Aerodromes are defined as either public or private use. Public use aerodromes do not require prior permission to use. Private use either require Prior Permission Required (PPR), such as military aerodromes for civilian aircraft, or Prior Notice Required (PNR). In the event of emergency or distress situations both PPR and PNR requirements are removed.  Aerodromes may be registered, which means that information about these facilities will be published in  documents such as the Canada Flight Supplement (CFS). Certification is another level of standards that  applies particularly to aerodromes within built-up areas, or where scheduled passenger carrying services are provided. Very few aerodromes operate as certified airports.  Runways are the surfaces used for takeoffs and landings, and taxiways are surfaces the aircraft moves on to get to the runway. Runways and taxiways are known as the manoeuvring area, and the apron is the area intended for loading and unloading of aircraft. All of the area of the aerodrome where the aircraft move, including the manoeuvring area and the apron is called the movement area. Wind indicators such as windsocks are coloured international orange and white at licensed airports and solid orange at unlicenced aerodromes. Perimeter markers for runways follow the same colour scheme.