Can anyone tell me the offsets from antenna to camera for PPK processing?  Since there are two antennas, I assume one is the main and the other is backup?  For drones with a single L1 or L2 antenna, the offset is a no brainer but I am trying to figure out what the offset shouild be for the M300.

Hi, there.
Sorry for the late reply.
We will confirm with the relevant team and reply to you asap.
Thank you for your support.

Update:
Sorry for the late reply. Hope the following information can help you:
1. If you are using a Zenmuse P1 camera, you can refer to the Timestamps.MRK file generated by the camera. There are fourth, fifth and sixth lines in it, which represent the compensation value from the camera to the antenna position. You can fill in this value for PPK;
The fourth column: the deviation of the antenna phase center to the camera CMOS sensor center in the north direction (N) at the moment of exposure of each photo, the unit is mm, the CMOS center is positive in the north direction of the antenna phase center, and negative in the south direction.
The fifth column: the deviation of the antenna phase center to the camera CMOS sensor center in the east direction (E) at the moment of exposure of each photo, the unit is mm, the CMOS center is positive in the east direction of the antenna phase center, and negative in the west direction.
The sixth column: the deviation of the antenna phase center to the camera CMOS sensor center in the vertical direction (V) at the moment of exposure of each photo, the unit is mm, the CMOS center is positive when the antenna phase center is below, and negative when it is above.
2. If you want to measure manually, please refer to the following information: The main antenna is the center of the RTK antenna mushroom head of the aircraft's No. 4 arm, and the compensation value data (the center position of the gimbal interface of a single gimbal is relative to the position of the No. 4 RTK antenna) ):
X-axis direction: 443.37mm
Y-axis direction: 333.63mm
Z-axis direction: 91.13mm

DJI Natalia Posted at 10-9 20:01
Update:
Sorry for the late reply. Hope the following information can help you:
1. If you are using a Zenmuse P1 camera, you can refer to the Timestamps.MRK file generated by the camera. There are fourth, fifth and sixth lines in it, which represent the compensation value from the camera to the antenna position. You can fill in this value for PPK;

Thank you Natalia!  That was exactly what I needed and very helpful!  

FlyinLo Posted at 10-9 20:59
Thank you Natalia!  That was exactly what I needed and very helpful!

You are welcome, if there is anything else that we can help with, please feel free to contact me here anytime.

DJI Natalia Posted at 10-9 20:01
Update:
Sorry for the late reply. Hope the following information can help you:
1. If you are using a Zenmuse P1 camera, you can refer to the Timestamps.MRK file generated by the camera. There are fourth, fifth and sixth lines in it, which represent the compensation value from the camera to the antenna position. You can fill in this value for PPK;

DJI Natalia you are awesome. I never would have thought that anyone from DJI would bother to answer this question, or maybe just with the traditional "sorry to hear that". Your salary must be increased by firing your useless comrades. Thanks a lot

LV_Forestry Posted at 10-10 07:40
DJI Natalia you are awesome. I never would have thought that anyone from DJI would bother to answer this question, or maybe just with the traditional "sorry to hear that". Your salary must be increased by firing your useless comrades. Thanks a lot

Much appreciated your support and feedback as well. Your positive review will be rated as a great incentive for me. Thank you very much again.

Hi DJI Natalia, i have a comment related to this topic.
The vector is defined from the GNSS antenna center to the CMOS center instead of to the projection center.
So this vector have to be corrected by perpendicular distances from the
sensor center to the projection center (by the focal length).
Is this assumption correct? Can DJI apply these corrections, or it have to be done by the adjustment software?
We work with agisoft. If an offset (focal length, i.e. 35mm) is applied in the z-direction, the result is much better.

VAHD Posted at 4-12 06:57
Hi DJI Natalia, i have a comment related to this topic.
The vector is defined from the GNSS antenna center to the CMOS center instead of to the projection center.
So this vector have to be corrected by perpendicular distances from the

Have you already estimated the error with GCPs?

Yes, it is a testfield with 44 GCPs. You can have a lok at this paper: https://www.researchgate.net/publication/360959396_INVESTIGATIONS_INTO_THE_ACCURACY_OF_THE_UAV_SYSTEM_DJI_MATRICE_300_RTK_WITH_THE_SENSORS_ZENMUSE_P1_AND_L1_IN_THE_HAMBURG_TEST_FIELD

I ran further tests with the same data from Flight 1.

VAHD Posted at 4-12 23:52
Yes, it is a testfield with 44 GCPs. You can have a lok at this paper: https://www.researchgate.net/publication/360959396_INVESTIGATIONS_INTO_THE_ACCURACY_OF_THE_UAV_SYSTEM_DJI_MATRICE_300_RTK_WITH_THE_SENSORS_ZENMUSE_P1_AND_L1_IN_THE_HAMBURG_TEST_FIELD

I ran further tests with the same data from Flight 1.

Thanks, this document is really interesting.

Do you have the opportunity to test several sensors of the same type?
I agree with your observations concerning P1 and L1, nevertheless when I compare my data with those of my colleagues who have the same sensors, for L1 everything seems stable, but for P1 there are differences. The camera calibration data embedded in the metadata seems to solve the problem with Metashape.

the document is not mine. I'm from a citiy surveyor's office. I only received the data to carry out tests with metashape myself.
I used the tutorial "DJI with RTK coordinates data processing". Do i have to consider anything else in order to use the embedded camera calibration?

