GoPro Forums banner

1 - 11 of 11 Posts

·
Registered
Joined
·
18 Posts
Discussion Starter #1
I did a GoPro video of a flight that was 3.5 hours long. Our filed altitude was 34,000 and according to the flight tracker we stayed pretty much around that.


I'm overlaying the GPS gauges using Dashware. On the ground at the Atlanta airport, the displayed altitude was pretty close to what that airport is officially measured at based on the FAA chart field elevation, so can I assume that the GPS is measured at sea level? (MSL) Because the FAA aviation chart would show sea level altitude of the airport. Well, over the duration of the flight the GoPro GPS started out at around 35,000 once we leveled off, and 2 hours later it was up to 36,200 feet. Once we landed in Phoenix, again my GoPro GPS is very close to what the FAA chart says that airport is. So why would the altitude have crept up over the duration of level flight when our official altitude stayed the same? Was it recording at ground level (AGL) and not MSL?
 

·
Banned
Joined
·
118 Posts
GPS and other similar systems are not very good at height compared to horizontal movement.

What is your positional accuracy (CEP) for the video? I see around 1 meter for the HB6. Two (2) meters plus slower and more fragile locking for the HB7.

When GPS gets funky speeds and distances tend to vary higher based on my logging. I see the same for altitude looking over some logs, but this is at ground level.
 

·
Registered
Joined
·
18 Posts
Discussion Starter #3
Another strange quirk I found is that while on the ground and at low speeds, the heading direction readout swings wildly all over the place. But once the plane starts rolling and getting fast it locks in and is fairly accurate - i.e. rolling on runway 9 and it shows 90 degrees - and it only tends to move with the plane. So why so inaccurate when standing still?
 

·
Administrator
Joined
·
9,158 Posts
Have you factory reset and reloaded firmware that will correct gps gopro said.
 

·
Administrator
Joined
·
9,158 Posts
think it does fine to say hey look but if I had to rely on it for accuracy I get a real unit.

 

·
Banned
Joined
·
118 Posts
Another strange quirk I found is that while on the ground and at low speeds, the heading direction readout swings wildly all over the place. But once the plane starts rolling and getting fast it locks in and is fairly accurate - i.e. rolling on runway 9 and it shows 90 degrees - and it only tends to move with the plane. So why so inaccurate when standing still?
GPS is not very capable at low speeds as far as positioning goes. But it likes that for getting the best lock for use later on. For standing still the accelerometers are the way to go but this requires firmer mounts than gopros need for clear video. So to get best speed readings u need more than one way to measure, and then some math. Some phones use 2 or 3 different GPS systems such as Glonass, Waas to assist US GPS, Galileo etc. Then they triangulate off of wifi, cell towers and some say, other users.

It helps immensely to look at the raw data recorded into the videos using special software. You want the camera level, near a ground plane and sitting stationary with a 360 view of the sky. Inside something like a car or plane with metal skin and EMI it gets much trickier.

I can certainly see why some report funky maps, speeds and so forth using the GoPro Quick app. Some of that can be fixed with other software or via firmware. GoPro activates different GPS arrangements depending on which part of the world you are in. For instance in the S hemisphere Glonass (Russian based) is not very good. So a GPS (worldwide) plus Glonass (northern part of northern hemisphere is best for Glonass) setup down under will revert to just GPS.

There's a lot to this topic.
 

·
Registered
Joined
·
18 Posts
Discussion Starter #8
I was looking at my data compared to the flight log data stream provided by the flight tracker, Flightaware. I found that once the plane got moving, positioning locked in and was actually within a degree of what Flightaware has, which comes to them from the plane's ADSB data stream so its accurate. I also found the speed to be very accurate, only a couple mph off, of course the goPro posted mph and I converted to knots by dividing by 1.151 but That compared to the knots shows on Flightaware was pretty **** accurate. The only thing that wasn't was the altitude.


Also, GoPro's software does a horrible job at GPS. I used Dashware to extract and display the gauges. GoPro showed a loss of data on two of the clips, but Dashware showed them. Funny thing is, neither one was able to find any GPS data in the first leg of my flight which was on an older MD-80 aircraft. I wonder if that had anything to do with it.
 

·
Registered
Joined
·
2 Posts
The GPS was accurate, your assumption was not. Above 18,000’, planes fly at a constant pressure altitude of 29.92. As the local barometer goes up and down, so does the plane, thus it’s true altitude is not fixed but constantly changing. This keeps all the planes separated vertically without needing to change the barometer setting on the altimeter ever 10 minutes.
 

·
Administrator
Joined
·
9,158 Posts
thanks . always a great shot when flying
 
1 - 11 of 11 Posts
Top