Seatback flight map vs your phone’s GPS

Where the seatback map gets its data

The moving map on an inflight entertainment screen is fed by the aircraft. Position, altitude, ground speed and time to destination come from the avionics, the same navigation systems the crew fly with, and the map software draws them over a stored world map.

Two companies supply much of what passengers see. Panasonic Avionics’ Arc map runs at more than 40 airlines on over 1,300 aircraft, and FlightPath3D is used by more than 70 airlines. Both can show the map on the seatback screen and on your own phone or laptop through the aircraft’s wireless portal.

Because the data is the aircraft’s own, the figures on a seatback map are the ones to trust when the two disagree. The map knows the planned destination and the flight’s schedule, which your phone does not.

Passengers use these maps a great deal. FlightPath3D says passengers spend an average of 55 minutes per flight on its seatback map and 18 minutes on its mobile map, which gives a sense of how many people want to know where they are.

How accurate your phone’s GPS is in a cabin

GPS.gov puts typical smartphone accuracy at about 4.9 metres under open sky. A cabin is not open sky. The fuselage is metal and blocks much of the signal, so the phone relies on what comes through the windows. In a window seat that is usually plenty for a steady fix. In a middle or aisle seat the fix can take longer and the reported accuracy is worse.

Even a poor fix is far better than you need at cruise. An error of fifty metres does not change which town you are over. Where the phone falls short is the first fix after boarding: with no mobile data there is no assisted GPS, so a cold start can take a couple of minutes.

The reported accuracy also moves around during the flight. As the aircraft turns, your window faces a different part of the sky and different satellites come into view. Holding the phone close to the window, rather than on the tray table, gives the receiver the best chance.

Phone GPS, open sky

About 4.9 m

Phone GPS, in cabin

Worse, varies by seat

Why the altitude figures often differ

Put a phone next to a seatback map and the altitudes rarely match exactly. The aircraft reports the altitude its instruments use, which at cruise is based on a standard air pressure setting rather than true height above sea level. Your phone reports a height worked out geometrically from satellites.

Neither is broken. They measure different things, and the gap changes with the weather. Ground speed usually agrees closely, because both are measuring movement over the ground.

That ground speed includes the wind. A strong tailwind at cruise can push it well above the aircraft’s speed through the air, and a headwind pulls it down, which is why the same route can take noticeably different times in each direction. Time remaining on any map moves with it.

Many aircraft have no moving map

A seatback map needs a seatback screen, and a large share of short-haul flying has none. Low-cost narrowbodies are usually bare: Ryanair, easyJet, Jet2 and Frontier fly without screens, and American removed them from its whole domestic narrowbody fleet. On those aircraft there is no moving map to look at, whatever you are willing to pay.

Even where a screen exists, the map is one channel among films and menus, and a faulty screen stays faulty for the whole flight.

If you want to know in advance, check the aircraft type on your booking and look at the airline’s own cabin or fleet pages. Airlines that fit screens usually say so, because it is a selling point. If nothing is mentioned on a short-haul narrowbody, assume there is no map.

Long-haul widebodies are far more likely to have screens. American, for example, keeps them on its 777 and 787 fleets while its domestic narrowbodies fly without.

Portal maps need the aircraft wifi

Arc and FlightPath3D can both appear on your own device, but only when you connect to the aircraft’s wireless network and open its portal. That is a local network on board, and the aircraft has to carry the system in the first place.

It also means the map is only there while you are connected, and it stops when the portal is switched off. Your phone’s GPS has no such dependency: it works in Airplane Mode with every radio off.

Joining the portal means switching your phone’s wifi back on. Airlines generally allow that in flight, but follow the crew’s instructions on when devices can be used.

What a phone cannot know

A phone app only knows what your GPS tells it and what you tell it. It does not receive the flight plan, the schedule, the gate or any airline announcement. It does not see other aircraft, because there is no receiver for them in your phone.

That makes the phone good at the physical facts of the flight: where you are, how high, how fast and in which direction. It is poor at anything that depends on the airline, such as a delay or a change of arrival gate. For those, the crew and the seatback screen remain the better sources.

A phone also cannot tell you the seatback map is wrong. If the two disagree about your position by more than a little, trust the aircraft; your phone probably has a poor fix.

Using both on the same flight

If your seat has a working map, use it. It has the better data, and it costs nothing to glance at. Keep a phone app for the flights that do not, and for the parts the screen does not do.

SkyDot is one such app. You download a regional map pack before you fly and start tracking when you board. It reads your phone’s GPS and shows altitude, ground speed, heading, the town or sea below and a route line to your destination, then saves the flight to a travel log when it detects the landing. Its time remaining is calculated from your ground speed and the distance left, not from the airline’s schedule, so treat it as an estimate.

A simple habit works well on fitted aircraft: glance at the seatback screen for the airline’s arrival time, and let the phone keep the record.