# How to determine aircraft altitude and speed, as a passenger?

Is it possible for a passenger to determine the aircraft's altitude and or speed or location using any mobile apps.

Not all airlines have displays with constant info about this. I had tried using Google maps, but it did not work, maybe because there was no internet/wifi on the aircraft.

Any simple method?

• check the GPS on your smartphone – ratchet freak Oct 5 '15 at 14:35
• i did have the GPS turned on, but google maps was not indicating any thing. Maybe it needs a data connection. – Firee Oct 5 '15 at 14:38
• You can't get location without maps, and you can't get those without a data connection unless you have them loaded on the phone - which in turn means a dedicated app to use them. GPS will give you speed and altitude though. Dependant on your phone, you might be able to preload maps. For example, on my Android phones, I can load maps in Google Maps then make them available for offline use but that will depend on phone, OS and version. I've never tried this for the areas of maps needed to track a flight though. YMMV. – Simon Oct 5 '15 at 14:52
• @Firee, yes, Google maps need data connection to download the map tiles. You need either a pure GPS app that will simply show readings from the GPS (e.g. GPS Essentials) or a navigation that uses offline data including several that use the free OpenStreetMap data. – Jan Hudec Oct 5 '15 at 16:53
• I just used a standalone car navigation system. It displays the location on the map, but also in the status page: longitude latitude, speed, heading, and height. Very handy to put a name on lights or lakes below. First time I saw the GPS displaying 799 km/h :-) – mins Oct 5 '15 at 18:07

I always track my flights, so here is my experience:

## App using offline maps

As it has been said, you will need an app which can download maps prior to the flight. I never had a flight with onboard wifi, but I guess, there's usually a data volume constraint, which could make it expensive.

I use Mapfactor Navigator (Android), which is an offline navigation system for cars etc. The maps can be obtained from within the app, the user has the choice between free maps from the OpenStreetMaps project and TomTom maps, which you have to pay. The maps can be downloaded per country, and big maps are subdivided into smaller pieces. For example, the very detailed map for Germany is divided into four parts, together about 0.8GB of data. The entire USA can be downloaded per state, all together 1.7GB.

It's possible to configure several fields at the bottom of the screen to display speed, altitude, GPS coordinates, distance to destination and so on.

I mainly use this app to explore a country (e.g. by car) on vacation, but it's also fun to use it on board to see what's that location below us.

You may switch off speed camera warning. I once got a warning over Switzerland. The 840km/h were well above the max speed limit of 120km/h, and the fine should have been in the order of seizing all property of the airline. For some reason, the pilot didn't care...

OK, lots of advantages, but there's also a drawback: The app can not just record your flight, though a menu for tracking exists. Nor can it display your currently covered track. It can only record a track when it's navigating you, but you don't want to hear "turn around! turn around!" all the time...

## Tracking app

Again, there should be thousands of apps out there. I'm using Open GPS Tracker, which can also display your position / track on an online map. So, you just see a point moving on a gray screen while flying.

However, this app allows to record your track, with up to one point per second, and at the end, you can export it as GPX file, which is the standard. It can be opened by many map tools, also by googles MyMaps or what it's called. The file contains coordinates, precision, time, altitude, speed, number of satellites and course.

One hint: This app makes a sanity check between speed reported by the GPS module and speed calculated from recorded points. If this fails, it doesn't display/record any speed. This often happens onboard, so switch this check off.

Here is a flight from Düsseldorf (DUS) to Las Palmas, Gran Canaria (LPA), including altitude profile, drawn with Marble (Linux KDE program):

## Precision

An airliner is usually made of aluminum, which makes it a huge faraday's cage. The reception of any radio waves is very limited (through the windows), and so is GPS. And as GPS needs a line of sight to several satellites spread as much as possible over the entire sky, the only chance is to have a window seat. There, I usually get a very good GPS signal, while it's already very bad to unusable on the next seat, and don't even think about it on the aisle seat.

Having a window seat, I usually get a good signal. While taxiing, the precision is quite good, as on this flight from Frankfurt (FRA):

Of course, the strength and accuracy of the GPS signal relies on the quality of the GPS module of your phone. My last phone wasn't so good, I often had jumps of several 100m sidewards, or from 7000m to 10000m altitude. This is just because accuracy comes with the number of satellites, which usually increases with altitude. And: The first aim of GPS is to locate your position, the altitude usually is less important. With my current phone, I don't see such problems. No sudden steps aside, and altitude and speed were quite the same as displayed on the entertainment system.

Well, not entirely. I noticed my phone showing an altitude about 50m too high when landing on my last flight. The 20m shown by the entertainment system were plausible, as the airport was nearly on sea level / in the sea. But the too high altitude was still there, even at the beach. Keep in mind the earth isn't a sphere, it's an ellipsoid, though even that's not correct, it's more like a potato. So, sea level isn't the same everywhere. High quality/price GPS receivers know this and contain data to compensate it, but cheap ones just use the ellipsoid model. (However, 50m is nothing during flight, and what do you expect from a phone inside the cabin...)

## More hints

For a working GPS, the receiver needs a list of all GPS satellites and their precise orbits ("almanach"), current time and its rough position. If it does not have its rough position, it takes much more time to get a fix (first GPS position). And if it doesn't have a recent almanach, it has to listen to the satellites for a while, as they slowly broadcast it.
As reception of radio signals is quite difficult inside the cabin, it may be very hard to get a fix, and even impossible to get the almanach.
So, it's good practice to prepare your phone before the flight, as reception will be better, and assisted-GPS allows to retrieve the almanach and current position via the mobile network.

