the form of specific headings, based on the use of radar). ATC will use an imaginary "approach gate" when vectoring aircraft to the final approach course. This gate will be 1 nautical mile (NM) from the FAF and at least 5 NM from the landing threshold. Outside radar environments, the instrument approach starts at the IAF. Types of approaches Though ground-based NAVAID approaches still exist, the FAA is transitioning to approaches which are satellite-based (RNAV). Additionally, in lieu of the published approach procedure, a flight may continue as an IFR flight to landing while increasing the efficiency of the arrival with either a contact or visual approach. Visual approach A visual approach is an ATC authorization for an aircraft on an IFR flight plan to proceed visually to the airport of intended landing; it is not an instrument approach procedure. A visual approach may be requested by the pilot or offered by ATC. Visual approaches are possible when weather conditions permit continuous visual contact with the destination airport. They are issued in such weather conditions in order to expedite handling of IFR traffic. The ceiling must be reported or expected to be at least 1000 feet AGL (above ground level) and the visibility is at least 3 SM (statute miles). A pilot may accept a visual approach clearance as soon as the pilot has the destination airport in sight. According to ICAO Doc. 4444, it is enough for a pilot to see the terrain to accept a visual approach. The point is that if a pilot is familiar with the terrain in the vicinity of the airfield he/she may easily find the way to the airport having the surface in sight. ATC must ensure that weather conditions at the airport are above certain minima (in the U.S., a ceiling of 1000 feet AGL or greater and visibility of at least 3 statute miles) before issuing the clearance. According to ICAO Doc. 4444, it is enough if the pilot reports that in his/her opinion the weather conditions allow a visual approach to be made. In general, the ATC gives the information about the weather but it's the pilot who makes a decision if the weather is suitable for landing. Once the pilot has accepted the clearance, he/she assumes responsibility for separation and wake turbulence avoidance and may navigate as necessary to complete the approach visually. According to ICAO Doc. 4444, ATC