The Automated Surface Observing System (ASOS) automatically collects weather data and provides accurate, 24-hour accumulated weather reports to local weather observers; weather forecasters; airport personnel, including pilots and air traffic controllers (ATC's); and Federal Aviation Administration (FAA) and National Weather Service (NWS) personnel. ASOS functions include: measurement of weather elements, data processing and display, communication, and data storage (archiving). The ASOS is a flexible system with a modular construction that allows deployment in a variety of configurations for operation with or without the attendance of an observer. Unattended, the ASOS automatically collects, process, and error checks data and formats, displays, archives, and reports the weather elements included in a surface weather observation. The ASOS also accepts imputs from observers (when present), who may also override or add information to the automatically generated observation. Because of the flexibility of the ASOS, it can provide useful weather information in text, video, and audio format to a variety of users. Table 1.1.1 lists the users with which the ASOS can interface.