Nexus 7 loss of GPS

LDJones

LDJones

Touchdown! Greaser!
Gone West
Joined
Sep 6, 2011
Messages
10,998
Location
Twin Cities, MN
Display Name
Display name:
Jonesy
Today I had to fly out to the oil patch in western North Dakota in the Duke. I had my iPad 4 with 4G on my lap and my Nexus 7 in a RAM mount on the side window. My buddy had his iPad Mini on his lap. We had solid reception on the iPads but I could not get a GPS signal on the Nexus. None. GPS Test would struggle to even see a couple of satellites and would never even go yellow, much less green on a signal. Then it would time out. This was true even laying it up on the dash. Even rebooted it.

I decided it must be a Duke anomaly (although I am pretty sure I've used it a few times before in the Duke.)

Got back from ND early afternoon to fly with some students and found it would not get a signal ANYWHERE! Checked all settings. Nothing.

Now, lying in bed trying to figure out what's going in, it is suddenly working, but seems clueless about previous glitches! Anyone else see this after 4.2.2 update?
 
Last edited:
On the other thread I reported that I was seeing the altitude off quite a bit. I loaded the GPS test app and have been looking at the signal when the altitude is off. Sure enough, the signals are dropping. The iPad held steady with the XGPS150 antennae. Anyone visit a forum for these units and see if there are complaints about the GPS function?


Sent from my iPad using Tapatalk
 
Marauder said:
On the other thread I reported that I was seeing the altitude off quite a bit. I loaded the GPS test app and have been looking at the signal when the altitude is off. Sure enough, the signals are dropping. The iPad held steady with the XGPS150 antennae. Anyone visit a forum for these units and see if there are complaints about the GPS function?
Click to expand...

A google search turned up a few gripes here and there related to 4.2.1 but nothing directly related.
 
LDJones said:
A google search turned up a few gripes here and there related to 4.2.1 but nothing directly related.
Click to expand...

I'm beginning to wonder if I don't have a hardware issue with the GPS receiver in this unit. Although the altitude information in the Garmin Pilot is advisory only, sure would be nice if I could trust it.


Sent from my iPad using Tapatalk
 
Marauder said:
I'm beginning to wonder if I don't have a hardware issue with the GPS receiver in this unit. Although the altitude information in the Garmin Pilot is advisory only, sure would be nice if I could trust it.


Sent from my iPad using Tapatalk
Click to expand...

Up a few post you mentioned that you were using a supplemental GPS receiver with the iPad. Can you hook up the Nexus 7 to it? That would be a good way to test your theory.
 
Jay Honeck said:
Up a few post you mentioned that you were using a supplemental GPS receiver with the iPad. Can you hook up the Nexus 7 to it? That would be a good way to test your theory.
Click to expand...

I certainly can Jay. I actually was thinking about doing this on my deck first just to see how much different they were in a controlled environment. All I know at this point the altimeter, iPad and Garmin panel mount GPS all agree. The Nexus won't -- some of the time. I will keep you posted on the experiment.


Sent from my iPad using Tapatalk
 
I've had this issue while flying, as well -- I don't know if it's OS related (I run a custom ROM), or hardware related, but I eventually ended up buying a Dual XGPS150, which works great.
 
roddie said:
I've had this issue while flying, as well -- I don't know if it's OS related (I run a custom ROM), or hardware related, but I eventually ended up buying a Dual XGPS150, which works great.
Click to expand...

I've never lost lock with the Nexus 7's built in GPS in any app. Of course, I now use the GDL-39's GPS in flight.
 
I am shocked, shocked, some Nexus 7 may have a flaw! :D

Just to report, the two I got as replacements for the two that bricked after a couple of weeks are running fine now. I suppose the QC slips during the pre-Christmas production has been fixed.

Cheers
 
X3 Skier said:
I am shocked, shocked, some Nexus 7 may have a flaw! :D

Just to report, the two I got as replacements for the two that bricked after a couple of weeks are running fine now. I suppose the QC slips during the pre-Christmas production has been fixed.

Cheers
Click to expand...

Good to hear.

Re: Flaws. Any mass produced device is going to be subject to potential flaws. Your experience proves it, and was like lightning hitting the same spot twice -- which DOES happen.

Meanwhile, my "ancient" N7 (purchased right after they were introduced last summer) keeps chugging away. It is used daily, for everything from a countdown timer (at the grill) to a WiFi signal analyzer at our hotel. It's as bulletproof as any computing device I've ever owned. Battery life is still great, and the screen is still perfect, despite taking one really nasty fall out of Mary's purse.

Although I can see its days are already numbered. An upgraded Nexus 7 is rumored to be in the works, with removable storage, more RAM, and two cameras. But that's the beauty of the Nexus line -- they're so cheap, relatively, that you're not angry when an upgrade comes along.
 
My daughter managed to damage the usb connector - it wouldn't charge, so it's off to texas for repair.

