Sky Score: noise and liveability map

What this is: DEFRA Strategic Noise Map (Round 4, published 2022), the long-term average aircraft noise around LHR, LCY and LGW - modelled from a year of actual flight tracks, not a live feed. That year is 2021, when COVID restrictions held air traffic far below normal, and Heathrow's Noise Action Plan says the 2021 results show a highly anomalous situation. Measured, they understate it by about half: Heathrow's 55 dB contour on this 2021 map covers 75.6 km², and the CAA's model of 2025, a year with as many Heathrow flights as 2019, covers 142.4 km². Both are the CAA's model, run on different years, so read that as an order of magnitude, not a correction. Round 4 is still the latest official round; the Environmental Noise Directive requires mapping every five years, so Round 5 falls due in 2027; DEFRA has not published a date. Used by councils for planning decisions. The overlay shows DEFRA's modelled contours; a postcode search gives a 0-10 quiet score for that location, not a decibel reading. All levels are outdoor, at the building's facade: indoors, with the windows shut, it is quieter, though gardens, balconies and open windows are not.

What this is: how many planes pass overhead at each postcode on each kind of day (the wind decides which way an airport flies), from the busiest airport over it, counted from community flight tracking and checked against the CAA's monthly totals, over the months counted. Where two airports' planes cross one postcode it shows the busier one's count: the two are never added, because each airport's kinds of day are its own. Only the airports whose counts passed that check are counted; helicopters and small airfields are not. Each postcode keeps its own figure: nothing is averaged over an area. District lines are drawn faintly; every district's postcodes are on its planes overhead page.