Bogus Flyaway Theory #85

[ianwood]

It seems a lot of P2V flyers are watching this, which is too bad because it's wrong:

[youtube]https://www.youtube.com/watch?v=_ge3GuhEDRM[/youtube]

 

[HailStorm]

Could you possibly expound on "it's wrong?"

It seems a plausible explanation for some flyaways.

 

[p fandango]

if his "theory" of the home point being set upto 14mile away, would it not display a message on the screen when it thinks its outside of its radius limit before flying off

 

[ianwood]

To start with, they don't seem to understand how GPS works.

 

[hemorrhagic flyer]

To start with, they don't seem to understand how GPS works.

...or cell phones.

The "when you open Google maps on your phone" example is preposterous. The initial fix that is fourteen miles away is rough location based solely upon data from the cell phone towers. The second, correct fix, is GPS location.

 

[HailStorm]

Thank you. These explanations are much more educational (at least for slow learners such as myself) than simply reading that something is wrong without any further explanation.

 

[crash1sttime]

i saw that video whilst trawling thru youtube, one of the comments was " why dont you just check using find my phantom, which seems an idea, i kind of get the idea of what he is saying as my home point according to the waypoint app using my samsung s3 can sometimes be 20ft from the point im stood at, but 14 miles is a bit of stretch.

incidentally does anyone have a phone that shows their exact location to within a foot when using it?

 

[justin00]

Mine gets incredibly close, but I live in the innter suburbs and there are a number of cell towers near me..
The cell location pin points me where abouts I am in my 3 story apartment block.

Also my phone GPS is more than accurate than the Phantoms GPS even if it has 8 or 10 satts.. The phantom isn't to bad at all, but the phone just gets closer.

 

[ianwood]

This is what I wrote in response to the video 5 months ago:

11,000+ views and this couldn't be any more wrong. Your home location is recorded with 7 or more satellites acquired. With 7 satellites, your PDOP will be below 4 and at most a 5-10 meter positioning error on a bad day. More typical is around 2-3m. And what makes this video even worse, is that a GPS error tends to stay consistent over short periods of time due to the gradual change of atmospheric conditions. GPS jumps do happen but typically only when in areas where significant portions of the sky are obscured or when sudden geomagnetic impulses (K index >5) are experienced. Sometimes, it's a satellite low on the horizon but the jumps are small unless you have less than 7 SVs locked in.

You'll find that the majority of fly aways are actually mechanical failures or related to a bad compass calibration, taking off on or near magnetic materials, moving the Phantom during IMU initialization, creating or being exposed to strong RF interference. 

As for your phone, it's not a fair comparison. Your phone is pulling in a lot of other non-GPS data to figure out where it is. Meanwhile, the Naza GPS has to download the almanac and ephemeris the old fashioned way.

 

[Monte55]

If you want to confirm your home location...fly out a hundred feet, select Homelock with S2 switch...pull back on right stick. It should come back to you. When it gets within about 30 feet it will twitch as it changes to Course lock. What is so hard understanding that?

 

[ianwood]

If you want to confirm your home location...fly out a hundred feet, select Homelock with S2 switch...pull back on right stick. It should come back to you. When it gets within about 30 feet it will twitch as it changes to Course lock. What is so hard understanding that?

Does the Vision app not tell you the distance, height, azimuth from the home point? The P2 OSD shows them and so you can skip doing anything with home lock just by looking at the screen.

 

[Meta4]

Here's what the app shows - all of that stuff + a radar display showing where and which way your Phantom is pointing.

 

[csauer52]

incidentally does anyone have a phone that shows their exact location to within a foot when using it?

Mine is pretty darn close. Well within a 4' diameter anyway. Samsung Galaxy S5.

 

[4wd]

I don't think information from cell towers can help much (on the phone) because here there is no coverage but it can still show the right room in the house.
If you leave it showing on google maps or whatever it will wander about some though.
Still rarely more than 30 feet out.

I usually use the find my phantom feature.
It doesn't matter if the map is very low res so long as the red pin and blue circle are together (phone and phantom)

You do still see video from time to time where people apparently aren't letting it get a home fix and in that situation it might try to go back to the last logged home point.