A description of the data format provided by the OpenAQ platform.
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README.md

openaq-data-format

A description of the data format provided by the OpenAQ Platform.

Field Type Required Description Example
parameter String The measured parameter; acceptable values are pm25, pm10, co, bc, so2, no2, o3 "pm25"
location String Unique location name of the station "Escuela E-10"
city String City (or regional approximation) containing location "Tocopilla"
country String Country containing location in two letter ISO format "CL"
value Number Recorded value 10.2
unit String Unit of measurement, see note about units below; acceptable values are µg/m³, ppm "µg/m³"
date Object Time of measurement including both local time and UTC time. See note about dates. {"utc":"2015-10-26T17:00:00.000Z", "local": "2015-10-26T14:00:00-03:00"}
sourceName String ID to track measurement to source within the platform "Netherlands"
sourceType String The type of source; acceptable values are: government, research, other "government"
mobile Boolean Indicates whether the measuring station is stationary or mobile false
coordinates Object Location of measurement {"latitude": -22.087, "longitude": -70.193253}
attribution Array Data attribution in descending order of prominence [{"name": "TCEQ", "url":"http://www.tceq.state.tx.us"}, {"name": "City of Houston Health Department"}]
averagingPeriod Object Information about the time resolution of the measurement {"value": 1, "unit": "hours"}

Dates and date ranges

Dates are stored as a javascript date containing both the local time and the UTC time.

"date": {
  "utc": "2015-07-16T20:30:00.000Z",
  "local": "2015-07-17T03:30:00.000+07:00"
}

The averages are always backward looking. That means that if a source reports a time range (3 - 4pm), then the latest time is picked (4pm).

Dealing with multiple measurements

It is possible that a station reports several measurements for the same pollutant per time period. When this occurs, the following measurement is stored:

  • the one with the shortest averaging period (1 hour average instead of 24 hour rolling average)
  • the one that reports the value in the pollutant's preferred unit

Preferred Units

OpenAQ only accepts measurements in µg/m³ and ppm. This means that volumetric concentrations reported in ppb are converted to ppm before being stored to the database. We do not convert between volumetric and mass concentrations (µg/m³ <-> ppm) to avoid making assumptions.

The platform also has a preferred unit of measurement per pollutant, but this is not strictly enforced. The Dutch locations, for example, report all their values in µg/m3.

Pollutant Preferred unit
PM 2.5 µg/m³
PM 10 µg/m³
BC µg/m³
CO ppm
NO2 ppm
SO2 ppm
O3 ppm

Source types

Measurements can be provided by different types of sources:

  • government - Sensors that are deployed by or on behalf of governmental bodies.
  • research - Sensors that are deployed by researchers affiliated with universities and/or research organizations.
  • other - Sensors that are deployed by citizen scientists, often low-cost sensors.