External GPS - Do I really need it?

[newbiepilot]

Guys,

Quick question:

I have an iPad Mini (Wifi + 4G) and so it has a built-in GPS. From what I have read online, some people say you need an external GPS like Garmin Glo or DUAL XGPS160 for a reliable connection for your foreflight or Garmin Pilot App.

Anyone used foreflight or Garmin Pilot App without the external GPS reliably?

Any recommendation would be greatly appreciated.

 

[gprellwitz]

Some would argue that by definition a portable solution isn't reliable, hence the FAA's refusal to certify them. You aren't going to be using it as your primary source of location information (that would be your eyeballs and, if IFR, your instruments. So yes, based on my experience with FF and an iPad2, it's reliable "enough". You might get extra precision or coverage in some circumstances with an external unit. Remember, that's another battery to keep charged! If you go external, consider one that offers ADS-B In and AHRS.

 

[MickYoumans]

No, you don't really need an external GPS. I have an iLevil that has GPS, AHRS and ADS-B. If it were not for the ADS-B and AHRS I would not bother with an external GPS only device.

 

[Stingray Don]

The internal GPS seems to work well for me. Not worth the hassle unless you want ADS-b.

 

[PilotRPI]

I have an iPad Air that I use with iFly. I've never lost the GPS signal flying in a C172 and C150. I even get a weak GPS signal in my house. No plan on getting a dedicated receiver.

 

[James331]

No you don't.

I've had my mini cellular retena up to FL250 and in excess of 300kts in a pressurised AC, no issues.

 

[newbiepilot]

Great! Thats perfect. I just saved $100 bucks.

Thank you guys.

 

[DrPappy]

I use Foreflight on an iPad 2 with a Stratus. The other day my Stratus was not receiving. (OK, so I put it on the window below the wing in a 172, so it was my stupidity, not the Stratus.) I had to actually use a VOR to find my way. Anyway, I didn't remember that my iPhone 6 was in my pocket and could have functioned in a pinch just fine on it's own. The screenshot above is from my iPhone on a recent United flight from Florida to Texas.

 

[FORANE]

Does anyone know the Hz rate of the Ipads internal GPS receiver? How about the Hz rate of a 430W?

The internal GPS on my Asus TF700 is 1 Hz I believe. I found on approach that my position on the TF700 approach plate was different than the 430W. By using an external 10 Hz GPS receiver those positions correlated much better.

 

[MAKG1]

Don't compare an iPad GPS to a 430W if you want to maintain the myth that it's more than a toy…

Last time I did this, Foreflight happily reported 10m accuracy, but the 430W indicated it was off by about 0.3 miles at 1000 AGL, worse at higher altitudes. I've seen unreported errors as high as 5 miles.

 

[poadeleted20]

You do not need the external GPS -- the only time I've ever had a problem using my iPad mini Retina with internal GPS and Foreflight is in the middle seats in a wide-body airliner. Save your money, and save carrying around another box.

 

[James331]

Does anyone know the Hz rate of the Ipads internal GPS receiver? How about the Hz rate of a 430W?

The internal GPS on my Asus TF700 is 1 Hz I believe. I found on approach that my position on the TF700 approach plate was different than the 430W. By using an external 10 Hz GPS receiver those positions correlated much better.

I've flown my mini retena gsm with 530s and 430s, it's close enough to be fine, but remember it's not primary navigation, for the most part the location, speeds and whatnot have nearly always matched up with what my EHSI was saying.

 

[Ravioli]

I think you really do need an external. like the Dual. And I'll sell you one for $65 including shipping

I don't rely on the iPad2 internal gps. I now have a GDL39 which connects via wire to my 496 and via Bluetooth to my iPad.

So if anyone feels the need for a Dual... you know who to ask.

 

[woodchucker]

View attachment 40037

I use Foreflight on an iPad 2 with a Stratus. The other day my Stratus was not receiving. (OK, so I put it on the window below the wing in a 172, so it was my stupidity, not the Stratus.) I had to actually use a VOR to find my way. Anyway, I didn't remember that my iPhone 6 was in my pocket and could have functioned in a pinch just fine on it's own. The screenshot above is from my iPhone on a recent United flight from Florida to Texas.

That's quite a few decimal places there! Kinda making me twitch a bit.

