Launch of the OpenAQ Comparison Tool!

3 min readNov 1, 2021


OpenAQ has launched an enhanced version of the comparison tool that provides a simple way to compare data across both reference grade monitors and low cost sensors. The goals of the tool are to:

  • Enhance the OpenAQ platform by providing OpenAQ Community members with a tool to spatially select and compare different air pollution measurements across the platform
  • Provide a more comprehensive view of air quality trends and patterns
  • Expand community understanding of air pollution and broaden their spatial understanding of air quality trends
  • Provide additional use cases that utilize both reference grade and low cost data

A few ways that OpenAQ community members can utilize this tool include:

  • Compare air quality data between low-cost sensors and reference grade monitors
  • Identify areas where there may be data gaps
  • Compare sensor performance with nearby sensors

How to use the Comparison Tool

Navigate to the OpenAQ Website. Click on the “Open Data” pulldown menu at the top, then click on the “World Map Button”. The world map will display all of the reference grade monitors and low cost sensors hosted on the OpenAQ platform, totaling over 30,000 measurement devices.

Reference grade monitors are symbolized as circles and low-cost sensors are symbolized as squares. The user can zoom in to their region of the world and start using the tool by clicking on a reference grade monitor or a low-cost sensor of interest. OpenAQ Community members can compare up to three monitors at a time with any combination of low-cost sensors and/or reference grade monitors. Click the “compare” button.

The user can click on the hyperlink to the monitor to see the number of measurements collected by that specific monitor, how long the monitor has been collecting measurements, what pollutants are being collected, and a scatter plot showing the concentrations of the pollutant specific over time.

Next to the first sensor selected, is a button, which will allow the user query available monitors by country, city/region, and location. The Compare page will show a scatter plot of concentrations for each of the monitors selected.

The new features of the compare tool allow the user to take the existing sensor and, using the map, can list all the nearby sensors (line of sight distance calculation) and how recently they were updated

Once you add a monitor to compare to your originally selected monitor, the features of the newly selected sensor or monitor will show up to the right of the original sensor. After two monitors are selected and added to the compare tool, data from both of them will be presented on a scatterplot showing concentration of the selected pollutant over time (typically the last seven days). OpenAQ Community members will be able to visually assess how related the sensor is to the originally selected monitor or sensor with a single scatter plot displaying both selected monitors.

Sample Statistics

The updated comparison tool includes sample statistics — count, mean, median, mode, and range of air quality. The tool also includes a best fit line by least squares to show how closely related the data is. Finally, the tool also includes correlation factors (r and R2). A R2 indicates performance of the low cost sensor, and how correlated the data is with the initial monitor selected. The higher the R2 value, the more closely correlated the data is.

The tool is always changing, and we want this guide to be evergreen. How will you be using our tool? Share with us on OpenAQ Slack!




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