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Configuring RTK base with DJI Assistant 2
3332 11 2017-3-20
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Ramiro_Vigo
lvl.1

Spain
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Hello,

I think there is a bug here:

When you configure DJI D-RTK (ground segment) it asks for "elipsoidal height" (without saying what datum and coordinate system)

I used a Trimble R8 GNSS GPS with the following measurements for the DJI D-RTK Base:

Lat: 42.16877139 N
Long: -8.68799987 W
Height: 523.294 m (elipsoidal WGS84)

With this good coordinates from Trimble GPS, the RTK is blinking all the time: red and green (not fixed).

But If I get the same point coordinates from Google Earth (not very good coordinates) like this:

Lat: 42.1669960
Long: 8.686421
Heigh: 456 m


Then  D-RTK works, the LED is "FIXED GREEN" (it Works).

But as you can see there is a big difference: 523.294 - 456 = 67.294 m

My questions are three:

(1) Is not very dangerous to Land or use waypoint with Google Earth coordinates in the D-RTK base since there is 67 m of difference?
(2) What datum and system is asking DJI Assistant 2?
(3) Why the DJI GPS (D-RTK ) is not accepting real and true GPS coordinates (WGS84) from a good Trimble GPS,
     but it is accepting not very good Google Earth coordinates?


Best regards,

--
Ramiro Alvarez Clavero
Remote Sensing Service
http://gravatar.com/ramalvclav
Center for Support of Scientific and Technological Research (CACTI)
Vigo University
2017-3-20
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JackOO7
lvl.1
Flight distance : 2280 ft
Finland
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Very good question indeed.
2017-4-22
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JackOO7
lvl.1
Flight distance : 2280 ft
Finland
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Very good question indeed. Any answers from dji?
2017-4-22
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Ramiro_Vigo
lvl.1

Spain
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JackOO7 Posted at 2017-4-22 13:15
Very good question indeed. Any answers from dji?

No, I reported this problem lots of times but DJI has not answered, this is a proof of the bad technical support offered by DJI in this forum.
2017-5-25
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rick.iseeit
lvl.2
Canada
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Ramiro_Vigo Posted at 2017-5-25 23:22
No, I reported this problem lots of times but DJI has not answered, this is a proof of the bad technical support offered by DJI in this forum.

Hey Ramiro,

Question...
The D-RTK is plugged into the A3 so does that mean that the A3 will fly with 1cm precision or does the RTK only provide precision data to the camera?

I just started flying a new M600/Pro with RTK and my return-to-home was about 5 feet off the home.
I had GPS was 15 with a blue R.
2017-6-8
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EagleDrone
lvl.1
Flight distance : 168149 ft
Netherlands
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rick.iseeit Posted at 2017-6-8 16:41
Hey Ramiro,

Question...

D-RTK does not geotag the pictures. I did hear that DJI is working on it, but those rumours are already 6 months old...
2017-6-13
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rick.iseeit
lvl.2
Canada
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rick.iseeit Posted at 2017-6-13 12:09
RE:
Question...
The D-RTK is plugged into the A3 so does that mean that the A3 will fly with 1cm precision or does the RTK only provide precision data to the camera?
I just started flying a new M600/Pro with RTK and my return-to-home was about 5 feet off the home.


DJI support replied with the following:

"Our RTK provides more accurate positioning when flying and hovering, but when you get it return it to home (RTH button), the drone doesn't use RTK, but just uses its GPS."
I'm happy with that.

The infrared camera that I am currently testing HAS written code (SDK) to get the GPS info from the M600/Ronin-MX to the camera.
I'm not going to mention their name because I'm waiting for them to response satisfactorily to my recent purchase before I start promoting their solution.
Long story.
2017-6-13
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Adam_Geomatics
lvl.1

Australia
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Hi,  KlauGeomatics has announced a new PPK GPS technology for accurate aerial surveying using DJI drones without placing ground targets. See https://www.veritypositioning.com/ for more details.
2018-1-4
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prodaja.rcsrbija
lvl.2
Flight distance : 9967215 ft
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Serbia
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Hi, so far is pretty clear that DJI don't have surveying in their minds when it comes to the RTK, but never the less, does anyone know, including the DJI guys, what is the refresh rate of the D-RTK GNSS?
2018-2-14
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davidherries
lvl.2
Flight distance : 3767487 ft
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New Zealand
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Hi

Within the DJI D-RTK Base Station I can set a known set of co-ordinates as shown here.   I agree this is a very good question, in that what Ellipsoid does DJI use for altitude ?  Any further discussion and ideas on this topic  


Also now that I have this absolute location of the base station has anyone done testing on the resulting RTK photo positions.   Note we know that these are not being stored to the EXIF, but it looks like they are available in the log files, so just wondering if anyone has done some post processing to link the log files with the photo's.

Thanks
Dave


2018-10-7
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Felix Wolter
New

Germany
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The answer on the questions rised in this post also interest me alot. Do anyone has experience if this function is further developed in the new Phantom 4 RTK + Base set?

Thanks,
Felix
1-10 02:27
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djiuser_vizBkUXxbxxT
lvl.2

United States
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Ramiro, there is no bug. You are trying to plug in an ellipsoidal height (measured from the reference ellipsoid) when GS Pro is asking for an altitude. Since altitude references sea level, you need to reference an orthometric height (or elevation from sea level). The orthometric height uses differences between the geoid (sea level based and gravity) and the ellipsoid (calculated, true earth center) to calculate elevation.

Process your trimble data to elevations, not ellipsoidal heights. The reason your google earth works is because it is close (plus or minus) to the elevation of the take off point. Thankfully, most gnss software knows when you're way off, and just doesn't work.

On another note, these forums are designed to help people. Please keep comments relative to the original post.

Your neighborly professional surveyor.
4-5 13:47
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