 

[woodchucker]

Don't compare an iPad GPS to a 430W if you want to maintain the myth that it's more than a toy…

Last time I did this, Foreflight happily reported 10m accuracy, but the 430W indicated it was off by about 0.3 miles at 1000 AGL, worse at higher altitudes. I've seen unreported errors as high as 5 miles.

Which is why I use a Bad Elf paired with Foreflight. Well, that and the iPad my school gave me lacks the cellular option anyways.

If you are screwing around with complicated airspace, I might suggest the external GPS. If you are just banging around the countryside VFR, then maybe it's not a big deal.

 

[poadeleted20]

If you are screwing around with complicated airspace, I might suggest the external GPS.

If you're doing that, get a certified unit. And even then, don't press the edges of the airspace too close lest you be detected by ground-based radar as having crossing the line (as has happened to countless pilots around the DC area trying to skirt the SFRA by about a wingspan).

 

[gitmo234]

If you're doing that, get a certified unit. And even then, don't press the edges of the airspace too close lest you be detected by ground-based radar as having crossing the line (as has happened to countless pilots around the DC area trying to skirt the SFRA by about a wingspan).

Thats incredible. I was planning to pick up a passenger very near the SFRA the other day and wasn't comfortable with it. Note: I'm not afraid to file the flight plan to enter the SFRA, I just dont like coming close to it AT ALL. There's a lot of room to fudge on a lot of things but the SFRA is one, and not one I'd choose to push the limit on.

OP - Way back I got a steal on an iPad mini without cellular. That GPS will not serve the purpose (its wifi based). I hear an iPad with a cellular chip will do just fine. I have used the Dual GPS with Garmin Pilot and it worked great, and tomorrow I'm flying cross country for a meeting using foreflight and Stratus and will report back.

I converted from Garmin Pilot because foreflight has more features I like, and the interface is going on me. I opted for Stratus because I fly a lot for a private pilot so I want something that gives some weather depiction.

I use my Garmin 430 on board for primary, iPad and foreflight as secondary navigation (and I look up information in flight on it), and my Garmin D2 watch as my contingency plan.

EDIT: One thing I dont like though, is the need to charge (potentially in-flight) all these different things. I try to keep my cockpit from looking like my car on a long cross country drive with 800 things charging of the 12v port. Tomorrow I'm flying 2 hours for a meeting, and then 2 hours home, may need to charge on the way back.

Later this month I'm making a 7 hour one-way cross country for a few days for a vacation.... really going to have to charge

 

[poadeleted20]

Thats incredible. I was planning to pick up a passenger very near the SFRA the other day and wasn't comfortable with it. Note: I'm not afraid to file the flight plan to enter the SFRA, I just dont like coming close to it AT ALL. There's a lot of room to fudge on a lot of things but the SFRA is one, and not one I'd choose to push the limit on.

Just goes to show that you're smarter than a few hundred other pilots around here who violated the SFRA while trying to fly around its edges and failed to stay outside it.

 

[gms5002]

EDIT: One thing I dont like though, is the need to charge (potentially in-flight) all these different things. I try to keep my cockpit from looking like my car on a long cross country drive with 800 things charging of the 12v port. Tomorrow I'm flying 2 hours for a meeting, and then 2 hours home, may need to charge on the way back.

Something like this might help reduce the clutter depending on your cockpit layout. http://www.amazon.com/Poweradd-Pilo...LPZ4/ref=sr_1_1?ie=UTF8&qid=1434638749&sr=8-1

 

[MAKG1]

Which is why I use a Bad Elf paired with Foreflight. Well, that and the iPad my school gave me lacks the cellular option anyways.

If you are screwing around with complicated airspace, I might suggest the external GPS. If you are just banging around the countryside VFR, then maybe it's not a big deal.

What measurement did you do to establish that the Bad Elf accuracy is any better than the internal?

Just because it's "different" doesn't mean it's better. It might be, but you can't know without measuring it.

I own an external GPS, but I don't use it in general because bluetooth drains batteries and I consider it to be an extra toy. I do not trust the Angry Birds device to tell me where I am, as every detailed measurement I've made has fallen short of what it says it can do.

 

[woodchucker]

What measurement did you do to establish that the Bad Elf accuracy is any better than the internal?

Just because it's "different" doesn't mean it's better. It might be, but you can't know without measuring it.

