Good morning DJI friends and users:
I have a question regarding the D-RTK base station unit.   We are a Surveying and Mapping Division and we are Surveyors looking to do precise mapping with our M600 Pro, Zenmuse X5R, and DJI's D-RTK Unit.   As previously mentioned, setting ground control points and targeting them is what we do, so we plan to have our D-RTK base reside over one of our control points as a base station.

My question is, and I've been looking in the base station specs, etc., but is there an offset from the phase enter of the base RTK antenna to the center of the plate, namely the screw hole that will sit atop the tripod resting over our control point?

Do we place the actual Antenna head directly over the ground control point with a plumb bob, or do we screw the base station plate into a tripod and place the center of the tripod over our known control point?  If so what is the offset from the phase center of the antenna to the center of the plate?

Any assistance would be greatly appreciated.

Thank you,
Alex W. Parnes, PSM
County Surveyor
Pasco County, Florida.

I am also wondering the same information Alex, have you gotten any response to this?

Vashaun@Rekon Posted at 2018-2-11 16:20
I am also wondering the same information Alex, have you gotten any response to this?

No response yet Vashaun.   Hopefully they're researching this.  They are definitely not Surveyors so they probably don't understand exactly what I'm asking.  Stay tuned and if I hear something I'll forward it to you.

1.What is the D-RTK?
D-RTK is a high-precision navigation and positioning system that integrates advanced software algorithms with a GPS+BDS or GPS+ GLONASS dual-band, four-frequency receiver. The D-RTK system is compatible with a range of airframes, and gives the equipped system centimeter-level positioning accuracy both horizontally and vertically.

On the product page, it speaks specifically about using with airframes. I would not alter from this point regarding this unit.

DJI-Mark Posted at 2018-2-12 10:12
1.What is the D-RTK?
D-RTK is a high-precision navigation and positioning system that integrates advanced software algorithms with a GPS+BDS or GPS+ GLONASS dual-band, four-frequency receiver. The D-RTK system is compatible with a range of airframes, and gives the equipped system centimeter-level positioning accuracy both horizontally and vertically.

Thank you DJI Mark. I appreciate your reply, D-RTK, and GPS definitions.  My actual question was regarding the actual phase center of DJI's D-RTK GPS base station antenna.  Generally the actual phase center (the zero position where all the pseudoranges from the GPS satellites converge) is actually somewhere in the antenna dome.   Now, what interests Surveyors and Mappers, because we require real world Absolute precision and accuracy on the real Earth or ground, not only relative precision, is ....what is that distance from that antenna phase center to the center of the base plate where the tripod attaches?  You see, that spot on the bottom of the plate will actually be over a designated point on the ground, you call them GCP's or Ground Control Points.   We require this offset so we can calculate the actual position on the ground and not just to the antenna phase center.  This way we can place a target on the ground and use it for Photogrammetry control on adjusting our data.    I hope I explained my question.  Sorry for the confusion.

Thank you,
Alex W. Parnes, PSM
County Surveyor
Pasco County, Florida

PascoCounty SAM Posted at 2018-2-12 10:29
Thank you DJI Mark. I appreciate your reply, D-RTK, and GPS definitions.  My actual question was regarding the actual phase center of DJI's D-RTK GPS base station antenna.  Generally the actual phase center (the zero position where all the pseudoranges from the GPS satellites converge) is actually somewhere in the antenna dome.   Now, what interests Surveyors and Mappers, because we require real world Absolute precision and accuracy on the real Earth or ground, not only relative precision, is ....what is that distance from that antenna phase center to the center of the base plate where the tripod attaches?  You see, that spot on the bottom of the plate will actually be over a designated point on the ground, you call them GCP's or Ground Control Points.   We require this offset so we can calculate the actual position on the ground and not just to the antenna phase center.  This way we can place a target on the ground and use it for Photogrammetry control on adjusting our data.    I hope I explained my question.  Sorry for the confusion.

Thank you,

I can see if I can get you some additional information. Can you send me a personal message?

