Reach RS2 with DJI M300 and P1 Payload-PPK possibility?

Question…If you use the Emlid to measure your known point that the RTK2 will be positioned on, do you want to avoid correcting for pole height using the Reach View 3 app? I think that DJI corrects for their pole height assuming you are using the pole that comes with the RTK2. I wonder how the two interact. It seems like you would NOT use the pole height correction in Reach View 3. You would measure the height of the RTK2 and just add that pole height to the Emlid measurement.

Hi @cmsauls,

Such elevation difference usually means that you use ellipsoidal heights when you need orthometric ones (heights above geoid). For example, you collect points with Reach RS+ with ellipsoidal heights, while Agisoft uses the Global geoid by default.

If you share your ReachView 3 and Agisoft coordinate system project settings, I’ll be able to say something for sure.

UPD. Fixed the typo

Hi @contact,

If you measure a point with Reach, you receive a coordinate of the point on the ground in CSV. That’s why you need the pole height correction in ReachView 3. If you don’t use it, you’ll obtain the antenna phase center coordinates.

Thank you very much. I think you are on the right track. I’ll try to get you some information soon. In the last test, the GCPs were all very close but Agisoft was saying that some of the coordinates were off as much as 10 to 20 meters. Obviously, there are some conflicts that I have not figured out yet but I’m sure with your help we can resolve the issue. Thank you again. I’ll get you some info very soon.

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I just flew a mission today with the M300 RTK and was receiving correction. When i check my files on the SD card, I don’t have .mrk file or a .bin file… How can i get these files?

Sorry for the delay. I wanted to shoot several more test maps. I did a test measuring multiple GCP coordinates using NAD83. There were 6 different measurements in all. After looking at the CSV files it was clear that there was very little difference between all 6 GCPs, in most cases, sub-cm which included lat, long, and elevation. I feel the Emlid data is very solid. I then completed 3 maps of the same area. The first map was using the RTK2 with factory “out of the box” settings. Then I shot the next map using a custom network with NTRIP and the last map used a known point measured with the Emlid with pole height corrections. After getting the Emlid measurement I then added the RTK2 antenna height to the Emlid measurement and interred that measurement in the custom settings. When I bring all the data in Agisoft using the WGS84 all the GCPs are where they are supposed to be with acceptable errors but when I change the project settings or use the coordinate system used on the GCPs they float off hundreds of yards away or the angles of the maps change. I have tried converting the coordinates on the pictures but nothing is helping. I feel like my workflow is not right but I have tried multiple combinations and still lost. I would be happy to send you a link and share with you all the data including the pictures or I could share some specific screenshots. How do you want to handle this data? Thanks for your help.

@cmsauls,

You mentioned you processed three maps with different base settings, right? Were they all processed using GCPs?

I would like to check the screenshots of your Agisoft projects’ settings and final maps.

You’re right, it’s indeed quite hard to find the possible reasons without checking the data. I suppose it’s sensitive, so you email us at support@emlid.com.

Thank you. Yes, All maps were processed with GCPs. The three datasets were captured with the M300, P1, RTK2 and each dataset was processed using several of the RS+ CSV files. I’ll get you some information shortly.

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Dainel40, what app are you using to fly the M300? For the P4 RTK the Log files and .mrk file are only saved when you fly with DJI Pilot (android). Using GS Pro, for instance, allows you to fly RTK but it does not log the files needed for PPK.

Hi @cmsauls,

How is it going? Can’t forget your case :sweat_smile: I still think there is some coordinate systems mismatch and would like to check the data. If you sort it out, please let me know!

Yes, I haven’t forgotten. I have had some distractions in the last few weeks but I want to get this information to you this week. I just want to say that I do very much appreciate your help. You are awesome!

Thanks! :relaxed: No pressure, just worried if these difficulties affect your work.

Thanks for all the help offline. I know we have exchanged many emails working on the problem. Just wanted to give my final thoughts on the process or lack of it for anyone following this post. After trying to process in Agisoft it has been difficult to alter the WSG84 into my local coordinates. I’m still working on the problem and hopefully, I’ll figure it out. The good news is that I can process using WGS84 and the GCP coordinates collected with the RS+ with no problem. I have been testing and found that if you are careful when marking and recording the GCPs you can get cm or even sub-cm accuracy with the M300RTK and P1 camera. The big thing I learned about the RTK2 is that it is not as accurate as using the custom/advanced features in the Pilot app. I think everyone that is familiar with the DJI RTK2 system knows that. You can use the RTK2 with factory configuration or use a custom network “NTRIP” or enter the coordinates in the advanced settings. If you are truly trying to get the most accuracy I would use the coordinates of a known point and put those into the advanced settings. I collected the point with the RS+. The advanced method or custom network using NTRIP is very accurate but the advanced setting will give you the most consistency throughout the dataset. Looking at how small the error rates on all the cameras compared to the other two methods was remarkable. If I can figure out how to change the project to the local coordinates to match my GCPs I’ll let you know. Thanks again for your help.

Hi @cmsauls,

Thanks for posting this summary!

I also want to add that the coordinate system of the RTK drone’s images depends on the base/NTRIP system. For example, if NTRIP sends corrections in NAD83, images will be in the same system. It should be noted while processing them in photogrammetric software.

YES, that is good info. That is why the camera coordinates are so accurate. It may also help to try to figure out the correct workflow in Agisoft. No need to convert the camera coordinates or the GCPs if everything is captured in NAD83. The testing will continue. Thanks…

Hi there!

In case you haven’t seen this post, we’ve just released the stable version of Emlid Studio with geotagging images from RTK drones :tada: You have one, so this feature is for you!

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