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DJI Phantom 4 RTK with D-RTK 2 mobile station
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wxfloyd
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Hello everyone. I'm researching drone platforms for mapping, and my company is considering a Phantom 4 RTK, with the D-RTK 2 mobile station. I'm trying to get an important question answered, but haven't been able to so far.
If I have the D-RTK 2 mobile station, does it require a previously surveyed point for its location, in order to get RTK corrections when flying? Ideally, with my type of work, I would like to show up to a site, set up the D-RTK 2 station, begin my flight with the Phantom 4 RTK, and get RTK corrected location with the drone and ground station. If I have to survey a location for the D-RTK 2, then that would add to the complexity and time for the job. I was hoping that this setup would reduce that time so I can fly multiple sites in a short time.
I understand that I can use a wifi hotspot to connect to a correction network (assuming there's one available for the area I'm working), but some of the sites I would be working at have little to no cellular coverage.

If anyone here has any knowledge or insight on this, it would be greatly appreciated.




1-16 07:10
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MTCWBY
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The base station will find it's own lat/long wherever you put it and supply corrections to the drone. That base location is likely going to be within 4-5 feet of actual. The key is that it doesn't move because the points the drone collects are relative to it. Having a previously surveyed point with a decimal lat/long you key in can also be done and setting up over that point means that you could repeat flights that should align from survey to survey. I will caution you that the current software seems to have some issues in saying it's set but when you check you find it hasn't unless you change the Lat/long position ever so slightly. It's a bug IMO.  You don't need the wifi hotspot for flying that. The issue is that the controller won't have maps and the system complains mightily without it when you forget to turn it on. I don't know if it will actually fly in that case because I alway then turned it on to resolve the issue.
1-16 11:57
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fans89c9f498
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I've only had my system for a few days, but I see no way to locate a point to survey for the base station. There does not appear a way to store rinex for post-processing. There does seem to be a way to set it up to get network corrections, but I have not been able to get it to work. I set a point with my normal GPS unit and then set up over the point.  The resulting data was very good.
1-21 19:12
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mikesobola
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MTCWBY Posted at 1-16 11:57
The base station will find it's own lat/long wherever you put it and supply corrections to the drone. That base location is likely going to be within 4-5 feet of actual. The key is that it doesn't move because the points the drone collects are relative to it. Having a previously surveyed point with a decimal lat/long you key in can also be done and setting up over that point means that you could repeat flights that should align from survey to survey. I will caution you that the current software seems to have some issues in saying it's set but when you check you find it hasn't unless you change the Lat/long position ever so slightly. It's a bug IMO.  You don't need the wifi hotspot for flying that. The issue is that the controller won't have maps and the system complains mightily without it when you forget to turn it on. I don't know if it will actually fly in that case because I alway then turned it on to resolve the issue.

So, for cm-level accuracy, I have to set up over a GCP?  Also, I have not found a way to input Lat/Long into the base station in the case that I were to set up over a known point.  Where do I find this info?  Didn't see it with the reams of info in the manual.

M
1-23 20:14
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mikesobola
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Also, I didn't pay $8k to have to pay for and subscribe to a correction network as well.
1-23 20:15
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DroneRunnerPlus
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I do not have mine yet, but according to the manual you can manually enter the  coordinates of your known control point. Be aware that you will have to do this or continue to set at least 3 GCPs to locate the survey in relation to your ground coordinates. For real accuracy you should turn off RTK and post-process. Just because you have an RTK fix does not mean you are getting precise data. You will need the equivalent base OBS, rover (drone) OBS and satellite NAV file which I believe is in PPKRAW. I use RTKLIB and Geosetter to post-process and update the geotags with my PPK drone. DJI should not have used the term RTK.
1-26 06:43
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DroneRunnerPlus
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Other forums are discussing the same issues.

https://forum.dronedeploy.com/t/ ... pk-processing/12201
1-26 06:57
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MTCWBY
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DroneRunnerPlus Posted at 1-26 06:43
I do not have mine yet, but according to the manual you can manually enter the  coordinates of your known control point. Be aware that you will have to do this or continue to set at least 3 GCPs to locate the survey in relation to your ground coordinates. For real accuracy you should turn off RTK and post-process. Just because you have an RTK fix does not mean you are getting precise data. You will need the equivalent base OBS, rover (drone) OBS and satellite NAV file which I believe is in PPKRAW. I use RTKLIB and Geosetter to post-process and update the geotags with my PPK drone. DJI should not have used the term RTK.

