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UPDATED! Studied, videos, My first flight/crash... and now I'm gun-shy to fly

My bad on 20m - meant 20'

How do you determine if GPS has a good fix or not - does it show how many satellites are active? I thought there was around 18.

It had 18 satellites and a navHealth level of 5, which is calculated from the estimated DOP (dilution of precision). But that's just a geometric estimate - it doesn't actually know what the error is. In this case it could see plenty of satellites but presumably was being confused by signal reflections that skewed the path lengths - always a danger without a good, direct sky view.
 
I'm just trying to figure out why the ac thought it was 20' south where actually was when I set the home point before takeoff? Are you saying that GPS is that inaccurate? BTW, the photo used is a Google earth but in real time there were no leaves on the tree, don't know if that would make a difference.
In the course I took last weekend, the instructor showed us that there's a little number next to the GPS signal strength. That was the number of GPS satellites the drone was utilizing. More satellites, better GPS accuracy. Fewer satellites, more GPS uncertainty. He said something like "10 is a good, strong number" to have - and we had like 18 in the parking lot where we were practicing.
 
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In the course I took last weekend, the instructor showed us that there's a little number next to the GPS signal strength. That was the number of GPS satellites the drone was utilizing. More satellites, better GPS accuracy. Fewer satellites, more GPS uncertainty. He said something like "10 is a good, strong number" to have - and we had like 18 in the parking lot where we were practicing.
Read the post above yours. In this case the OP had 18 satellites, but a GPS health of 5, not good enough for a solid determination by the FC.
 
In all of the 55 mentions of "Home" in the manual, it never says anything about auto-updating Home once the drone is in flight, and Home is a very important theme for the drones automated systems. Important enough that you probably shouldn't launch without it.
The manual is not exhaustive but there are people who have observed and tested to get a better and more complete understanding of how it all works.
The trick is to understand who actually knows what they are talking about and who is just guessing or repeating what they've heard from dubious sources and assume is correct.

In the flight in question, GPS conditions were poor (despite receiving signals from a good number of satellites) due to the tree cover blocking a lot of the sky view.
It had GPS and a rough position but the Phantom was not confident of the quality of the position fix.
The recorded flight data shows this message 2.5 seconds after launch:
Home Point Updated; Home Point recorded. Return-to-Home Altitude:213FT
That was when the Phantom got its the first good GPS position fix - the first one it was confident to use and that's what it recorded for its home point.

If the flight in question had a clear space around the launch point, it wouldn't have mattered that the recorded homepoint was a few metres away from the launch point.
That would have been close enough.
But tree cover where the home point was actually recorded meant that the drone wanted to descend into the trees.
An experienced flyer might have launched from that point and reset his home point above a clear area to prevent that.
He also wouldn't have allowed RTH to do the landing if it was in a tricky area.
Choosing a safe launch point (safe for landing) is probably more important than having the home point before launching.

Are you certain it'll automatically acquire a new Home while in flight if one wasn't available at launch? A test might require launching from a tinfoil covered box or something so the drone can acquire GPS after launch, but can't get it before launch.
I like to observe and test things.
I've had to fly from locations where there is no reception, so no home point recording and the Phantom records a home point when it gets good reception when it gets out in the open.
I've also seen flight data from flights by impatient Phantom owners that launched prematurely and their drones always record a home point soon after launch.

his position maybe isn't a bad one for a "beginner" flight class; it's just not entirely accurate. Looking for a good GPS return can help keep you from flying without a Home point, which many beginners may rely on as a safety net.

The instructor has been flying drones for years and may simply not have been aware of the systems being updated if he kept doing his routine every flight, he wouldn't have ever noticed a difference.
The home point/RTH system is just as it has always been since the first Phantom in 2013. It's never changed.
The information to unlock the mysteries is there in the app. DJI Go has been in use since early 2015 but ignorant myths are still out there and being spread.
Not understanding basics like how the drone records its home point suggests your instructor does not have an enquiring mind and is happy to repeat myths, assuming them to be correct when the evidence is easily seen in the app, flying experience and recorded flight data.
If you want myths, you'll find plenty in forums like this, but you should be getting accurate information from a professional instructor.
I would wonder what other myths he is teaching.

I think the DJI GO 4 software provides you with the option to create a new Home on the fly by saying "Home is where the Controller is" (assuming GPS on the RC - or maybe using the attached phone's GPS) or "Home is where you are right now" (using the AC's GPS).