I own an external GPS, but I don't use it in general because bluetooth drains batteries and I consider it to be an extra toy. I do not trust the Angry Birds device to tell me where I am, as every detailed measurement I've made has fallen short of what it says it can do.

How accurate are we needing it? I'm a VFR only pilot, with no installed GPS in the plane I use (not my plane). For 90-95% of my flight time, the iPad is off, and I fly visually referencing paper charts. When I do have the iPad on, and check the plane's GPS position with what is below me, it "seems" to match quite well. No, I don't have a measurement, and I don't think I need one. It's not a toy, and I don't put full faith in it, but it is there as a backup.

 

[MAKG1]

How accurate are we needing it? I'm a VFR only pilot, with no installed GPS in the plane I use (not my plane). For 90-95% of my flight time, the iPad is off, and I fly visually referencing paper charts. When I do have the iPad on, and check the plane's GPS position with what is below me, it "seems" to match quite well. No, I don't have a measurement, and I don't think I need one. It's not a toy, and I don't put full faith in it, but it is there as a backup.

You claimed you used a Bad Elf because it was better.

Why do you think it is better?

For what purpose do you use this GPS? I find it's not useful for anything in VFR weather, aside from displaying charts. I've tried to use the internal GPS for search patterns and aerial photography patterns, and it's not good enough. Everything it tells you about position has to be verified by other methods that might as well be primary. That makes it a toy.

An external GPS is another object to be powered by your battery. That has a cost.

 

[gitmo234]

Probably one of the better ways to test it is to use an app that shows the accuracy at any given time. I'd be willing to bet an external dedicated GPS is more accurate but if you're worried about 5 - 10 meters one way or another you probably shouldnt be using something portable

 

[LDJones]

Some would argue that by definition a portable solution isn't reliable, hence the FAA's refusal to certify them. You aren't going to be using it as your primary source of location information (that would be your eyeballs and, if IFR, your instruments. So yes, based on my experience with FF and an iPad2, it's reliable "enough". You might get extra precision or coverage in some circumstances with an external unit. Remember, that's another battery to keep charged! If you go external, consider one that offers ADS-B In and AHRS.

The internal has proved to be one of the best GPS units I've ever used. It locks on places where my portable Garmins have not. I've flown many, many hours with it alongside a Garmin 430W and never seen the slightest hint of discrepancy or loss of signal.

I see no reason to have an external, except for one built into an ADS-B receiver!

 

[LDJones]

You do not need the external GPS -- the only time I've ever had a problem using my iPad mini Retina with internal GPS and Foreflight is in the middle seats in a wide-body airliner. Save your money, and save carrying around another box.

Not to mention managing one more battery.

 

[MAKG1]

Probably one of the better ways to test it is to use an app that shows the accuracy at any given time. I'd be willing to bet an external dedicated GPS is more accurate but if you're worried about 5 - 10 meters one way or another you probably shouldnt be using something portable

If you don't know how the app calculates that accuracy, it's meaningless and you can't draw any conclusions.

I've demonstrated that Foreflight's "accuracy" is missing something. It must when it claims 10m accuracy, but it differs from standards by 100 times that or more.

I suspect it's just counting satellites or something excessively rudimentary like that.

It's very common for people who don't understand measurement error to underestimate it substantially. Particularly when errors are correlated.

 

[Alfred Austria]

I like my iPad w/foreflight and internal GPS. It gives me a "rough enough" estimate on position to augment my situational awareness. I don't think anyone here would claim its going to replace a purpose built, GPS NAV system, but it has its own utility.

 

[woodchucker]

You claimed you used a Bad Elf because it was better.

Why do you think it is better?

For what purpose do you use this GPS? I find it's not useful for anything in VFR weather, aside from displaying charts. I've tried to use the internal GPS for search patterns and aerial photography patterns, and it's not good enough. Everything it tells you about position has to be verified by other methods that might as well be primary. That makes it a toy.

An external GPS is another object to be powered by your battery. That has a cost.

Better than relying on a cellular signal on the iPhone. Okay, fine, it's a toy. Your car is also, it certainly isn't giving you 4 decimal accuracy on speed and miles driven.

