How Air Quality Is Measured and Mapped
Separate monitor concentrations, satellite products, chemical forecasts and health indexes before interpreting a colored air-quality map.
Explore the air-quality mapWhat the data really means
Use these four anchors before interpreting the related live visualization.
- Ground monitor
- Measures pollutant concentration at one site
- Satellite product
- Observes atmospheric properties from orbit
- Forecast model
- Calculates a gridded future atmosphere
- AQI
- Communicates health context from pollutant-specific rules
A monitor samples air at a particular place
Regulatory and research stations draw ambient air through instruments designed for specific pollutants. Networks can measure fine and coarse particulate matter, ozone, nitrogen dioxide, sulfur dioxide, carbon monoxide and other compounds. Each value belongs to a station, instrument method, averaging period, unit and timestamp.
One station cannot describe every street or elevation around it. Nearby traffic, terrain, wind, atmospheric mixing and emission sources create real spatial differences, while maintenance and quality-control status affect whether a reading is suitable for public use.
Concentration and AQI are not the same value
A pollutant concentration is a physical measurement in units such as micrograms per cubic metre or parts per billion. An air-quality index converts a pollutant-specific concentration and averaging period into a communication scale tied to health guidance. The highest relevant sub-index commonly determines the reported overall category.
Index systems and thresholds vary by jurisdiction. A value labeled US AQI should not be silently compared with a European or national index as if the numbers were interchangeable. PlanetVexa retains the index or concentration label supplied by the source.
Satellites and models fill different gaps
Satellites observe radiation influenced by gases, aerosols, clouds and the surface. Many products describe a total atmospheric column or a retrieved property, not a direct breathing-level concentration. Chemical transport models combine emissions, weather and atmospheric chemistry to estimate three-dimensional pollutant fields and forecasts.
Ground monitors provide local observations; satellite products provide broad remote-sensing coverage; models provide continuous grids and future valid times. Combining them is powerful only when observation, retrieval and forecast remain visibly distinct.
A smooth map can hide uncertainty
Interpolated or modeled color fields look continuous even where no monitor exists. Resolution, cloud screening, emissions inventories, boundary conditions and model initialization all affect the result. A map valid time can also differ from the newest ground observation time.
PlanetVexa identifies the source, pollutant, unit, model run or observation time and freshness. The display is environmental context, not medical advice; official local guidance remains the correct source for health actions.
Questions people ask
Is AQI a pollutant concentration?
No. It is a communication index calculated from pollutant-specific concentrations, averaging periods and breakpoints.
Does a colored model cell mean a monitor measured that value?
No. A model cell is calculated for an area and valid time; monitor observations are separate point measurements.
Can satellite imagery directly measure the air I breathe?
Not usually. Many satellite products observe an atmospheric column or derived property and require models or other information to estimate surface conditions.
Read the official material
PlanetVexa summarizes these sources in original language and links to the responsible institutions for definitions and operational context.