The ReferenceMonitor Object

Choosing a Reference Data Source

sensortoolkit allows users to work with reference data from one of four potential sources:

  • Local: Reference datasets that are acquired locally from an air monitoring agency overseeing the site at which sensor are collocated alongside reference instrumentation. These data files should be located on the user’s computer.

  • AQS: EPA’s Air Quality System is the primary repository for acquiring reference datasets for monitors located at monitoring sites managed by state, local, tribal, and federal agencies. Datasets in AQS undergo rigorous quality control / quality assurance measures and this process may take up to 6 months. In turn, AQS does not contain real-time air quality data. Data are acquired via the sensortoolkit.ReferenceMonitor.query_aqs() method.

  • AirNow: AirNow provides real-time air quality data (up to the most recent hour or day) from monitors managed by state, tribal, local, and federal agencies. Data from this service have not been validated and verified in the same manner as AQS data and should be considered preliminary. Official regulatory monitoring data are available from AQS. Data are acquired via the sensortoolkit.ReferenceMonitor.query_airnow() method.

  • AirNow-Tech: AirNow-Tech provides access to a greater pool of parameter data streams (including a wide range of meteorological parameters) and provides in-browser tools for visualizing and analyzing reference datasets. Unlike the AQS or AirNow API services, reference data from AirNow-Tech must be manually downloaded to the user’s computer from the AirNow-Tech website prior to use with sensortoolkit.

If users are not acquiring reference data locally, users should carefully consider which reference data service (AQS, AirNow, or AirNow-Tech) is appropriate for their intended use. The list of valid query parameters for reference measurements varies across services. The table below shows a list of SDFS parameters alongside an indication of whether each reference data service provides data for each parameter.

Warning

Meteorological parameters including temperature and relative humidity are not available from the AirNow API.

Numerous sensortoolkit methods including plotting functions and summary statistics require the availability of meteorological data (temperature and relative humidity). These methods are used by SensorEvaluation and PerformanceReport to indicate meteorological conditions at the testing site and meteorological influences on parameter measurements.

If users choose to make use of the AirNow API for acquiring reference data, please note that functionality will be limited for methods requiring the use of meteorological datasets.

Table of Reference Sources and Parameters

Parameter Name
(Data Acquisition Method)

AirNow API
(API Query)

AQS API
(API Query)

AirNow-Tech
(Manual Download)

\(PM_{1}\) (particulate matter < 1
micrometer in aerosol diameter)

Not Available

Not Available

Not Available

\(PM_{2.5}\) (particulate matter < 2.5
micrometers in aerosol diameter)

Valid

Valid

Valid

\(PM_{10}\) (particulate matter < 10
micrometers in aerosol diameter)

Valid

Valid

Valid

\(O_{3}\) (Ozone)

Valid

Valid

Valid

\(NO\) (Nitric Oxide)

Not Available

Valid

Valid

\(NO_{2}\) (Nitrogen Dioxide)

Valid

Valid

Valid

\(NO_{x}\) (Nitrogen Oxides)

Not Available

Valid

Valid

\(SO_{2}\) (Sulfur Dioxide)

Valid

Valid

Valid

\(SO_{x}\) (Sulfur Dioxides)

Not Available

Not Available

Not Available

\(CO\) (Carbon Monoxide)

Valid

Valid

Valid

Relative Humidity

Not Available

Valid

Valid

Temperature

Not Available

Valid

Valid

Dew point

Not Available

Valid

Valid

Wind Speed

Not Available

Valid

Valid

Wind Direction

Not Available

Valid

Valid

Pressure

Not Available

Valid

Valid