I've been looking for an answer to that this morning, and the best I've seen is a reference to the software possibly tapping into a phone's GPS to establish that.
Here is where you can reset the home point to either the current location of the drone or the controller:
i-d5NL6cM-M.png
 
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I spent some time RTFM last night before I get my drone, and on page 15 it specifically addresses the "Home" function - and it says this about "Home" ...

In all of the 55 mentions of "Home" in the manual, it never says anything about auto-updating Home once the drone is in flight, and Home is a very important theme for the drones automated systems. Important enough that you probably shouldn't launch without it. Are you certain it'll automatically acquire a new Home while in flight if one wasn't available at launch? A test might require launching from a tinfoil covered box or something so the drone can acquire GPS after launch, but can't get it before launch.

Your quote from the manual says it all...
DJI Mavic 2 Manual said:


If a strong GPS signal was acquired before takeoff, the Home Point is the location from which the aircraft launched.

Being that there is not a good enough GPS Signal, the homepoint may not be recorded at launch. However, when a good enough GPS Health is achieved, the home point is recorded. That could be some distance away from launch. To correct something in your comment above, this is not a NEW homepoint, but the first home point recorded in that flight.


I think the DJI GO 4 software provides you with the option to create a new Home on the fly by saying "Home is where the Controller is" (assuming GPS on the RC - or maybe using the attached phone's GPS) or "Home is where you are right now" (using the AC's GPS).

I've been looking for an answer to that this morning, and the best I've seen is a reference to the software possibly tapping into a phone's GPS to establish that.

I promise I'm not trying to be a know-it-all. I haven't even held my drone yet, let alone flown it. I am, however, trying to learn as much as I can about the systems involved before I ever launch. If it seems like I'm challenging answers or speaking in ignorance, it's not intentional.

Should your phone have a gps, then yes, you could use dynamic HP in active track, or side swipe your screen and select the controller as a new homepoint.
However, the initial RTH homepoint is set by the AC, assuming that it has sufficient gps health.
 
Read the post above yours. In this case the OP had 18 satellites, but a GPS health of 5, not good enough for a solid determination by the FC.

What would be good enough GPS health? and the "5" referenced -is this on a scale of 1 to 10?
 
FWIW, when I set the home point it was based on where the AC was sitting (on launch pad). it was mentioned the drone may look at area to fix a point. Keep in mind it said I had set the home point before I ever took off. Also, I am using a Samsung tablet with ONLY wifi - and I do not have wifi at my home so it is only using it for display/app. I am assuming the AC is being controlled by RC from the controller as it would not have the option of syphoning off the data/gps from the tablet?
 
FWIW, when I set the home point it was based on where the AC was sitting (on launch pad). it was mentioned the drone may look at area to fix a point. Keep in mind it said I had set the home point before I ever took off. Also, I am using a Samsung tablet with ONLY wifi - and I do not have wifi at my home so it is only using it for display/app. I am assuming the AC is being controlled by RC from the controller as it would not have the option of syphoning off the data/gps from the tablet?

If the tablet has gps, it could be used if you were to change the Home Point to where the controller is located. If a device does not have a gps (some ipads for instance), then the home point could not be set to the controller's location.
 
FWIW, when I set the home point it was based on where the AC was sitting (on launch pad). it was mentioned the drone may look at area to fix a point. Keep in mind it said I had set the home point before I ever took off. Also, I am using a Samsung tablet with ONLY wifi - and I do not have wifi at my home so it is only using it for display/app. I am assuming the AC is being controlled by RC from the controller as it would not have the option of syphoning off the data/gps from the tablet?

I'm not clear what you mean by "I set the home point...". The home point is set automatically by the aircraft, using its GPS system, when it takes off. The visual survey that it can do is only to enable the precision landing option - it's not involved in recording the coordinates of the home point.
 
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FWIW, when I set the home point it was based on where the AC was sitting (on launch pad). it was mentioned the drone may look at area to fix a point. Keep in mind it said I had set the home point before I ever took off. Also, I am using a Samsung tablet with ONLY wifi - and I do not have wifi at my home so it is only using it for display/app. I am assuming the AC is being controlled by RC from the controller as it would not have the option of syphoning off the data/gps from the tablet?
Your drone recorded a home point initially but knewit was inaccurate.
That's why it updated when it got a better gps signal 2.5 seconds later after you had launched.

The tablet's gps is not used as the position of the drone is what's important.
 