Sure wish those damn pogo-pin docks were easier to find. They're going on eBay for $200!!!
 
TMetzinger said:
My daughter managed to damage the usb connector - it wouldn't charge, so it's off to texas for repair.

Sure wish those damn pogo-pin docks were easier to find. They're going on eBay for $200!!!
Click to expand...

Really? Dang, glad I got one when I did!
 
Marauder said:
I certainly can Jay. I actually was thinking about doing this on my deck first just to see how much different they were in a controlled environment. All I know at this point the altimeter, iPad and Garmin panel mount GPS all agree. The Nexus won't -- some of the time. I will keep you posted on the experiment.


Sent from my iPad using Tapatalk
Click to expand...

roddie said:
I've had this issue while flying, as well -- I don't know if it's OS related (I run a custom ROM), or hardware related, but I eventually ended up buying a Dual XGPS150, which works great.
Click to expand...

Reporting back for duty! Well, I did the side by side taste test and our customers preferred, 2:1, the XGPS150 over the Nexus 7 internal GPS.

There is definitely a big difference between the altitude report outs between the XGPS150 and the internal Nexus GPS. The Nexus using the internal GPS will routinely report 300 to 400 feet difference (always with the Nexus reporting lower) than actual altitude. The XGPS150 will always be within a 100 feet of the Aspen, altimeter and Garmin GPS.

Hmmm... do you think I can go back to Staples and ask for a replacement based on a bad GPS signal?
 
Marauder said:
Hmmm... do you think I can go back to Staples and ask for a replacement based on a bad GPS signal?
Click to expand...

Why not? They took back the two that bricked on me with no problem.

Can't hurt to ask.

Cheers
 
X3 Skier said:
Why not? They took back the two that bricked on me with no problem.

Can't hurt to ask.

Cheers
Click to expand...

I think I will try. A brick is easier to sell as a problem than a 300 foot altitude error ;)
 
Marauder said:
I think I will try. A brick is easier to sell as a problem than a 300 foot altitude error ;)
Click to expand...

I don't get it. An altitude reported from an uncorrected (by barometer) GPS should be "off" by the same amount, no matter the unit it's displaying on.
 
I don't get it either Jay. Phase II of my testing will be to run the Garmin ap on the iPad and see what I get for altitude and switch it immediately over to the Nexus and see what it gives me. Both using the XGPS150.

They should both have similar altitudes, right? And the difference between those altitudes and what I see on the altimeter should differ by how much? Maybe I am expecting too much :)
 
Marauder said:
I don't get it either Jay. Phase II of my testing will be to run the Garmin ap on the iPad and see what I get for altitude and switch it immediately over to the Nexus and see what it gives me. Both using the XGPS150.

They should both have similar altitudes, right? And the difference between those altitudes and what I see on the altimeter should differ by how much? Maybe I am expecting too much :)
Click to expand...

Well, in fairness every aviation GPS clearly states that altitude readings are inaccurate. The earth simply isn't a perfect sphere, so there is no way to make a geometric model that will give you anything but an approximate height without barometric information.

That said, I would expect both GPS altitudes to be off by the same amount.
 
Jay Honeck said:
That said, I would expect both GPS altitudes to be off by the same amount.
Click to expand...

Is that a realistic expectation between a tablet GPS and a dedicated GPS that is sold for aviation (and other things)?

Do they both "sample" at the same rate? I don't know anything about the inner-workings of a GPS, but I would expect the DUAL to be more "accurate" in a way.
 
AFIK, all or nearly all GPSs' output data is in NMEA format. (National Marine Electronics Association -- apparently they got to GPS before we did.).

The NMEA data stream consists of "sentences" of various types: http:\\aprs.gids.nl/nmea/

Among the things in the $GPGGA sentence is Altitude. This is a calculation relative to a flattened sphere/approximation to the earth's shape, so the result is an approximation. More here: http://www.avionicswest.com/Articles/GPS Altitude.htm

I haven't paid serious attention to portable GPSs for a couple of years, but at that time the most common GPS chip set was the SIRF STAR III, which produces the NMEA serial data stream. This chip set was and maybe still is used in the majority of the little bluetooth GPS receivers like the GlobalSat. The Dual GPS uses a chip set from Skytraq, which also produces the NMEA data stream.

So takeway #1 is that computers getting data from the same GPS chip set should be indicating the same altitude.

#2 is that if the N7 is indicating an erroneous altitude, it is likely a fault with its internal GPS. With an external GPS, the error should go away or at least be different. I am too lazy to fool with this myself but I will be interested to read here how the experiment goes. :)

HTH
 
Well, my Nexus GPS went south on me again today. GPS Test would show half a dozen satellites in view but most would be grey. Flew for two hours and only had satellite lock for a few minutes. Very frustrating. Debating if I should send it in (I assume it has a year warranty, no?). Glad I wasn't relying on it for a x-c.
 
Do you have a case on it? Worth trying without the case maybe?
 