Finally: The battery.
Running my two apps on a 4.5h flight takes about 80% battery, and I have a laaarge battery. Of course, this also depends on display-on time. But the endurance could by tested before the flight, and if it's too short, a power bank my help.

• My experience is that the display takes more power than the GPS, so it really depends on how much you are looking at the data rather than just recording. And of course don't forget to put the phone in airplane mode, the radio module is the biggest power hog. – Jan Hudec Oct 6 '15 at 7:17
• Does GPS really distinguish between altitude und position? I always thought GPS just gives you a timed 3D position and the rest is done by your local software by mapping the GPS position onto a model earth, where "altitude" is just a fancy word of saying "z component in relation to EGM96". – hiergiltdiestfu Nov 17 '15 at 10:43
• @hiergiltdiestfu: I'm not sure I understood you correctly. GPS determines the distance to the center of the earth, and using the known local sea level, it calculates the altitude (above sea level). The question is what data / model is used to define local sea level. Is it just an ellipsoid (like WGS84) or a more sophisticated one like EGM96? This may also just depend on the GPS device itself. – sweber Nov 17 '15 at 11:10
• Thank you for your reply, sorry for not being clear. I was referring to this part of your answer: "The first aim of GPS is to locate your position, the altitude usually is less important." I'm just trying to point out // ask whether it's actually valid to distinguish between altitude and position, when "altitude" is actually only a component of the 3D fix GPS does and only becomes "altitude" when translated onto some model of the earth. Or is it? – hiergiltdiestfu Nov 17 '15 at 11:16
• @hiergiltdiestfu: You can increase accuracy of one parameter if you allow a lower accuracy of another. If you use satellites just above the horizon, you can determine your (2D) position very precisely, but not the altitude. If you also use satellites above you, you'll also get a precise altitude. So, if a GPS device can handle just a few satellites, it would mainly use those above horizon, because people are more interested in position than altitude. – sweber Nov 17 '15 at 12:49

There's a great app for that info called GPS Status & Toolbox It gives you speed, altitude, longitude and latitude from your GPS. It will also give you pitch, roll, heading and acceleration data. None of this needs a data connection, just a view of GPS satellites. Never tried to get GPS from inside a plane, though. Not sure how well that works.

If you want to see your location on a map, if the plane doesn't have wifi, you'll have to download an offline map app. There's several of them available. The Google maps offline feature wouldn't work, really, because it only lets you download a certain size of tile. It took four such tiles to include the entire metro area of my home city (KC). It's pretty data heavy. Rural areas with less data can get a somewhat bigger tile, but if you're flying very far it would take forever, a lot of effort and memory space to download enough tiles to cover the whole trip offline.

• Thanks for the GPS Stauts & Toolbox reminder. Had it ages ago on my first 'droid, and it's quite handy, especially for calibrating the phone's sensors. I'd forgotten all about it! – FreeMan Oct 6 '15 at 14:35

This occurs pretty frequently in the GA community as apps like ForeFlight are quickly becoming the preferred method of navigation in small and even larger planes. There are a few problems that need to be overcome and ill outline them here.

Offline: Since you wont have access to the internet in the air you will need to cache the maps offline. There are lots of apps out there that do this in a variety of ways for a variety of reasons. Some are for hiking, others driving, and many for flying specifically. ForeFlight, FltPlanGo, and Garmin Pilot are just some of the ones that allow offline flight maps to be stored. Some of these apps require expensive subscriptions but they ensure that your data is always legal and up to date. If you are not a pilot FltPlanGo (free) is a cool one to check out. Flight based apps will also allow you to see cool info related to your flight like weather, approach plates and overlay over airspace maps instead of traditional road maps. ForeFlight even knows when you land and will pull up the airport diagram for you!

GPS: One of the major problems you will have is the GPS chip thats internal to the device. On one hand you have the fact that the airplane is a giant faraday cage as mentioned in other answers. This prevents you from getting a decent signal but even if you can get a good signal you will be plagued by the not so great GPS chip in most phones. This Article goes over it nicely

When using the iPad with only the internal GPS in your lap in the cockpit, we’ve found that the GPS tended to lose signal reception intermittently. Sometimes the iPad will not lock onto GPS again until you reboot your iPad.

but in general I have found the iPhone and iPad GPS to be less than optimal when I'm flying even small GA planes at far slower speeds. One of the best solutions to this is to get an external GPS receiver like this one they are small and provide great reception at all altitudes. Granted its a bit pricy just to know where you are on a commercial flight but it will do what you need it to.

(source)

INS: Your other option (and most airliners actually use this to navigate in some capacity) is to rig up a simple inertial navigation system with your phone. The issue this will induce is that you wont really be able to use your phone unless you don't move it. Using this method you can use the internal accelerometers to measure acceleration and calculate velocity in all 3 dimensions and inevitably deduce position from all that. There is at least one android app I can find that does it or you can (if you so chose) write your own. Along with not being able to move your phone INS systems also suffer from compounding errors which make them increasingly inaccurate as time goes on.

Dead Reckoning: This is one of ways pilots are taught to navigate and to some extent you could do it from your seat with a stopwatch, compass and map. If you know what plane you are on and you know its approximate speed (based on published numbers) you could compute your path. Practically speaking you will also need to know the winds aloft since your compass will read out the way the nose of the plane is pointing not the way its moving over the ground. Aloft you can easily have winds in excess of 50Kts or even 100Kts, if thats a direct crosswind your heading and ground track will be substantially different. As long as you know what the winds aloft are (For the US they can be found here) you can fill in the blanks.