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I'm not clear what you mean by "I set the home point...". The home point is set automatically by the aircraft, using its GPS system, when it takes off. The visual survey that it can do is only to enable the precision landing option - it's not involved in recording the coordinates of the home point.

Well, in the app there is a setting for either "set the homepoint to where the AC is or use the controller location" remember, this is the M2Z - not sure if maybe you have a different AC and do not have these options?
 
Well, in the app there is a setting for either "set the homepoint to where the AC is or use the controller location" remember, this is the M2Z - not sure if maybe you have a different AC and do not have these options?
You didn't set the home point (and you don't need to).
The Mavic does that for you automatically.
But in your case It was in a spot where it couldn't get a good GPS signal to get a good location fix because of the tree cover blocking the sky.

All DJI drones record their home point the same way.
 
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Well, in the app there is a setting for either "set the homepoint to where the AC is or use the controller location" remember, this is the M2Z - not sure if maybe you have a different AC and do not have these options?

There is a function in the app to reset the home point to the location of the mobile device - provided that the device has GPS. That's not a blanket setting to make the controller the home point. In any case, as @Meta4 mentioned above, the home point was set by the aircraft at 2 s, after takeoff
 
I have had my Mavic Air go more or less brain dead near my house twice. It could be my poor flying but I really don't think that I'm to blame and I wonder if having sensors at both front and back could have something to do with it. It has never happened in an open area but then again it has never happened in the same place with my spark and I fly that from the very same spot. I used to practice flying my Phantom 3 in ATTI mode in swirling gust winds near my house and even though I can't say I'm great at it..my Air didn't seem the same when I lost control of it. I fly my Spark in the house with the phone all the time..it's always very steady....I'm not but it is.. Take your drone to a more open area and you'll get your confidence back
happy flying
 
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Well, in the app there is a setting for either "set the homepoint to where the AC is or use the controller location" remember, this is the M2Z - not sure if maybe you have a different AC and do not have these options?
Your post raised a question for me: If the controller location is selected for the homepoint is this a static location, or does it move when the controller is moved while you’re flying?
 
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Your post raised a question for me: If the controller location is selected for the homepoint is this a static location, or does it move when the controller is moved while you’re flying?
The wording for the options for resetting home is the current location of the aircraft or the current location of the controller.
Once updated, it does not continue updating if the aircraft/controller moves.
 
Re being "gun shy": I'm guessing there are very few drone pilots who've never crashed - or at least come close enough to crashing that it made them a bit leery about getting back on the horse that [almost] threw them. My advice is the same as Meta4's -- Find a large area with no trees and fly to your heart's content. Then come back here and share what fun you had - and maybe post photos and/or vids, too. Enjoy your Mavic 2 Zoom - It's an amazing flying machine.

Crashes? --- Check out these videos, then get back on the horse: https://mavicpilots.com/threads/mavic-crashes-other-unfortunate-events.60646/
 
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I had a series of drain pipes buried in a 40 acre field without trees. I thought I could use the drone's gps location as it flew a few feet over the buried pipe with the camera straight down to map the pipe locations for future reference. I did it 3 times - each with 15 + satellites and found that the gps locations varied as much as 14' from flight to flight. That was with a Spark. With both the Spark and Pro - on RTH - loading on a large black paved surface without a landing pad ie no visual guidance help - it often is coming down 5' from the Home point. So just from my observations - I don't trust gps to an accuracy of better than 10-20' (I round up for safety). I think the controller giving distances to a tenth of a foot overstates the accuracy of the gps coordinates.

In your case under trees made the accuracy worse.
 
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None of this applies to this situation - I had put a maximum height of 213 feet and then went straight up and straight down never changing trajectory off of The Landing Pad vertical axis as well as operating in beginner's mode so something else was going on. But thanks for posting the info
Jake,

Where do you live? If anywhere close to Atlanta, Thunderdrones flys frequently in Duluth. I live close by and do the same. Perhaps (-While you're waiting for parts) you could fly with another drone pilot. You'll learn a lot that way.

I agree that flying off or around a deck is a poor choice for a beginning location. There's just too much to hit. A big pasture is better. Even after many hours, I would not choose a patio/deck launch area. -I have when it was necessary, but my choice would be to NOT fly from there.

I've not had the bizarre reactions that you've had. When I was new though, I DID fly into a bush while flying backwards. I was lucky and only had to replace props.
 
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