I'm not finding that to be the case. Flying using RTK is resulting in more accurately positioned pictures from the UAV and then is tagging them with the higher accuracy. The resulting models are very internally consistent and I'm seeing better results than I saw with PPK processed photos.  YMMV
1-29 09:30
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MTCWBY
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mikesobola@veri Posted at 1-23 20:14
So, for cm-level accuracy, I have to set up over a GCP?  Also, I have not found a way to input Lat/Long into the base station in the case that I were to set up over a known point.  Where do I find this info?  Didn't see it with the reams of info in the manual.

M

No, the data appears to be internally consistent with itself. Using the base without locating over a GCP with known lat-long means it's likely shifted by whatever amount the base lat-long is shifted. There are ways to shift it back and if you're using an arbitrary job coordinate system you'll have to do it anyway.  
1-29 09:34
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CHASCOADMIN
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MTCWBY Posted at 1-29 09:30
I'm not finding that to be the case. Flying using RTK is resulting in more accurately positioned pictures from the UAV and then is tagging them with the higher accuracy. The resulting models are very internally consistent and I'm seeing better results than I saw with PPK processed photos.  YMMV

The point I am trying to make is that the P4R will be all that some people will need, but if you are trying to get survey-grade accuracy then you should use PPK and 3 GCP's. This is recommended by DJI also. Beyond that what happens when you lose your RTK connection? Unless you are always surveying in clear view and flat terrain - which we don't. If you have done enough RTK surveying and have analyzed the data RTK doesn't always mean good data. Especially when you are hopping on and off.
1-29 09:49
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CHASCOADMIN
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MTCWBY Posted at 1-29 09:34
No, the data appears to be internally consistent with itself. Using the base without locating over a GCP with known lat-long means it's likely shifted by whatever amount the base lat-long is shifted. There are ways to shift it back and if you're using an arbitrary job coordinate system you'll have to do it anyway.

Shift and scale factors is something that many people are going to learn the hard way. If you think you are going to take a P4R, fly and give the customer something besides a map then you better hope that they can deal with all the data. I'm the VDC Manager for a General Contractor and we have in-house Surveyors, CAD Technicians, GPS Technicians and UAV Services. I see other people trying to do what we are doing and feel their pain.
1-29 09:52
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MTCWBY
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CHASCOADMIN Posted at 1-29 09:52
Shift and scale factors is something that many people are going to learn the hard way. If you think you are going to take a P4R, fly and give the customer something besides a map then you better hope that they can deal with all the data. I'm the VDC Manager for a General Contractor and we have in-house Surveyors, CAD Technicians, GPS Technicians and UAV Services. I see other people trying to do what we are doing and feel their pain.

We write software to do the data reduction, deal with scaling, etc. In fact I believe your company is one of our customers.
1-29 14:25
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MTCWBY
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CHASCOADMIN Posted at 1-29 09:49
The point I am trying to make is that the P4R will be all that some people will need, but if you are trying to get survey-grade accuracy then you should use PPK and 3 GCP's. This is recommended by DJI also. Beyond that what happens when you lose your RTK connection? Unless you are always surveying in clear view and flat terrain - which we don't. If you have done enough RTK surveying and have analyzed the data RTK doesn't always mean good data. Especially when you are hopping on and off.

I use GCP's as checkpoints but haven't found them to improve the result. In fact if anything they seem to warp the results to some degree depending on the processing software. And not to the betterment of the results. There are variables and if you lose corrections certainly there will be issues. That said, I haven't had problems on the five sites I've flown since just before Christmas. Being several hundred feet in the air means that trees, etc. are not a problem.  
1-29 14:33
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CHASCOADMIN
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MTCWBY Posted at 1-29 14:25
We write software to do the data reduction, deal with scaling, etc. In fact I believe your company is one of our customers.

