Inaccurate distance posted
I just flew 2 missions, one started with an orbit that was too far for my drone so I had to walk to the area to complete the mission. I was almost directly under the drone and it said the distance was 688 ft.
The second mission was an "on the fly" follow and when I got back to my yard the drone was directly (fluorescent yellow) above me at 62 feet but the distance said 654 feet. Why?
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23 comments
Distance and altitude are both relative to the home point.
If I changed it to dynamic home port would that represent the distance from controller to drone? I noticed that I can click on dynamic in the follow mode but not when making an orbit.
Yes if you7 had it set to Dynamic home point it would represent the distance from controller to drone, however to have dynamic home point for anything other than follow mode, you need at least the growth plan
Bob Scheffler
Probably. If you are using your phone (it looks like you are) then, yes, because the phone has a GPS and knows where you are.
If using a wifi only device then then dynamic home point can be wildly off.
The distance reported has always been off since I started using about two years ago. Most of the time it is only anywhere from 60’ to 150’. I did notice very recently on one of my missions it was way, way off. Much worse then I’ve ever seen. I was going to wait to report this but since it is happening to you too I’ll just post on this thread. 3,319 and landing directly above me. Maybe this can be fixed 🤙🏼
Mike, I have not experimented any more with this because it was explained that the distance was based on the home base, not my location.
Mike
This is just a theory but...
If you are using a wifi only device then I believe that distance is an estimate of where you are that is based off a number of things such as cell towers in the area.
I make this assumption because I do a regular flight at a construction site. For that job, I have to relocate at one point for the last part. When I am on the site the location is relatively accurate - usually to within 50ft or so. But when I move to the second location it always places me about 3,500ft from where I actually am. I can see where it thinks I am and there is a huge cell tower there.
I am using a Samsung S21 phone. I do not even have the wi-fi turned on so it should be using GPS. I just did a little experiment. I took a definitive distance and tested it three ways. First I used a scaled Google earth, then the drone and finally the most accurate, a laser device that I use in civil engineering work.
Google Earth placed the distance between the 2 objects as 430 feet.
Drone said it was 464 feet
Laser said 420 feet
I did all three tests 3 times each, all were very close within each other, the laser was the most accurate, in 3 tests one test was off a tenth of an inch (I probably flinched while holding the device, the other 2 times I put it on a stationary device and both measurements were exact)
I trust the laser as very precise, it did cost $3,000. So that means the drone is off by 44 feet, that's a little less than 10% inaccuracy, not good in my book.
Mike when you were, supposedly, 3,319 feet away did you have a stationary home or dynamic? Barry explained that the distance is from the home base to the drone so if you move (like I did in my first report of this) it will show an extreme difference. In my testing I never changed the home base and it is still quite inaccurate. If you never moved then something is wrong. I am going to start paying closer attention to this situation.
Now I am even more confused. I started this post because the drone was on top of me but said it was 688 feet away. I created a spiral orbit so that each ring was a little further away. I walked to a ring where the drone would be flying to so the drone would be right above me, or as close as I could guess. I did this 4 times and each time the drone showed it was 15 to 20 feet away. So Barry this appears to refute what you were saying that the drone only reports distance from home base. If that is the case then what was my screen shot saying that I posted at the beginning of this post? Here are the 4 shots.
I never moved from my driveway. So the home-point is where I am landing it. Not using dynamic home-point. Can’t be a cell tower issue due to its a Wi-FI only device and doesn’t have anything to do with the drones GPS. The drones recorded home-point location which the app is using is the same as the DJI App which is always very close on both altitude and distance. The farthest distance away from home-point on this mission was about 2,100 feet so that’ strange? As I stated, I’ve Never seen it off this much before so thought I’d just mention it since Bob was having a similar issue. Not a big issue for me but it would be nice to have it more accurate for farther out missions like 2,000 so I know if I’m pushing the actual VLOS at a specific distance and not go too far out. The mission preview is close but actual missions are not always accurate.
Just remembered one other glitch I observed a month or so ago. Only happen once as far as I know so I didn’t worry about it. Mission at about 1,500 feet distance and all of the sudden the telemetry indicated something like 1.2 miles away, maybe more. Eventually it went back to correct distance. I don’t know If it is a DL or SDK issue or something else but it would be nice to get it corrected if possible. Very curious since the DJI App is always very accurate within a small amount on both distance and altitude.
There certainly seems to be something wrong. I am assuming that the Dronelink program should not be reporting distance in 2 manners. I have demonstrated that distance was measured 2 different ways. One: to takeoff point and Two: to RC point. I will try the same experiment with DJI Fly. Their manual says that distance is determined from home base just as Barry said. But now I am not really sure. Should be an easy test, just put the drone in the air and walk away with the RC, if distance stays the same it is calculating from the take off point. If distance changes then it is calculating from the remote.
