itself bar all police observation. The Fourth Amendment protection of the home has never been extended to require law enforcement officers to shield their eyes when passing by a home on public thoroughfares. Nor does the mere fact that an individual has taken measures to restrict some views of his activities preclude an officer’s observations from a public vantage point where he has a right to be and which renders the activities clearly visible. E. g., United States v. Knotts, 460 U. S. 276, 282 (1983). “What a person knowingly exposes to the public, even in his own home or office, is not a subject of Fourth Amendment protection.” Katz, supra, at 351.
The observations by Officers Shutz and Rodriguez in this case took place within public navigable airspace, see 49 U. S. C. App. §1304, in a physically nonintrusive manner; from this point they were able to observe plants readily discernible to the naked eye as marijuana. That the observation from aircraft was directed at identifying the plants and the officers were trained to recognize marijuana is irrelevant. Such observation is precisely what a judicial officer needs to provide a basis for a warrant. Any member of the public flying in this airspace who glanced down could have seen *214everything that these officers observed. On this record, we readily conclude that respondent’s expectation that his garden was protected from such observation is unreasonable and is not an expectation that society is prepared to honor.2
The dissent contends that the Court ignores Justice Harlan’s warning in his concurrence in Katz v. United States, 389 U. S., at 361-362, that the Fourth Amendment should not be limited to proscribing only physical intrusions onto private property. Post, at 215-216. But Justice Harlan’s observations about future electronic developments and the potential for electronic interference with private communications, see Katz, supra, at 362, were plainly not aimed at simple visual observations from a public place. Indeed, since Katz the Court has required warrants for electronic surveillance aimed at intercepting private conversations. See United States v. United States District Court, 407 U. S. 297 (1972).
Justice Harlan made it crystal clear that he was resting on the reality that one who enters a telephone booth is entitled to assume that his conversation. is not being intercepted. This does not translate readily into a rule of constitutional dimensions that one who grows illicit drugs in his backyard is “entitled to assume” his unlawful conduct will not be ob*215served by a passing aircraft — or by a power company repair mechanic on a pole overlooking the yard. As Justice Harlan emphasized,
“a man’s home is, for most purposes, a place where he expects privacy, but objects, activities, or statements that he exposes to the ‘plain view’ of outsiders are not ‘protected’ because no intention to keep them to himself has been exhibited. On the other hand, conversations in the open would not be protected against being overheard, for the expectation of privacy under the circumstances would be unreasonable.” Katz, supra, at 361.
One can reasonably doubt that in 1967 Justice Harlan considered an aircraft within the category of future “electronic” developments that could stealthily intrude upon an individual’s privacy. In an age where private and commercial flight in the public airways is routine, it is unreasonable for respondent to expect that his marijuana plants were constitutionally protected from being observed with the naked eye from an altitude of 1,000 feet. The Fourth Amendment simply does not require the police traveling in the public airways at this altitude to obtain a warrant in order to observe what is visible to the naked eye.3
Reversed.
Because the parties framed the issue in the California courts below and in this Court as concerning only the reasonableness of aerial observation generally, see Pet. for Cert, i, without raising any distinct issue as to the photograph attached as an exhibit to the affidavit in support of the search warrant, our analysis is similarly circumscribed. It was the officer’s observation, not the photograph, that supported the warrant. Officer Shutz testified that the photograph did not identify the marijuana as such because it failed to reveal a “true representation” of the color of the plants: “you have to see it with the naked eye.” App. 36.
The California Court of Appeal recognized that police have the right to use navigable airspace, but made a pointed distinction between police aircraft focusing on a particular home and police aircraft engaged in a “routine patrol.” It concluded that the officers’ “focused” observations violated respondent’s reasonable expectations of privacy. In short, that court concluded that a regular police patrol plane identifying respondent’s marijuana would lead to a different result. Whether this is a rational distinction is hardly relevant, although we find difficulty understanding exactly how respondent’s expectations of privacy from aerial observation might differ when two airplanes pass overhead at identical altitudes, simply for different purposes. We are cited to no authority for this novel analysis or the conclusion it begat. The fact that a ground-level observation by police “focused” on a particular place is not different from a “focused” aerial observation under the Fourth Amendment.
In Dow Chemical Co. v. United States, post, p. 227, decided today, we hold that the use of an aerial mapping camera to photograph an industrial manufacturing complex from navigable airspace similarly does not require a warrant under the Fourth Amendment. The State acknowledges that “[ajerial observation of curtilage may become invasive, either due to physical intrusiveness or through modern technology which discloses to the senses those intimate associations, objects or activities otherwise imperceptible to police or fellow citizens.” Brief for Petitioner 14-15.