What is the definition of “airport boundary”? While flying in to KBTR in a helicopter, I called tower and stated “10 west, landing south ramp with information Mike”. They responded “proceed to the airport boundary”. When I was closer I got the landing clearance to the ramp. Does the phraseology “airport boundary” have a specific meaning, or is it simply in lieu of a pattern entry instruction. My local controllers typically give a reporting instruction like “continue inbound, report 1 west”
It's effectively a reporting point consisting of the point at which the controller expects you to cross the perimeter fence line around the airport property.  If the controller uses that term, I would expect that there is a pretty obvious perimeter fence, and the controller isn't too concerned with the precise location at which you cross it, within reason.