Well that was an easy test. I used DJI Fly, launched and allowed it to mark home base and did not move drone. As I walked away (100 FT) the distance did not change. It did though say the distance was between 5 and 6 feet so it was inaccurate that much. I am not sure what Dronelink is using because it has reported it in both manners and I am not sure what it's criteria is when reporting distance.
I figured out the criteria. It depends on which dashboard you use. If you use the split screen one it reports the distance from the remote control. If you use the other (I believe it is called classic) then it uses home base.
Mike your issue is a little different than mine. Unless it is the same as the distance being incorrect by 10% only yours is multiplied because of the distance being 8 times mine. But I did my test with DJI and you were using Dronelink. I will have to work out a test for Dronelink.
At least I got one mystery solved.
Mike - the reason I believe my drone is using cell towers in that location is that I am using my phone as a wifi hotspot. That would not the be case if I were at home or connected to some other wifi
I Think some things are being miss-understood guys. The distance being reported should be from your launching home-point to the drone. All it knows is the GPS launched location to the drone which is recorded at take-off. DJI Fly app has always reported correctly within a very small amount of error which is expected. DL is way, way off. When I fly my 3 mile long missions while following the drone on my motorcycle it reports the distance from my launched location, not from my iPad or controller which is only about 200 feet or so away. The controller has no GPS so it would have no way of knowing how far from drone to it. If it can be checked somehow and corrected then it would be great. Obviously something has gotten way worse to be reporting 3,000 feet while at home-point landing and as much as and 1.2 miles when only 1,500 feet. I’m not going to worry about it but should be within reason. Enjoy guys.
On Android, the classic dashboard reports the distance from the drone to the home location, where the modern dashboard attempts to report the distance from the drone to the user location (using the location of the mobile device, not the RC). If the user location is not available, then it falls back to the home location. If the the mobile device is reporting a wildly inaccurate location, then this could be the cause. We may make this behavior configurable as a setting.
That explains a lot. Does that also mean in the follow mode it follows the phone and not the RC? If that is true that it follows the phone can a different phone be assigned the phone to follow? I assume the numbers used to report distance and altitude come from DJI because I did some distance testing and your distance was exactly the same as DJI.
So since I’m using IOS device and was using classic dashboard and I never moved from my driveway at the launched recorded home-point location, there is still some kind of an issue. 3,300 feet at landing can’t be correct no matter what. Also the 1.2 mile distance reported on another flight while only about 2,000 feet away. I’ll continue to see how it reports the distance but standing in my driveway should always be fairly accurate. I’ll keep an eye on it and see how much and how often it happens. Thanks for the info….
Let me know. I have never seen this (unless using a Wifi only iPad that has no GPS).
Ok Jim. It is a Wi-Fi only. No Internal GPS. However, when using the DJI Fly app it’s always very close on both. Whether I’m out in the remote Forest area or anywhere else without Wi-Fi It’s never been off by much and has been reporting the distance from drone to the home-point. DL has always been off a bit from 60 to 150 feet when landing at home-point which isn’t a big issue but now it’s way, way off. I’ll keep a close eye on it when I get a chance to fly a couple missions. My situation when flying with either app has always reported the distance from the drone to my recorded home-point. Majority of my flights are from my driveway at home. I checked Airdata and I believe it was either Beta build (218 or 219). I’ll keep you updated. Thanks Jim. 😃.
4.1 will have a new toggle so you can tell for sure:
Sounds great Jim. I’m guessing that will solve any issues using my iPad. I Just flew with the DJI Fly app with Wi-Fi enabled and then disabled at home. Both ways it reports zero altitude and distance before take-off. After landing using RTH it was 1 to 3 feet in distance and zero altitude. I Flew manually with DL both ways with Wi-Fi on and off and it indicated 114 feet before take-off and zero altitude. When it RTH the distance was the same 114 feet and zero altitude when landed. It’s always been a distance measurement which has been off. Not sure why it was so far of at least a could times but I’m not going to worry about it now. I’ll wait for the 4.1 and in the meantime I’ll just turn off the Wi-Fi after downloading mission for off-line. That should solve the issue. Still not sure why it has always been off by 60 to 150 feet or so on take-off. I would think it should be zero on both. Thank you for your help and as always keep up the great work. 😃
Also thanks Jim, this clears up the dual reporting of distance. It still does not explain the 64 foot difference which I am assuming is the quality of the hardware on the drone.
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