What kind of airplane and where was the N7 held or mounted?

I flew right seat in a 182 a week or so ago and had trouble when my N7 was suction-cup mounted at the front of the side (door) window, a bit under the wing. When I moved the suction cup just forward of the door pillar onto the windshield the N7 got a better view of the sky and the GPS recovered. We were northbound so fewer satellites were probably in view.

I used the side window for mounting the N7 in a 195, which would seem to have the same wing-blocking-sky characteristic and had no problems. In this case we were flying approaches so the sky view varied quite a bit.
 
Last edited:
Challenged said:
Do you have a case on it? Worth trying without the case maybe?
Click to expand...

Nope...no case. Crazy thing is when I first got my Nexus the GPS was the most sensitive I'd ever used. It would pick up a signal in many rooms in my house! It was after one of the core Android updated it seemed to lose some of its capabilities but can't pinpoint which.
 
airdale said:
What kind of airplane and where was the N7 held or mounted?

I flew right seat in a 182 a week or so ago and had trouble when my N7 was suction-cup mounted at the front of the side (door) window, a bit under the wing. When I moved the suction cup just forward of the door pillar onto the windshield the N7 got a better view of the sky and the GPS recovered. We were northbound so fewer satellites were probably in view.

I used the side window for mounting the N7 in a 195, which would seem to have the same wind-blocking-sky characteristic and had no problems. In this case we were flying approaches so the sky view varied quite a bit.
Click to expand...

C-150...and I even laid it up on the dash for periods of time. Just a slow blink on the GPS status.
 
LDJones said:
Nope...no case. Crazy thing is when I first got my Nexus the GPS was the most sensitive I'd ever used. It would pick up a signal in many rooms in my house! It was after one of the core Android updated it seemed to lose some of its capabilities but can't pinpoint which.
Click to expand...

I would return it. Either they send you a new one or you get your old one back.

Cheers
 
FWIW, the GPS antenna is on the back of the unit in the corner opposite the power switch. http://www.anandtech.com/show/6073/the-google-nexus-7-review/6 This review also says that the GPS is the same unit used in the iPad 2.

So face-up on the glare shield may result in something on the top side of the unit shielding the antenna's view of the sky or at least diminishing its sensitivity.

That said, I agree that the sensitivity I've seen playing with it (and with my departed iPad 2) around the house is amazing. But my house doesn't have a metal roof either.
 
Sorry for taking so long to report back on my GPS tests. There is something definitely not right with my Nexus GPS. I seem to have ruled out the positional errors but altitude still is much different than when I use my XGPS150.

Quick summary; I noticed some altitude differences between my iPad running ForeFlight & Garmin Pilot and my Nexus 7 running Garmin Pilot. On the Nexus, using the internal GPS antennae, I was seeing between 400 to 500 feet difference the altitude it reported versus what the iPad running Garmin Pilot with an external XGPS150 antennae.

I also suspected there were some issues with the GPS position reports as I saw on the georeferencing on both devices. To get to somewhat accurate answer to both of these concerns, I set up both units to determine what the differences were for both.

For the location tests, I set up the Nexus 7 with the internal GPS using Pilot and recorded the lat/long for the position I was at (stationary, on the ground). I did the same with XGPS150 antennae connected first to the Nexus and then to the iPad. Finally, I took the same information from my iPhone 5 running ForeFlight. I recorded results for the Nexus using Pilot with internal antennae, external antennae and using a GPS app for the Nexus (reports internal GPS function) and with the iPad running the XGPS150 with ForeFlight & Pilot. End result? The positions were essentially the same on all three devices.

The second round of location tests were done in motion, comparing my actual position to the georeferenced using the same combinations of devices, antennae and apps. Again, all reported the same information (essentially). I did notice a little bit of a difference with the Nexus running the internal antennae.

Altitude tests. I did a check on the ground at a known fixed point (airport reference). I did the same comparison using the different combination of devices, antennaes and apps. The result? The Nexus using it's internal antennae reported a ~150' difference (lower) than the other two devices and combinations -- both of which were within 20 feet of the known elevation (strange but true).

The tests were repeated at 2500', 4500' and 6500' feet. What I noticed was a significant difference at altitude. The higher I went with the Nexus using the internal antennae, the more deviation there was between what the other combinations reported. The Nexus with XGPS150 and the iPad with the XGPS150 were essentially the same using either ForeFlight or Pilot. At 6,500, the difference was almost 600'.

So, in a nutshell, there is something different about my Nexus internal GPS which is resulting in wrong altitudes being reported. At least the position reference is correct.
 
Could it be a software error? Are there OS-based computations performed on the GPS data before being passed on to the app??

No idea...just raising the question...
 
LDJones said:
C-150...and I even laid it up on the dash for periods of time. Just a slow blink on the GPS status.
Click to expand...

Weird. Sounds like a return to Asus may be in order. I'm running the latest OS, without any GPS problems.
 
You must log in or register to reply here.
Back
Top