I guess since I have no way of knowing who you are it is possible, but highly improbable. The shifts and scale factors that I'm talking about noone is helping us with and I am one of the few that has been able to do it out of all of the companies that I know that are using drones.
1-29 15:01
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CHASCOADMIN
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MTCWBY Posted at 1-29 14:33
I use GCP's as checkpoints but haven't found them to improve the result. In fact if anything they seem to warp the results to some degree depending on the processing software. And not to the betterment of the results. There are variables and if you lose corrections certainly there will be issues. That said, I haven't had problems on the five sites I've flown since just before Christmas. Being several hundred feet in the air means that trees, etc. are not a problem.
That is really good to hear. I've heard more bad stories about losing rtk connection or corrupted data than I have good ones so your story gives me a little bit more confidence. As far as gcps though, if you're not getting better results then something is wrong. I just went through a 5 stage test that proves that PPK with gcps is  superior to other methods.
Have you ever ground-truthed and staked out your drone surface?
1-29 15:05
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MTCWBY
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CHASCOADMIN Posted at 1-29 15:05
That is really good to hear. I've heard more bad stories about losing rtk connection or corrupted data than I have good ones so your story gives me a little bit more confidence. As far as gcps though, if you're not getting better results then something is wrong. I just went through a 5 stage test that proves that PPK with gcps is  superior to other methods.
Have you ever ground-truthed and staked out your drone surface?

It's part of research we're doing. We are always topoing areas with RTK when we fly to validate the drone results because this drone is so new that there isn't a lot of info out there. My background is actually total station and then RTK software going way back so we're using a lot of those tools as part of the validation.  And typically what I'm doing is processing the same flight capture with no GCP, with GCPs, and as Checkpoints to try and isolate the variables and in several different processing packages. I can't talk about whose processing software is doing better than others but there does seem to be some difference. I've been really pleased with some of the results and not so pleased with others but the drone despite some DJI bugs is impressive. There are rough edges in the software that have bitten us but once found we've worked around them. I will always recommend GCPs at this point but the number required is diminished by quite a bit. That said, I'm trying to fly as much as possible to figure out the envelope and what we can recommend.
1-29 15:27
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CHASCOADMIN
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Very, very nice. I only know a few people that are taking it to this level and I don’t know how you would be confident in providing drone data beyond maps without it. We should start another thread for processing and another for point cloud editing. The poor P4P channel is going to get flooded with mappers! Hopefully they will at least break out the P4RTK.
1-29 15:58
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MTCWBY
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CHASCOADMIN Posted at 1-29 15:58
Very, very nice. I only know a few people that are taking it to this level and I don’t know how you would be confident in providing drone data beyond maps without it. We should start another thread for processing and another for point cloud editing. The poor P4P channel is going to get flooded with mappers! Hopefully they will at least break out the P4RTK.

It's brand new and wide open from what I can tell. New stuff popping up every day
1-29 18:14
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wxfloyd
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CHASCOADMIN Posted at 1-29 09:49
The point I am trying to make is that the P4R will be all that some people will need, but if you are trying to get survey-grade accuracy then you should use PPK and 3 GCP's. This is recommended by DJI also. Beyond that what happens when you lose your RTK connection? Unless you are always surveying in clear view and flat terrain - which we don't. If you have done enough RTK surveying and have analyzed the data RTK doesn't always mean good data. Especially when you are hopping on and off.