DJI-Mark Posted at 2018-2-12 12:37
I can see if I can get you some additional information. Can you send me a personal message?

DJI-Mark,

What was the outcome of this inquiry?
There are more here than you may realize that are in need of this information - very useful.
Could you please reply to the forum so that everyone is on the same page once you have an answer?

Thank you.

MT>

I concur with djiuser_KFAyx3sFSGsl, we'd like to know the answer

DJI... Your answer to this question is absolutely required... If your D-RTK product would like to enter the Absolute Accuracy business.

The Antenna

Hi Alex,
If I understand you correcly.....then you want exact georeferenced pictures with your M600 Pro, Zenmuse X5R, and DJI's D-RTK Unit? If so....you can forged the phase center offset. If they don´t correct the offset you have a failure about a few centimeter. But the accurancy how the base center measures the coordinates is about meters, because the base station can get only the coordinate over a code solution. The high accurancy from the D-RTK is only between the base station and the M600.
The only thing you can do is to measure the position with an another GPS-system with correction data and put this coordinates in the base station. We use a Leica GPS system and use the DJI antenna directly. But we have modified the plate a little bit.    

Kind regards
Holger

Did anyone ever get an answer from anyone with DJI as to this answer?

My understanding is that the RTK implementation in the pre-M200 V2 series Matrice units is not fit for survey-grade photogrammetry as the aircraft RTK positioning information is not calibrated to the image sensor center, and the RTK position is not recorded in the EXIF data.

The RTK position is used for improved navigation only. No image geolocation improvement is gained.

The P4RTK and M200 V2-series, together with the D-RTK 2 base that DJI is selling now have made strides in that direction, but still leave a lot to be desired for those of us that are used to surveying and the tolerance, documentation, and robustness of equipment we trust.

666mille Posted at 2018-9-6 00:11
Hi Alex,
If I understand you correcly.....then you want exact georeferenced pictures with your M600 Pro, Zenmuse X5R, and DJI's D-RTK Unit? If so....you can forged the phase center offset. If they don´t correct the offset you have a failure about a few centimeter. But the accurancy how the base center measures the coordinates is about meters, because the base station can get only the coordinate over a code solution. The high accurancy from the D-RTK is only between the base station and the M600.
The only thing you can do is to measure the position with an another GPS-system with correction data and put this coordinates in the base station. We use a Leica GPS system and use the DJI antenna directly. But we have modified the plate a little bit. [view_image]   [view_image]

Dear 666mile,
We are trying to do the same as you. We have high precision measurement of the ground point under RTK base station. But when I enter the coordinates (adjusted for antenna height) in DJI assistnant connected to base station RTK nothing happens, there is no button to save this coordinates.
How did you update the base station coordinates?

djiuser_xjZNrbSay843 Posted at 6-7 01:29
Dear 666mile,
We are trying to do the same as you. We have high precision measurement of the ground point under RTK base station. But when I enter the coordinates (adjusted for antenna height) in DJI assistnant connected to base station RTK nothing happens, there is no button to save this coordinates.
How did you update the base station coordinates?

I reply to my own question.
My problem was I was configuring the base station indoors and LED was red. Once I went outside and the station got a green LED meaning a satellite fix, I  was able to connect with a laptop and a dji assistant 2 software and finally connect D-RTK to configure the coordinates, set fixed reference station coordinates. This is done simply by filling the boxes and hitting enter on the PC keyboard.
Coordinates must be in decimal degrees, just numbers without N,S,W,E or any letters. North and East are positive.
The altitude does not seem to be of geoid, but of mean sea level.
This is also based just on trial and error, hope it helps smbdy.

Hey there,

We also faced the problem that the antenna is mounted off-centered on the ground station. Therefore we created this mount which can be 3D-printed or CNC-machined to be able to put the ground station on a known point using a Tripod. We still don't know the height of the antenna phase-center though.

You can get the mount here: https://www.thingiverse.com/thing:3686577



Hope it helps!