Ipad - rubbish GPS?
 

This pic

http://www.zen74158.zen.co.uk/ipad-m...rap-gps-mm.jpg

taken from the Memory Map data screen shows the GS as 54kt, when the actual value was about 130kt.

One could argue that maybe the GPS was still working out a fix, which is indeed true, but look at the "GPS Accuracy" figure of "10.9 yards". How can those two be true concurrently? It's obviously a serious bug somewhere.

What the Ipad2 GPS does is, following startup of the app, it gradually winds up its GS figure to the correct value, over a few minutes.

My iPad seems to have good & bad days on a good day it will give the same results as 2 FMC's that are fed by 2 GPS and 5 DME units.

On a bad day it fails to get a fix.

i would more argue that memory map is rubbish.

I have no knowledge of Memory Map, but all the testing we have done with the iPhone GPS has led me to believe that it is all but useless for anything more sophisticated than finding the nearest McDonalds. I would expect the iPad to be similar.

The antenna is poor and the kalman filtering is very poor - this is what leads to the speed inaccuracy issues and the slow ramping up of speed when the device is first switched on.

I could go on.....

In Apple's defence it's actually quite astonishing what they have packed into such a small device.

I find the Ipad/Iphone GPS to be very good (much better than any GPS built into a "computing device" that I have ever had) for road nav (TomTom) but that seems to be because it is getting GSM assistance, or possibly because the speeds involved are much lower.

The problem with it reporting a high fix accuracy, at the same time as the app is reporting a patently ridiculous GS, means that there is no obvious way of knowing whether to trust it.

I have had cases of the fix doing odd things and then when I looked at the GS that was found to be too low. This happened after it was all OK earlier, which is very unusual for any GPS.

Interesting. My only use - so far - of the iPad was in an AA5, looking at practical uses of Airnav Pro during an IR course. Seriously impressed me, it would never be an absolute primary aid but as a backup it would be foolish to not use it if it was available. The CAA FE who came to test the candidate had a similar view...

This "primary" and "backup" stuff is meaningless, legally and practically. It comes down from some ex RAF navigator in the CAA :)

But the basic point is that a GPS needs to be trusted, whether you actually fly with it for real, or are pretending to be doing a Battle of Britain and just glimpse at it occassionally. If you cannot rely on it, it is a chocolate teapot.

I think the Ipad looks really pretty. In anything but strong light the display is very good. The good battery life makes it a good platform for this kind of stuff.

But my experience so far of the built-in GPS is that it has some weird faults and I cannot see how it can be trusted.

Sadly true a few years ago - although most of the problem was propagated by non-ex RAF CFIs with habits. Things are changing though! I think you know what I mean though based on your last paragraph. It can't be totally trusted.

Then again, I've experienced several recent in flight GPS failures of a new & very certified GNS430, which is a very nice primary nav device. Ah well. Oddly enough the iPad kept lock throughout those events ;)

Well, nothing can be totally trusted. Nothing.

The pilot's job (among others) is cross-checking information from multiple systems.

The GNS430 probably had a dodgy antenna or antenna connection, or you have the old VHF 11th/13th harmonic problem.

We think a slightly patchy connection - not helped by being at the top of a comm stack with imperfect ventilation, especially some Narco units which were putting a lot of heat out and still not achieving much. Fortunately the candidate's own aircraft...

It depends on the frequency of the gps updates. If they're regular enough then 1cm accuracy could conceivably show a speed in the opposite direction of travel for one update.

Would need more info to determine whether the data being presented was due to a bug or just acquisition period anomalies.

Ps. If the data is averaged over a few minutes then the starting accuracy of say 1km could out a position 1km ahead of your track, taking a massive chunk out of the average speed for a few minutes.

A lot of these devices only have AGPS (assisted GPS) which is based on cell phone towers, only good for ground based use. Best to use a bluetooth connected real GPS reciever.

The "Ipad/3G" has a real GPS.

Any positioning method based on GSM would do zilch when airborne.

Unfortunately I don't have another GPS moving map app to test against MM, and I don't think there are many that run the CAA 1:500k charts anyway. Oziexplorer is being developed for the Ipad and that will really open things up when it comes. That's assuming the GPS is usable in flight at all...

A/GPS is a real GPS, it uses the cell locations in order to improve the lock time before the full almanac is available. Away from cell towers it just takes longer to lock on. The older the almanac the longer it takes.

A bit of research before repeating old wives tails as fact perhaps?

Try AirNav Pro. That uses the same chart and seems to be much better than memory map for accuracy. Not to mention the fully functional Nav tools.

My iPad has no GPS so I bought the GNS5780. With Air Nav Pro this invariably seems to display the same speed as my Sky Demon system.

