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openaq-data-format

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

FieldTypeRequiredDescriptionExample
parameterStringThe measured parameter; acceptable values are pm25, pm10, co, bc, so2, no2, o3"pm25"
locationStringUnique location name of the station"Escuela E-10"
cityStringCity (or regional approximation) containing location"Tocopilla"
countryStringCountry containing location in two letter ISO format"CL"
valueNumberRecorded value10.2
unitStringUnit of measurement, see note about units below; acceptable values are µg/m³, ppm"µg/m³"
dateObjectTime 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"}
sourceNameStringID to track measurement to source within the platform"Netherlands"
sourceTypeStringThe type of source; acceptable values are: government, research, other"government"
mobileBooleanIndicates whether the measuring station is stationary or mobilefalse
coordinatesObjectLocation of measurement{"latitude": -22.087, "longitude": -70.193253}
attributionArrayData attribution in descending order of prominence[{"name": "TCEQ", "url":"http://www.tceq.state.tx.us"}, {"name": "City of Houston Health Department"}]
averagingPeriodObjectInformation about the time resolution of the measurement{"value": 1, "unit": "hours"}

Formatted Data Object

The formatted data json object should look something like this:

{"date":{"utc":"2020-10-01T00:00:00.000Z","local":"2020-10-01T04:00:00+04:00"},
  "parameter":"pm25","value":20,"unit":"µg/m³",
  "averagingPeriod":{"value":1,"unit":"hours"},
  "location":"US Diplomatic Post: Abu Dhabi","city":"Abu Dhabi","country":"AE",
  "coordinates":{"latitude":24.424399,"longitude":54.433746},
  "attribution":[{"name":"EPA AirNow DOS","url":"http://airnow.gov/index.cfm?action=airnow.global_summary"}],
  "sourceName":"StateAir_AbuDhabi","sourceType":"government","mobile":false}

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:

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.

PollutantPreferred unit
PM 2.5µg/m³
PM 10µg/m³
BCµg/m³
COppm
NO2ppm
SO2ppm
O3ppm

Source types

Measurements can be provided by different types of sources: