xgeek said:
Oh it's GPS plan for the iPhone
Thanks a lot for that. I downloaded it and it tells me that if I try to fly at 1:45 this afternoon, I won't have GPS available at all because there are only 5 satellites visible at that time.
A few minutes before that there are 6, I'll get a good home point set, fly off 1000 feet or so and my Vision+ will be a tiny dot in the sky. I can't see what direction it's pointed, heck, I can barely see what direction it's moving. The compass in my Nexus 7 isn't worth the powder to blow it to hell so radar on the vision app is no help. Now let's say there is a 10 mile per hour crosswind.
At this point I haven't done anything that violates any of Dji's recommendations. Now at 1:45pm, suddenly there are only 5 satellites visible. What happens?
1) Vision+ goes into ATTI. It acts like it has no clue where it is.
2) Vision app now says distance is "N/A" but still reports altitude.
3) "Find My Phantom Vision" just shows that last position when there were 6 satellites.
4) Home Lock won't work.
5) RTH won't work.
6) Vision+ is going 10 mph whichever way the wind is blowing.
The only way the Phantom isn't blowing away at 10 mph is if I can use the video feed to navigate my way back. I better be really good at this because in couple of minutes it may blow out of control range or wifi range.
I experienced this last night. I waited forever to get 6 satellites and a home position set. I'd start the motors, look down and distance was showing "N/A". Only 5 satellites. Wait longer until there are 6 and take off. Fly around for awhile until the thing figures out the magnetic declination, and then position hold won't work anymore. I look down and there are only 5 satellites again and the bird is in ATTI. The wind was only 1 or 2 mph, but if it was 10 or 15 (still within Dji's recommendations) and I was looking at the screen instead of the Phantom, that thing would have been out of sight over the trees within seconds.
I suspect that this is the Number 1 cause of "fly aways". I have done many hundreds of flights with R/C helis and quadcopters over the last couple of years. I might be able to recover from the scenario I mentioned, but it seems like the majority of these things are being sold to people with little experience and no sense of directional orientation. The chances of them recovering are pretty low.
Okay, here's the point: It makes a lot of sense to require 6 satellites before the Phantom establishes a home point. That's probably the minimum for a 10 foot or so radius home point.
It makes absolutely no sense for the Phantom to go into a Non-GPS mode at 5 satellites while it's in the air. With only 3 satellites you'll almost always have positional accuracy within 100 feet or so. That's good enough to get your quad back within visual control range with Homelock or RTH. But you're certain to get "fly aways" with 5 satellites the way it's set now.