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

I have some questions Elena. I’m using the the M300 with the RTK2 and the RS+ to record my GCPs. I have used the RS+ with NTRIP to record a known point. I use this point and input the coordinates in the advanced RTK settings of the Pilot app. When finished mapping I have 4 files on the SD card in the P1 camera. They are Timestamp.MRK, PPKRAW.bin, PPKOBS.obs, and PPKNAV.nav. I’m having trouble trying to use the workflow in REDcatch. I’m working with them now and they seem very helpful. We are sending them a dataset with all my RS+ GCP information and they are going to look at it. Do I need to be logging anything in the RS+ while I’m flying. I guess I’m missing something.

Hi @cmsauls,

Do you have issues with GCPs from Reach RS+?

I haven’t had a chance to work with REDcatch software. So, I’m not an expert here. But in general, if you use Reach RS+ for GCPs, you don’t need anything but CSV with points coordinates.

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Yes and NO. I can use the RS+ to get cm and sometimes sub cm readings. I have no issue exporting the CSV file and importing them into the Agisoft software. The only thing that I am having issues with is that the GCP locations are sometimes 10 to 15 meters above ground or at least above the map. The lat and long positions are 99%+ accurate. After doing a test several days ago I did get the GCPs to show about 99% accurate elevations although I’m not sure what I did to achieve this. I was using the same system and settings as a map several days before but with a completely different outcome. I know that the RTK2 records coordinates in WSG84. My NTRIP service provider uses NAD83(2011). There are several vertical datum options that I can use and have tried all of them. I guess there is some setting in Agisoft that I haven’t found yet but I have tried several relating to the coordinate systems including the one in Agisoft where you can use the coordinate system that you used for the GCPs. I think my biggest question is how the two coordinate systems interact with each other and IF they are not syncing with each other then which one do I believe? Is the map too low or are the GCPs too high? The software you can manually adjust the GCP coordinates but that doesn’t seem right. ALSO, I sent a small dataset to REdcatch and I was asked to also send the base station data. All I have is the files that the P1 records and the CVS file from the RS+ for the GCPs. Not sure what he wants. Thanks for your reply.

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The guys at REDcatch advised that I don’t need their software workflow using the RTK2 BUT they suggested using the RS+ to get better more accurate coordinates and insert those into the RTK2 advanced settings. I just have to figure out why my GCPs are off. I’ll continue to work on it.

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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