Monitoring Sites Visualisation: Mean Vs Peak

This is a prototype visualisation of the annual objectives for monitoring sites, enables you to explore the relationship between the pollution around us across the year and the short peaks we sometimes get. It is only suited to examining the relationship between short term exceedances and annual mean exceedances of NO2 and PM10 . This visualisation starts by showing information for all sites in the LAQN but it is likely you’ll want to filter down to a smaller set. You can find more information on how to use this visualisation under Controls, below the graph. Any data recorded since the start of the previous year may be provisional and subject to change. The information is calculated twice daily, so may not reflect the latest data. There is also another visualisation showing Objective Vs Time Graph. Many thanks to Mehdi Khoury, who created this visualisation.

Data visualistion

Site type
Mean vs Peak
Capture rate

Axes to objectives
Local authority


Slider Bar

The slider on the year bar on the bottom enables you to move through the years and see how conditions at sites are changing, e.g some sites no longer exceed for their peak hours but still have a problem with their annual mean. Select All data capture to see progress in the current year.


Click on a dot (or hold down shift and click to select multiple sites) to turn on or off the label to help with visual tracking . The axis cross at the limit values for each objective so that they split the visualisation in to quadrants.

  • Bottom left – site achieves both objectives (dots are green)
  • Bottom right – site fails the annual mean objective (dots are amber)
  • Top left – site fails hourly objective but passes annual mean (dots are amber )
  • Top right – site fails for both annual mean and hourly objective (dots are red)
If you prefer axis at zero then deselect the “Axes to Objectives” tick box at the top by the filters. Hover over a specific dot to get detailed information for that site on that year.

Local Authority

If any of the above 4 filters have been used then the choice of local authorities will have been reduced to just those with sites that match the criteria. A single local authority can be selected by clicking on it, or multiples by holding down the shift key while selecting with the mouse.


This enables you to choose the geographic area you want from any combination of

  • Inner London (criteria)
  • Outer London
  • Outside London (The LAQN includes sites from areas surrounding London itself)

Site type

Not all monitoring sites are in the same type of location. Some are located to directly monitor emissions from specific roads, others are located away from roads to give a background level that the wider area and population is exposed to. This filter can be used to select any combination of types. The many official classification types have been simplified into 3 groups.

  • Background (These represent levels experienced by the general population and provide a baseline to compare roads to. Includes Background and Suburban classifications. At present there are no Rural classified sites within the LAQN)
  • Roadside (Sites positioned along side busy roads. Includes Kerbside (less than 1m from kerb) and Roadside (less then 5m from kerb) classifications
  • Industrial (sites influenced by industrial activity e.g close to waste transfer sites, quarry haul routes etc)
On the graphs the dot size also shows the site type for extra clarity; Large - Industrial, medium-Roadside, small – Background.

Data Capture

This represents the amount of valid data as a percentage of the year. As well as down time for routine maintenance and calibration many other things can result in data loss; power cuts, flooding, lightening strike, and faults from general wear as a result of running sensitive equipment 24 hours a day 365 days a year often in challenging polluted roadside locations.

  • 90%+ This is what is aimed for
  • 75%+ Even if a site achieves less than 90% it can still be reported above 75% as long as the loss does not represent a specific time period, e.g if all of 3 months of winter was lost.
  • All This should be used with caution since it will also show sites where there is insufficient data for the results to be reportable. This is included to allow the progress on the current year to be seen, and to show when sites were operational.
Hovering over any individual dot on the visualisations will give additional information regarding that site for the year, including the actual data capture rate.

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