Dirty Bird said:
#1 is an interesting question, for which I do not have a definitive answer. To my knowledge, the Home Point location is NOT saved, however, there IS a small battery on the GPS board photos I have seen. This battery may be used by the GPS exclusively...perhaps for an onboard clock, or to maintain ephemeris data? Personally, I would want to allow the Phantom to obtain a new Home Point each and every time you fly. Else, what if you are flying in Kansas today, but flew in Maryland yesterday. Its gonna open up a big case of "SUCK!" if she decides to fly home to yesterday's Home Point! :shock:
2 - Since I do NOT believe the Home Point is retained through power cycles, it means you won't have ANY Home Point, and you will be utterly homeless. Wait for enough satellites to set a Home Point ***BEFORE*** you take off!
3 - If there is no Home Point set, I am not sure how she will behave. Will she just "land only" where she is, or fly to some undefined Home Point? You might want to peruse the user manual a bit and see if these scenario is defined?
I apologize for not having a definitive answer. I strongly suggest you ALWAYS achieve a fresh satellite lock, with a bare minimum of 6 (preferably 7) satellites locked. Its an expensive gadget to lose.
#1 - Just to be clear, the Home Point is definitely
not saved when the power is shut off. You're right about the battery on the GPS board. It's there to keep satellite data in battery backed RAM when the main power is off. Unfortunately the batteries tend to be dead on arrival. It's supposed to be between 1.8 and 3.0 volts. When I checked, mine was 0.014 volts. The battery is spot welded in place so not easily replaceable. I think there is a slim chance it's some sort of rechargeable battery intended to backup GPS RAM for a couple of days, but I doubt it since I had flown the day before I got the dead reading on the battery.
#3 - Yes, with no Home Point set, it will start down from the point the control signal is lost. If there's no wind or if it has acquired the minimum 6 satellites after takeoff it will go straight down. In a wind, if it's currently seeing less than 6 satellites, it will be blowing downwind while descending.
There is a corollary to point #3. Even if you had 6 satellites and a Home Point set before takeoff, if it drops to 5 or less visible satellites the Phantom goes into "Ready to Fly non-GPS" (which is identical to ATTI). In even a fairly mild wind, if you're looking at the screen instead of the bird, that thing can be a long way off before you notice and can respond. I've seen this happen but I caught it before it was out of sight over some trees - just barely.
I personally think the default "Phantom Mode", with different names for identical flight modes than what they are called in "Naza Mode", just creates unnecessary confusion. The assumption on DJI's part, that new buyers of these things are too dumb to follow an instruction like "Put both switches in the Up position" is ridiculous. That is exactly the same thing as "Phantom mode", but with more control options to get yourself out of trouble.
Well actually there is one significant difference between "Phantom" and "Naza". The LED flashes while flying are different so you have to download another manual just to find out what those mean.
I sympathize with those who have read the manual, and have difficulty sorting out things like the difference between "Tx", "Remoter Controller" and "Controller" (Hint- they are the same thing). I had the same problem and this isn't my first rodeo.