SpotFlight: Planes Overhead

Hold your phone up to the sky and the aircraft overhead appear on the camera image where they actually are: callsign, altitude, distance, the cities they left and are heading for. Not a map to translate into the world around you, but the real airplane, in the direction you are looking.

AIM — augmented reality • Up to 40 target circles over the live camera, colour-coded for aircraft above the horizon, aircraft hidden behind the Earth's curve, and emergency squawks. • Non-overlapping labels: callsign, distance, altitude, climb or descent, type, route cities. • Tap for a full card, or track one flight and hide the rest. • Drag to correct the compass. The labels follow your finger onto the aircraft you can see.

MAP • Traffic on its real heading, plus the camera's field of view as a cone: point that way, this is what you catch. • Range 50, 100 or 200 km. Search by city in your own spelling: Londres finds London, Alger finds Algiers.

NEARBY • Everything in range, nearest first: bearing, elevation, altitude, speed, vertical rate — with a badge on rows that are below the horizon, barometric, or extrapolated.

SEARCH • By flight number (AF498), callsign (AFR498), registration (F-GKXA) or ICAO address. • A warning when an airline uses dynamic callsigns unrelated to your ticket.

CLOSE-PASS ALERTS • A banner and a notification before an aircraft passes close overhead: distance, countdown, where to look. • Threshold 3 to 50 km, warning 30 s to 5 min. Passes below the horizon never fire, so distant landings stay quiet.

SUN AND MOON TRANSITS

From your exact position, the app predicts when an aircraft will cross the disc of the Sun or the Moon, up to five minutes ahead, with where to look and how long it lasts. Not long: an airliner takes about one second to cross the Sun. Nobody catches that without warning.

The astronomy is not approximate: solar and lunar positions were checked against the JPL DE421 ephemeris, 28 arcseconds of error at worst for the Sun, 46 for the Moon. The Moon is computed for where you stand, not the centre of the Earth — nearly a degree, twice its own width.

Never look directly at the Sun, with or without a phone in front of you. Frame it on the screen and watch the screen.

FREE

No subscription, no in-app purchase, no account, no analytics, no tracking. Your first 24 hours are open; after that a rewarded video you start yourself unlocks the AR view and transits for another 24 hours. Map, list, search and alerts stay free; no ad is ever shown on its own. Your coordinates go to the public aircraft feed — that is the question being asked.

THE GEODESY

Nothing in the picture is recognized; it is all geometry. WGS84 and Vincenty's formulae throughout, positions carried through Earth-centered coordinates into a local horizon frame, so curvature is exact rather than corrected for. Dead reckoning corrects two delays that add up: the age of a position when the feed answered, and the time since. 295 unit tests cover the math.

WHAT IT CANNOT DO

• Requires an internet connection; no offline mode. • Coverage comes from volunteer receivers: strong over Europe and North America, thin over oceans and open country. Military and many private aircraft broadcast nothing usable. • Origin and destination are not in ADS-B. They come from another database and are missing for about a quarter of flights. • Predictions assume constant heading, speed and climb rate; an aircraft that turns cancels its own. • The compass is the limit, not the math: 5 to 15 degrees of error. Hence drag-to-correct. • iPhone, portrait only. Six languages; units metric, imperial or aviation, automatic or your choice. For enjoyment, never for navigation.

DATA

Live aircraft positions contain information from adsb.lol, made available under the Open Database License (ODbL). Route information is provided by adsbdb.com; the route data is the work of David Taylor, Edinburgh and Jim Mason, Glasgow. Provided as is, with no warranty of accuracy or availability.