You may need DoD accuracy for aerial photography, but the vast majority of us who fly VFR on a PPL, we don't need your certified and installed unit. The toy works fine, providing situational awareness, flight planning tools, and rough location (plus or minus 500 miles). This is truly a mundane argument. Not all of us own our own planes. I can't just drop $50K or whatever the cost and install a certified unit in the plane. I fly with what I have. The OP was wondering if he can get by without an external GPS. My original answer was maybe, depending on what type of flying they are doing. In the west, you won't get a cell signal to fix your location in a lot of places. At altitude it's less reliable. An external GPS will give a better and more accurate signal.

ps: the Bad Elf has a battery that lasts something like 10 hours. Yeah, I bring a cable to charge it on overnight trips. BFD.

pps: I normally enjoy your posts. You have much more flying experience than me. However, you are being a bit pedantic on this topic.

 

[SbestCFII]

Without the external source, there will always be some configuration, position or heading where the GPS data will drop out from time to time. If you want ADS-B In data, the DualXGPS160 works with some apps, like WingX, Stratus for ForeFlight, and GDL-39 for Garmin Pilot. If you just want GPS data, the Dual XGPS150 is fine (and cheap) for just about any device. If you're not flying IFR / MVFR with weather about, then that's all you really need.

 

[gitmo234]

If you don't know how the app calculates that accuracy, it's meaningless and you can't draw any conclusions.

I've demonstrated that Foreflight's "accuracy" is missing something. It must when it claims 10m accuracy, but it differs from standards by 100 times that or more.

I suspect it's just counting satellites or something excessively rudimentary like that.

It's very common for people who don't understand measurement error to underestimate it substantially. Particularly when errors are correlated.

More than likely it would know by the size of the triangulation window. Given the number of satellites reporting your position, it triangulates down to an area. If that area is 1 meter wide/long, etc then the error rate is 1 meter. Its one of the only ways it really makes sense to calculate and I'd bet thats how its done.

Some GPS systems that arent dedicated GPS units for Position, Navigation and timing (PNT) only use the minimum of 4 which could potentially leave broad areas, as much as 30 meters. FitBit is a good example. They had some serious issues with their high end model that only those of space satellite operations guys understood. I went on a 4 hour run in colorado and according to it I ran .3 miles. A PNT dedicated device, that isnt designed to be "pretty good at posting your general location on facebook" is far more likely to be more accurate.

 

[Stewartb]

My 4G iPad and iPhone GPS performance has been flawless. Add a Garmin GLO? No difference. Add a GDL39 3D? No difference. The GDL offers some new features but the GPS location is no better than the device was on it's own. I still run an Aera in the panel as a backup but have never needed it or seen any disagreement between GPS devices. There's a broad NOTAM in Alaska right now that the Gov't is testing GPS degradation and that GPS signal may be compromised or completely unavailable. With the smokey conditions and reduced visibility that has most of us paying closer attention. And this isn't the first time the DOD has tinkered with GPS up here. So far my original comments are validated. Probably more impressive is how easily the iPad and iPhone acquire position during a 500mph commercial flight at 36,000' while sitting inside an aluminum tube. Life in Cessna seems pretty low demand by comparison.

 

[MAKG1]

This is truly a mundane argument. Not all of us own our own planes. I can't just drop $50K or whatever the cost and install a certified unit in the plane. I fly with what I have. The OP was wondering if he can get by without an external GPS. My original answer was maybe, depending on what type of flying they are doing.

Actually, you can do better by eye, correlated to a topo map or even a TAC (a sectional doesn't quite have enough detail, but it's close). You just have to look for the fine details. Those TACs are surprisingly accurate; I've done searches over the Sacramento Delta using the SFO TAC, and every bend in every waterway is RIGHT there.

The gripe I have is that the toy claims 10m or 30m accuracy when it is clearly a lot worse than that. You may think it's pedantic, but it means you cannot believe what it is telling you, and you have no way to gauge how reliable it is.

And yeah, the one in my car is a whole lot worse. I've seen 10+ mile errors in that one. It's rather obviously not detecting that it's looking at reflections off terrain.

Panel mounts have errors, too. One of our mission pilots yesterday showed me the G1000's maximum recorded ground speed -- and it was over 750 knots. In a 182. You have to be skeptical about what the technology is telling you. It does occasionally lie.

And the way you do that is by using independent methods to verify. No, one GPS against another isn't sufficient (it can show a lower bound of error, but a good comparison does not rule out that both of them are giving wrong answers -- they are not truly redundant).