I can't totally recommend the GNS unit as it has a habit of turning itself on in my flight bag and flattening its battery. Also there is no battery life indication. Other than that it works well with the iPad.

I've just completed a 30hr cross country with nothing but the Ipad and Foreflight. Worked great and accuracy was always very good. Couple of times it lost satellites, but never for more than maybe 30 sec. Didn't overheat up high either. Good stuff. When I redo my panel (in year 2032 by the likes of it...) I will give it a dedicated dock right on the dash.

I am sorry to say this but that is absolutely rubbish behaviour.

If it just lost the fix for 30 secs, why not a couple of hours?

A GPS is absolutely not supposed to do that.

After reading a thread on this very website only a few weeks ago i rushed out and bought an Ipad, Bluetooth receiver, Memory map, All uk maps and guess what... Iv now sold it because it was SH*T!

As IO say's, If it looses signal at all then it just isn't good enough!

I sat for 10 min's with open clear sky before i got a signal on 1 occasion


(Still got my Airbox Clarity, And it's never failed me! And gives correct speed)

I think all that has been proved here is that the Memory Map app probably sucks.

Looking at that screenshot, it appears the app has been written by a seven year old. If their speed calculation algorithm is as good as their GUI design, then you have your answer.

You really need to try some different software before blaming the hardware.

Not going to get into this, never going to be problem for me, but I have had one experience of it recently, flying with a friend in his 172 from San Fernando Valley (Whiteman ) to Santa Ynez N.E. of Santa Barbara, California.

I felt uneasy at not being able to open a chart to see the route from end to end, moving sections of "the sectional" around the screen just wasn't the same, and zooming out made everything too small, tho' zooming in helped read all the airport information without having to find my glasses !

Following the blue line also meant I lost some situational awareness, I felt I was doing what I was told rather than working out what I had to do, which keeps one firmly in the loop.

It was nice to be able to get live Met. tho', especially as we flying early morning and fog clearance was a factor.

Not a fan of digital devices anyway, I don't "read" my instruments, or watch, so much as "look at the picture". I "know" the ASI needle is about 3 o'clock on the dial on final approach, and can see that out of the corner of my eye as I concentrate on flying the beast, I don't have to read and assimilate tumbling numbers and the speed at which the needle moves relates more to what I'm trying to achieve, as well, much more user friendly then just numbers moving at different speeds.

and I detest, with a vengeance, touch-screen technology, so the iPad will never be for me - best of luck flying an ILS in turbulence trying to look for information on your eyepad. Big dials and big knobs ( if you see what I mean ! ) for me.

But best of luck chaps, a Brave New World out there.

I don't need it, but interesting to read about your trials and tribulations.

You fail to add that for $399 you get moving map, complete database, weather, fuel prices and tons of other stuff, all with very good reliability. That's pretty spectacular. If you want to shoot WAAS approaches down to 1mm, then by all means fork out £15000 for the new Garmin GTN 750.

I agree with IO540 on this. A toothbrush is no more useful as an aviation nagivation device just because it's even cheaper than an iPad. A product is either useful for a purpose or not, and I think the point being made is that the iPad is not useful for the purpose of an aviation navigation device IF you want to be able to rely on it to a realistic level. Nothing is 100%, but it sounds to me as though many people are experiencing something like 70%, which is all but worthless in the cockpit.

I've tried the iPad in flight, and it's fun / worth having onboard, but to be honest I'd only use it as a document reader for plates, and a last ditch backup for a GPS in an emergency.

The problem is not so much the times when you look at it and know it's gone wrong, it's the fact that you may be looking a spurious, but realistic-looking information.

The original image, in the OP, however does not indicate on its own any kind of fault. Any GPS device needs time to acquire and settle down. The only negative I could say is that the software should probably indicate the predicted accuracy of the information being displayed, to avoid someone misreading it as meaningful info.

My Garmin 296 does it all the time....

Memory map is the problem - it's rubbish. I've used AirNav Pro and Foreflight extensively (over 100h flying) and never had any positioning problems. One reported issue is to do with what case you may or may not keep the iPad in - those with closing lids have been known to blank the signal.

Just to widen the discussion, two questions:

why would you want to buy something like an iPad to use as a GPS when there are so many dedicated GPS units out there; and (unconnected to the first)

What is the best GPS in terms of battery life? I ask this because I personally now fly aircraft without internal power so tha battery is all important. Most seem to run for no more than an hour and a half without additional utems like power monkey etc.

Justiciar,

Get a Garmin 96 or 96c (they don't make the b&w 96 any more, but they can be had on Ebay, etc; the 96c is still in production). Has a - proven - battery life of about 15 hours. Two caveats:
- there is no meaningful warning when the batteries go down, so always have spares handy (or change every 8 hours or so, there is a battery timer built in)
- the battery life decreases if you use an external antenna that's powered from the unit. Not by much, but worth keeping an eye on.

