A Year of Sky

reading a year of sky…

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In the twelve months ending —, at least — aircraft passed within 500 meters of the building — an average of — a day, roughly one every — from first light until past midnight. There was not a single day without one.¹ The busiest day of the year was —, when — crossed overhead.

The reason is geometry: the building sits almost exactly beneath the final approach to Lisbon airport's runway 02. Most aircraft cross between 200 and 300 meters above the rooftops — about — of everything that passes — sinking along a three-degree line they hold for the last ten kilometers, so low that the registration is legible from a balcony.

This page counts aircraft passing within of the building, — change either and the whole story recomposes.

IThe Year

— fewer more

Fig. 1. A year of days, inked by traffic. Hatched days are receiver outages, filled with a trend-based estimate.¹

Fig. 2. Average flights per day, week by week. The red point is the busiest single day of the year; striped weeks contain receiver outages, reconstructed from trend.

In bulk, a year of sky is just figures.
One aircraft at a time, a constellation —
and constellations only show after dark.

—

Watch the year draw itself. Each spark is one real aircraft at its closest point to the rooftop, appearing in the order it actually flew. The bright line slicing the rings is the runway 02 centerline — drawn not by a cartographer, but by the planes.

Now the view turns. Every dot keeps its identity and flies to where you'd see it standing in the street, looking down the corridor: sideways position against height above the rooftops.

The lens. — aircraft packed into one band of air between 200 and 300 meters — the ILS holds them within a few dozen meters of the same line, year after year. This is what "under the approach" means.

IIIThe Night Shift

The corridor keeps office hours, after a fashion: traffic builds from six, holds a steady beat all day, and does not fade until well past midnight. — passes a day come between eleven at night and seven in the morning, and — crossed in the dead hours between two and five over the year. Modeled from distance, height and aircraft type,² the typical crossing reaches — at the window — and on the median day — passes were loud enough to interrupt a sentence.

35whisper 50quiet street 65conversation 80heavy truck

—typical pass, at the window

Fig. 3. Where the typical pass lands on the loudness scale, in A-weighted decibels.

24-hour traffic clock

passes by hour · midnight at the top · night in blue

acoustic load

median single-event peak · modeled

loud events per day

pale ≥ 70 dBA · bright ≥ 80 dBA

IVThe Census

Who flies over
Aircraft		Passes	Share

Beyond the airline regulars, the year's log holds its share of strangers — types that crossed the neighborhood five times or fewer:

And the archive keeps its curiosities, each one a real aircraft on a real date:

And then, every morning around six,
the first one of the day comes in from the south —
and the count begins again.

One rooftop · Lisboa · twelve months of sky

—

aircraft within 500 m of one apartment — counted one by one from open radio data

—

per day

≈250 m

typical height

—

typical peak

—

distinct aircraft

quiet days

Counts are aircraft tracked by volunteer ADS-B receivers — a lower bound on reality, though a close one: the daily figure (~310 within 500 m) is consistent with Lisbon's ~617 daily aircraft movements, the busiest single-runway airport in the world. On — days the upstream feed went dark; those days are hatched in Fig. 1 and rebuilt from same-weekday trends (≈— passes, kept out of every other figure).
Noise is modeled, not measured: a class-typical source level (heavy jet 84 dBA, narrowbody 78, turboprop 72, light 66 at 300 m) decayed with slant distance to the window at 25·log₁₀(d/300). Trust the rankings, not the decimals.
Data © adsb.lol (ODbL), airplanes.live, adsbexchange.com — queried via adsb.exposed. Location is a single rooftop in Campo de Ourique, under the runway 02 approach; ground elevation ~97 m. Data runs through —. Fetch the latest ↻

Raw instruments → open the Operations Console