Custom AirNow Maps - Changing the Monitor and Contour Layers

If you want to select specific layers of the map, like PM10 monitors or the Ozone contour, this is also done with URL variables.

You can use the mlayer variable to add Monitors, with the following values:

  • Ozone and PM—mlayer=ozonepm
  • Ozone—mlayer=ozone
  • PM (2.5 and 10)—mlayer=pm
  • PM2.5–mlayer=pm25
  • PM10–mlayer=pm10
  • No Monitors—mlayer=none
Monitor and Contour layers
Fig: AirNow Map Showing Default Contours (Layer Selected for Ozone, PM 2.5, and PM 10)

Note that only one monitor layer can be on at a time, so turning the Ozone layer on automatically turned off the default Ozone and PM layer.

For example, this is how you would enable ozone monitors on the standard map: https://gispub.epa.gov/airnow/index.html?mlayer=ozone.

Note that only one monitor layer can be on at a time, so turning the Ozone layer on automatically turned off the default Ozone and PM layer.

Also note that this map is an example of choices which will end up confusing the user. The ozone sensors are selected and it’s a pretty good ozone day so they’re almost all green. Unfortunately, the Ozone and PM contours are still on, and what’s driving the AQI (mostly yellow) is PM. This map even has areas that are orange with a bunch of green sensors in them. Sophisticated users will likely figure this out quickly, but casual users will likely just assume something is broken.

In short, make sure your custom map doesn’t do this! And make sure that, if the defaults don’t make sense for you map, you go ahead and turn them off (in this case using clayer=none, explained next).

The same methodology applies to contours. In this case you use the clayer variable in the URL.

  • Ozone and PM (PM 2.5 and PM 10)—clayer=ozonepm
  • Ozone—clayer=ozone
  • PM2.5 – clayer=pm25
  • No Monitors—clayer=none

For example, this is how you would enable PM2.5 contours on the standard map: https://gispub.epa.gov/airnow/index.html?clayer=pm25.

Note that only one monitor layer can be on at a time, so turning the Ozone layer on automatically turned off the default Ozone and PM layer.
Fig: AirNow Map Showing Contours with Layer Selected for Just PM 2.5

Note that only one monitor layer can be on at a time, so turning the Ozone layer on automatically turned off the default Ozone and PM layer.