PPK is the direction I'm starting to look towards over RTK.  The type of jobs we do require traveling across the country (U.S.), and the possibility of RTK corrections dropping midflight worries me a bit.  Especially since I wouldn't really know until returning to the office and looking at the data.  
One PPK option I'm looking at is the Propeller PPK Package, using a Phantom 4 RTK (drone only) and Propeller Aeropoints.  It gives me the simplicity of arriving at a site, dropping the Aeropoints, flying mission, then post processing at the office.   
1-30 06:10
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MTCWBY
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wxfloyd Posted at 1-30 06:10
PPK is the direction I'm starting to look towards over RTK.  The type of jobs we do require traveling across the country (U.S.), and the possibility of RTK corrections dropping midflight worries me a bit.  Especially since I wouldn't really know until returning to the office and looking at the data.  
One PPK option I'm looking at is the Propeller PPK Package, using a Phantom 4 RTK (drone only) and Propeller Aeropoints.  It gives me the simplicity of arriving at a site, dropping the Aeropoints, flying mission, then post processing at the office.

It depends on the site but so far dropping corrections has not been an issue. The worst case is the drone on the ground because once it's in the air the obstructions for it have to be mountain sized. I have not had any problem getting corrections and RTK GPS far better than it was ten years ago for both satellite coverage and the receivers themselves. My WAG is that if you can get RTK on the ground, you'll be able to get it in the air.

As for knowing whether you have corrections or not on photos, at the end of the flight the software gives you a breakdown of position qualities for the flight so you have some idea right there. I still preview mine onsite with a laptop just to make sure I have the coverage needed. That's a bigger concern IMO if there's much complexity.
1-30 10:04
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fans9e1f2813
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mikesobola@veri Posted at 1-23 20:14
So, for cm-level accuracy, I have to set up over a GCP?  Also, I have not found a way to input Lat/Long into the base station in the case that I were to set up over a known point.  Where do I find this info?  Didn't see it with the reams of info in the manual.

M

As far as i have it- you can manipulate the inputs of location on the controller RTK option advanced settings. Any other advice from somebody else. If you have a good base station signal, you will ha e within 2cm accuracy. Why do you want to be more accurate? For absolute accuracy the GCP’s will need to be surveyed with a GPS locator handheld device, like a Trimble GPS device. Those GCP’s location detail are then input into the third party software like Pix4D.
5-11 00:46
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DJI4Survey
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In order to get the D-RTK base station to be accurate, you need to have a reference station (GCP) to set the unit over and then enter these coordinates in the GNSS Coordinate Input panel.  The lat/long and altitude that the D-RTK generates when it powers on is as accurate as it can be, but you will still find large variances compared to the local coordinate system, especially in height.

This means that you will generally need a known permanent survey mark to set up on, or have another GPS (Trimble etc) to place the GCP that is receiving corrections from a known base station.

If you are doing work in a lot of areas, a network correction license is going to be the best way to get the P4RTK to work to survey grade accuracy.

Also, just be aware if you are doing jobs as a business most clients will specify what coordinate system they want the data delivered in.  As all DJI data is captured in WGS84 and Ellipsoidal height, you will need to have some software that will allow you do the datum conversions accurately.

Hope that helps.

Cheers,
5-12 13:29
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Christoph S
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MTCWBY Posted at 1-29 09:30
I'm not finding that to be the case. Flying using RTK is resulting in more accurately positioned pictures from the UAV and then is tagging them with the higher accuracy. The resulting models are very internally consistent and I'm seeing better results than I saw with PPK processed photos.  YMMV

Any experiences or recommendations which rtk provider I should use, I am in Germany.
6-16 10:44
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MTCWBY
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Christoph S Posted at 6-16 10:44
Any experiences or recommendations which rtk provider I should use, I am in Germany.

Look to see if you have a SmartNet system. They are part of Leica Geosystems and based in Switzerland. I'm not familiar with the options in Germany past that unfortunately.
6-20 08:14
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Dario M Afonso
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Good afternoon, I am trying to generate a flight plan with a Phantom 4 RTK, (the remote control has an integrated screen), the problem is that when I want to mark the route on the map, this map is outdated so I can not see the current terrain.
Does anyone know how to update this map? it's Mapbox
Thanks
6-27 14:32
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DJI4Survey
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Hey mate,

No support for adding updated imagery into the Phantom 4 RTK at this stage.  You are stuck with what Mapbox gives you in that area.

