The needs of airports may vary depending on the types of operations typically conducted at the airport, as well as the type of weather common to the airport. The TRB Airport Cooperative Research Program's ACRP Synthesis 105: Airport Surface Weather Observation Options for General Aviation Airports aims to provide the operators of general aviation (GA) airports a comprehensive source of information about airport-based weather observation options so they may make informed decisions to support the specific operational needs of their airport. Weather observations at airports can come from either FAA-approved (certified) or advisory (non-certified) sources. Weather reporting at a GA airport, whether certified or not, typically comes from automated sources, as human observers are increasingly being phased out or are stationed mainly at commercial service airports.