VAHD Posted at 4-13 05:30
the document is not mine. I'm from a citiy surveyor's office. I only received the data to carry out tests with metashape myself.
I used the tutorial "DJI with RTK coordinates data processing". Do i have to consider anything else in order to use the embedded camera calibration?

If you mean the one below, it is not suitable for P1. Neither for L1 for its RGB photos.DJI with RTK coordinates data processing : Helpdesk Portal (freshdesk.com)

The parameters of the cameras are pre-established in the factory. They are contained in the metadata. You can go to tools-> camera calibration and there you set all the parameters. The risk in leaving them free and doing the optimization is to have a distorted raster. The altitudes in the center will be good but the further away you go, the worse they will be.





First you try it this way. Don't forget to convert the altitudes given by the drone to orthometric if necessary. DJI altitude meta data are GRS80.
If the quality of the positioning is sufficient then it's all good.

If the quality does not please you, then yes you will use the optimization but by following this tutorial:

Aerial data processing (with GCPs) - Orthomosaic&DEM generation : Helpdesk Portal (freshdesk.com)

Thank you, i will try this. But i can't find the dewarpdata in the metadata.
So the xmp-data is incompelte or the camera isn't calibrate?

<x:xmpmeta xmlns:x="adobe:ns:meta/">
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
  <rdfescription rdf:about="DJI Meta Data"
    xmlns:tiff="http://ns.adobe.com/tiff/1.0/"
    xmlns:exif="http://ns.adobe.com/exif/1.0/"
    xmlns:xmp="http://ns.adobe.com/xap/1.0/"
    xmlns:xmpMM="http://ns.adobe.com/xap/1.0/mm/"
    xmlns:dc="http://purl.org/dc/elements/1.1/"
    xmlns:crs="http://ns.adobe.com/camera-raw-settings/1.0/"
    xmlns:drone-dji="http://www.dji.com/drone-dji/1.0/"
    xmlns:GPano="http://ns.google.com/photos/1.0/panorama/"
   xmp:ModifyDate="2023-02-23 12:41:04"
   xmp:CreateDate="2023-02-23 12:41:04"
   tiff:Make="DJI"
   tiff:Model="ZenmuseP1"
   dc:format="image/jpg"
   drone-dji:Version="1.4"
   drone-dji:GpsStatus="Normal"
   drone-dji:AltitudeType="RtkAlt"
   drone-dji:GpsLatitude="+49.391306546"
   drone-dji:GpsLongitude="+8.676136211"
   drone-dji:AbsoluteAltitude="+214.636"
   drone-dji:RelativeAltitude="+60.025"
   drone-dji:GimbalRollDegree="+180.00"
   drone-dji:GimbalYawDegree="+11.20"
   drone-dji:GimbalPitchDegree="-89.90"
   drone-dji:FlightRollDegree="+2.90"
   drone-dji:FlightYawDegree="-168.90"
   drone-dji:FlightPitchDegree="-1.10"
   drone-dji:FlightXSpeed="-3.7"
   drone-dji:FlightYSpeed="-0.7"
   drone-dji:FlightZSpeed="0.0"
   drone-dji:CamReverse="0"
   drone-dji:GimbalReverse="0"
   drone-dji:SelfData=""
   drone-dji:RtkFlag="50"
   drone-dji:RtkStdLon="0.00933"
   drone-dji:RtkStdLat="0.01373"
   drone-dji:RtkStdHgt="0.02162"
   drone-dji:RtkDiffAge="1.40000"
   drone-dji:SurveyingMode="1"
   drone-dji:UTCAtExposure="2023-02-23T11:41:22.106054"
   drone-dji:ShutterType="Mechanical"
   drone-dji:ShutterCount="8"
   drone-dji:CameraSerialNumber="3XMDK7D0018583"
   drone-djiensSerialNumber="02FY414G107P"
   drone-djironeModel="Matrice 300 RTK"
   drone-djironeSerialNumber="1ZNBK3T00C005K"
   crs:Version="7.0"
   crs:HasSettings="False"
   crs:HasCrop="False"
   crs:AlreadyApplied="False">
  </rdfescription>
</rdf:RDF>
</x:xmpmeta>

VAHD Posted at 4-13 06:56
Thank you, i will try this. But i can't find the dewarpdata in the metadata.
So the xmp-data is incompelte or the camera isn't calibrate?

Yes my bad, by default P1 has "f" recorded since the lens is removable.

So you have to go perform a calibration.

You can do it with the chessboard of Metashape Tools->Camera->show chessboard, then you load the photos and you choose calibrate camera.

Or you take a flat field where you put a maximum of GCP. You align the project, you place your GCPs manually, you optimize.

For both you save the parameters and you will only have to load them and set them each time in camera calibration.

DJI Natalia Posted at 2022-10-9 20:01
Update:
Sorry for the late reply. Hope the following information can help you:
1. If you are using a Zenmuse P1 camera, you can refer to the Timestamps.MRK file generated by the camera. There are fourth, fifth and sixth lines in it, which represent the compensation value from the camera to the antenna position. You can fill in this value for PPK;

Do you have the offsets for the M30t?