The best option is to generate a boundary KML of the area you want in google earth or other software package (GlobalMapper, ArcGiS etc).

This KML can then be imported onto the controller via the MicroSD card

You have to create a folder called DJI, and a subfolder called KML.

Place the KML in there, insert the SD card and you should be prompted to import the KML onto the controller.

Once it is on there, you can use the KML to plan your flight quite easily.

Cheers,
Tim.
6-27 17:33
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Dario M Afonso
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DJI4Survey Posted at 6-27 17:33
Hey mate,

No support for adding updated imagery into the Phantom 4 RTK at this stage.  You are stuck with what Mapbox gives you in that area.

Excellent friend, thank you very much for your response. With this I have solved the problem. And let's hope that Mapbox is resolved soon. Greetings and again many thanks.
6-28 03:50
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steffnat
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Christoph S Posted at 6-16 10:44
Any experiences or recommendations which rtk provider I should use, I am in Germany.

Hallo Christoph,
as far as I know basically all Correction Providers (Leica - SmartNet, Axio/FarmNET, Trimble - VRS Now) are using (among eventually own stations) the station network of the SAPOS services run by the Federal Land Surveying Offices of Germany.
More and more German Federal States are offering these services (HEPS - Hochgenauer Echtzeitpositionierungsdienst) for free - especially for agriculture and forestry use.
Some offer the EPS (Echtzeitpositionierungsdienst) service for free (Baden-Würtemberg) with ca. 30 cm resolution.
So I would recommend to have a look here - https://www.sapos.de/

Best regards!
Steffen
6-28 03:55
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Trey Swann
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We've been struggling with the DJI base station since October of 2018. We found that the DJI base station paired with the Phantom 4 RTK is capable of calculating image geolocation with high precision, but low accuracy. So we have been using our Trimble base station and a PPK processing workflow, that has worked really well. But, we have been wanting to utilize the DJI base station in order to realize the full potential of this system.

Aerotas just put out a workflow that seems to work. Aerotas has developed a combined field/office workflow that enables surveyors to lock the relative accuracies in photogrammetry processing and shift the entire project to match a single ground control point.

This allows surveyors to ensure full-site accuracy without the need for manual PPK processing, or ground control distributed throughout the entire project site.

DATA COLLECTION WORKFLOW
-Mission Planning
-Set & Measure Ground Control / Checkpoints
-Turn on / setup drone equipment
-Fly Site
-Considerations for large multi-battery missions

OFFICE PROCESSING WORKFLOW
-Process Sparse Point Cloud
-Adjust to align with GCPs
-Run quality assurance checks
-Process full-resolution outputs
-Draft Linework, and Integrate into CAD

See: www [dot] aerotas [dot] com / dji-d-rtk-2-survey-workflow

8-1 11:44
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Hurricane323
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Why are PPKRAW.BIN files showing 0KB?
10-17 21:21
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Vikas Vishwa
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Hi need help in using D RTK 2 handheld mode . means mose 3 .
11-5 05:26
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djiuser_ZVnri8WvpQgB
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Vikas Vishwa Posted at 11-5 05:26
Hi need help in using D RTK 2 handheld mode . means mose 3 .

I purchased a second D-RTK 2 station and am running them together.  The accuracy is pretty good, it creates a FIX connection with 0.5-1.0cm accuracy.

We wanted to use the system more in a dense forest without possibility, but when used out in the open area the connection was surprisingly not bad, I could walk for about 600m or so before it would tell me the RTK signal was weak, but if there was any kind of interference (trees, hills, etc.) then the signal was low or completely lost.  If you purchase/buy into a NTRIP account, and use an Android device as others have spoken about in other posts to link the Wifi/RC to the unit to connect to the account and get the connection data.  But for the purchase I've been happy and in the end I feel it will be more cost effective than a "professional survey rover" and all the post processing fees that go along with those types of purchases.  Very reliable they are, but also very expensive for a start-up, so far I've been somewhat impressed with the system, but battery swaps during photogrammetry flights are another issue....
11-5 12:44
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