Definition
An Automated Surface Observing System (ASOS) is a fully automated weather station operated primarily at major airports to provide continuous, high-resolution atmospheric data. ASOS delivers detailed measurements of temperature, dew point, pressure, wind, visibility, cloud layers, precipitation type, and other critical meteorological conditions.
Usage
Automated Surface Observing System reports give pilots, air traffic controllers, and drone operators a standardized and extremely reliable source of surface weather information. These stations form the backbone of U.S. aviation weather reporting and play a foundational role in producing METAR and SPECI observations.
Relevance to the Industry
Automated Surface Observing System is essential for drone operations because it provides the most accurate, frequently updated surface weather data available. For RPAS missions—especially those near airports, urban areas, or sensitive airspace—ASOS information helps operators:
• Evaluate wind limits and gust factors
• Determine visibility and cloud ceiling restrictions
• Understand precipitation that may affect sensors or flight stability
• Assess humidity and temperature impacts on battery performance
• Confirm barometric pressure for accurate altitude interpretation
Automated Surface Observing System helps drone teams build safer go/no-go decisions and align missions with regulatory expectations.
How Does ASOS (Automated Surface Observing System) Work?
Automated Surface Observing System consists of a network of advanced meteorological sensors installed around airports. These sensors continuously sample environmental conditions and send raw data to a processing unit. The system:
• Performs automated quality control checks
• Converts sensor data into METAR-format reports
• Issues SPECI updates when weather changes rapidly
• Transmits observations via radio, aviation weather servers, and national data centers
Unlike AWOS, ASOS includes enhanced capabilities—such as precipitation discrimination, freezing rain sensors, sophisticated cloud-height detection, and long-range visibility sensors.
Example in Use
A drone operator preparing for a BVLOS utility inspection checks the regional ASOS station and identifies decreasing visibility due to fog. The ASOS update triggers a necessary mission delay, preventing potential operational and regulatory risk.
Frequently Asked Questions About ASOS (Automated Surface Observing System)
How is ASOS different from AWOS?
Automated Surface Observing System is more advanced, federally maintained, and capable of producing official METAR/SPECI reports with expanded sensor coverage.
Does ASOS update more frequently than METARs?
Yes. Although METARs are issued hourly, ASOS sensors update continuously and can trigger SPECI (special) reports when conditions change rapidly.
Do drone pilots need to check ASOS before flying?
It is not mandatory everywhere, but highly recommended—ASOS provides the most accurate surface weather data available.
Related Acronyms to ASOS
AWOS – Automated Weather Observing System
A similar automated system commonly found at smaller airports. AWOS provides real-time wind, visibility, cloud height, and pressure measurements essential for pre-flight drone planning.
METAR – Aviation Routine Weather Report
The standardized hourly weather report issued at airports, often generated from Automated Surface Observing System data. Drone pilots use METARs to assess current conditions such as wind speed, visibility, and cloud layers.
TAFs – Terminal Aerodrome Forecast
Short-range aviation weather forecasts for a 24–30 hour period around an airport. TAFs help drone operators anticipate developing weather that could impact mission timing and safety.