I didn't buy my Ipad to use it as a GPS. I started off by carrying it in the cockpit as a cross check to my new £1600 installed GPS, then found to my surprise that it was actually far easier to use and more reliable than the dedicated unit. Now I don't bother to switch the installed one on.

I also find that the varifocals which I wear when flying have the near focus (reading) portion exactly in the right position to read the Ipad screen when it is on my leg strap, so I don't have to keep slanting my head up and down like a chicken to read the panel mounted one clearly.

What installed GPS is less reliable than an iPad?

Thanks 172driver. You don't happen to have anything a bit more modern to recommend do you? Something aviation dedicated. The problem is that you always have to heavily discount any battery life, so something with at least a good 2 hours endurance in real conditions would be good.

If budget permits, I would highly recommend the 795. It isn't exactly the longest battery life, but it's an astonishingly good device, and has about a 2 hr battery life if you leave it on solid, and on full brightness, but this is increased dramatically if you turnt he brightness down a bit.

And now, I've taken to letting it blank the screen when you don't touch it for a while.. you just touch the screen and it blinks immediately into life. This seems to have dramatically improved battery life also.

The G96 and 96c are aviation dedicated and have very long battery life, a good fifteen hours or so. The units give penty of warning of when a battery change is necessary. The 96c is still in production I think, (and I have a 96 for sale!)

I enjoy much the AV8OR, the 800 mAh is about 2 hours and the 1600 mAh (optional) lasts 4 hours at least at full luminance. No external receiver, no wires in the cockpit. I take both with me. It is a nice GPS, especially the profile view while flying in the mountains of Thailand.
The iPad was born immediately after I bought the AV8OR, which did not make me happy. But now, reading this thread (and more) I think it turns out to be the right choice!

I think the Ipad suffers from the same (inevitable) problem which all "computing devices with a GPS" suffer from: interference from the CPU etc messes up the GPS badly, and its design needs to be significantly compromised to work at all.

Any GPS receiver design is a compromise between initial acquisition time, accuracy, ability to hold a lock once acquired, etc.

For example a satellite phone might acquire a fix in seconds (it would be inconvenient otherwise, since they all need a GPS fix to make a call, for some reason) but might be pretty inaccurate afterwards.

In the I-devices, Apple use GSM and perhaps WIFI location services to give the GPS an initial fix, and to support the GPS afterwards. This is why that GPS is so good on the ground. But once you lose the assistance, you are back to a basic GPS design which is probably not very good anyway, and suffers from internal interference.

I would like to see an external GPS for the Ipad which has an external power input and an external antenna input. A GPS whose internal battery needs to be charged is just more hassle.

I don't know if this works with iDevices, but with Android you can override the built-in GPS with an external GPS receiver connected via bluetooth. I've had good results with an ageing Holux GPSlim:

Holux GPSlim (GR-236) Review

which has connections for both external power and an external antenna.

While certainly not the most modern of kit, it does what it says on the tin (and actually is aviation dedicated; you can load other non-aviation databases, though). Coupled with an external antenna it works a treat, also in some VERY remote parts of the world! Of course there are better units out there, but the problem, as I see it, is that many more modern devices simply devour the power :{

Sillert - AIUI, Apple have made the Ipad incompatible with every "normal" bluetooth GPS. So the SIRF-3 models your link shows won't work. I have tried a few of these myself; the Ipad doesn't even see the bluetooth device :ugh:

There are just a few GPSs which are IOS compatible.

The problem for me is that I would want a neat and tidy installation. Even though I fly only my own plane, which nobody else flies, I still don't want power cords etc all over the place. So my old Emtac bluetooth GPS is velcroed away under the dash, is connected to a power feed (from the aircraft, via an approved power connector which was installed even before the plane had its original UK CofA inspection ;) ) and is connected to a rooftop aviation-style GPS antenna which comes out on a BNC connector. The GPS itself has an internal battery which is good for 5-10 hours, but that is just a bonus.

Thanks again. I didn't spend enough time researching the model before replying. I see you can get a wrist strap. Again useful; I have flown in the Chipmunk with a Flymap (the old one based on the road angel) strapped to my knee but this means bending the head right down and squinting at the small screen from a little too far away - not good for keeping a lookout. Definitely one to explore further.

One more thing, Justiciar. The 'external antenna' bit is relevant in a Cessna, as the high wing obstructs satellite reception if the unit is yoke-mounted. In a Chipmunk flown in the UK (i.e. with plenty of satellites available), operating w/o the antenna should not be an issue.

My G96 works just fine on the yoke of my C206 without any external antenna.