DJI Phantom 4 Pro RTK | We Put It To The Test

Steel City Drones Flight Academy is excited to be testing and reviewing the new DJI Phantom 4 Pro RTK system at our brand new drone training facility in Fort Myers Florida. This aircraft has created quite a buzz and we’re going to put it to the test! With that said, lets dive in.

Here are a list of topics we’re going to cover in this review:

DJI CLAIMS – No Ground Control Points?

Ever since the DJI M600 first came on the scene, land surveyors and mappers alike have been asking, “Do we need to setup Ground Control Points?“, and the answer has always been, “Yes, you need ground control points with an RTK system”. That is, maybe until now…?

DJI claims the new Phantom 4 Pro RTK allows you to completely eliminate, or massively reduce ground control points and achieve up to 3 centimeters of accuracy. In much larger complex construction missions there could be a reduction from 20-40 GPC Per sq km Down to 3-5 GPC, or in some circumstances, down to zero GPC.

That is a huge claim and as a result, it has many people buying this system sight-unseen. We’re going to put this huge claim to the test, but before we test the RTK Accuracy, let’s review some of the features on the P4 Pro RTK and test overall function. (*If you can’t wait, you can always skip down to the bottom for the RTK Accuracy Test)

RTK TECHNOLOGY

As I touched on in the opener, built into the Phantom 4 Pro is this new high-precision RTK system. This is the most highest Precision RTK system that DJI has offered yet. It transfers the most data and streaming error correction from the ground control system. Additionally, the P4 RTK allows the option for PPK post-processing on your satellite data.

[PRO TIP] We receive a lot of questions about RTK technology concerning its capabilities and applications. Therefore, I want to take a moment to clarify a few things. The Phantom 4 Pro RTK will work very well around high concentrations of metal and high-voltage EMI environments. Having said that, you still need to be very careful around cell towers that use microwave dish emitters for back-haul. RTK technology cannot prevent high power back-haul that interferes with the control signal between a drone and the remote controller. mote controller.

D-RTK 2 GNSS Mobile Base Station

This is a nice piece. The base station itself is two pieces and the top piece can be easily detached without much effort. Overall, this is a good improvement over the Matrice 210 RTK system, which was a very small base station.

This could also essentially be used as a Rover. In fact, there are three three different modes that the base station can be used, but, for our testing purposes it was used as a portable station.

Tripod

When we first setup the base station, our initial impression felt this was a very well designed survey quality tripod.

One small, but nice element, to the design is the two mounted Bubble Levels. One is placed on the side and another on top. This will assist you in making sure the base station is perfectly level.

We noticed that the legs had no locking-mechanism option to keep them in place. In our opinion, it could be easily bumped which might be an issue for some people. The ability to lock it in place would had been an easy and nice option to have.

Dongle Compartment

They provide a dongle compartment mounted onto the station post that would allow you to insert a a 4G dongle inside the slot with a SIM card. This would give you the option to setup NTRIP Network to the base station, but, unfortunately, the option to setup NTRIP on the Ground station is not available at this time. DJI has not slated a date for when this will be incorporated, but we hope it will be soon. You can, however, install NTRIP on the controller.

OcuSync 2.0

The base station comes with DJI’s OcuSync 2.0 transmission system. This provides 256-bit encryption to give you better data security.  In addition, OcuSync 2 is going to give you a stronger signal quality across the board, that, in turns, allow for a longer range.

CONTROLLER

The controller is specific to the DJI Phantom 4 RTK. It comes with a micro-SD card slot,
built-in speaker, hot-swappable batteries, and Network RTK with a 4G Dongle GS RTK App pre-installed

Monitor:

Both Standard Phantom 4 Pro and the RTK version have the same built-in Crystal Sky monitor with a 5.5inch touchpad screen, 1920×1080 resolution, 4G RAM Memory+16G ROM.

Due to it being built-in, there is no other monitor options. This is a drawback for me, as I personally find this monitor to be too small; making it unnecessarily difficult to use. At a very minimum they could set it up to allow for an iPad or a have a USB out so we can actually use an external Source. I’m sure that’s going to be changed and improved with time, but right now that’s a little bit of an issue.

APPS

GS RTK APP

There is no option other than to use the GS RTK app. Some people preferred to have additional options will find this to be a negative.

Having said that, the DJI GSR app does have some nice features that allow you to create a flight plan anywhere without having to be on site. You can also save that flight plan and recall it anytime you want to fly.

Additionally, you can also import KML pre-programmed flight files. As of now, however, when our clients are trying to import the KML files into a mapping project it’s not allowing them to do so without a paid subscription to that service. That’s unfortunate and we would hope that this will change in the future.

Lastly, we ran into some issues with the app requiring numerous updates over the past month. We also ran into additional problems getting everything to connect and respond properly. The app simply has some ‘wonky’ bugs that left us thinking it could have been tested just a tad longer before going public.  Nevertheless, we’re sure that DJI is addressing these issues, hence all the updates.

TimeSync APP

One of the newest and interesting app systems in the Phantom 4 Pro RTK is DJI’s TimeSync. DJI describes it in this manner:

“TimeSync ensures each photo uses the most accurate metadata and fixes the positioning data to the center of the CMOS – optimizing the results from photogrammetric methods and letting the image achieve centimeter-level positioning data. – DJI”

This would be very appealing to surveyors and mappers alike. While drone position accuracy is important; image accuracy is just as important and TimeSync seems to address that need.

BATTERIES

The Phantom 4 Pro RTK aircraft uses the standard batteries designed for this unit. For the accessories, however, everything in this system is currently using Crystal Sky batteries. Personally, we feel it’s great to see a universal battery across the board for all the accessories.

When it comes to uniform use of batteries, this is another way it seems DJI is listening to their professional customers. This change now allows us to use the same battery on Crystal Sky monitors, ground station, remote controller, condense remotes, and so on

CAMERA

The P4 Pro RTK and Standard P4 Pro comes equipped with a 20 megapixel camera. It’s basically the same as the X4S camera and they do not offer alternative camera options at this time.

Camera Test
When we did a flight test at 200 feet, the very first thing that was noticeable is the softer resolution the camera produces. If you’re doing boundary surveys or projects that do not need higher resolution, then it’s not a big deal. If you need very crisp high-resolution image, then this might be an issue.

Camera Comparison:
Let’s take a moment to review couple pros and cons to the the P4 Pro RTK camera verses the Matrice 210 RTK with the X5S camera.

Aperture:
-The Phantom 4 Pro RTK camera has a fixed lens and cannot change the aperture. Therefore, when planning a mapping mission, you need to keep that in mind and plan the flight accordingly.
-The M210 RTK the X5S which has an adjustable aperture. You can change the lens to fit your specific application needs.

Shutter Types:
-The P4 Pro RTK camera has a mechanical shutter, which means, it opens and closes very uniform and it exposes the whole sensor at one time.
-The M210 RTK X5S has a rolling shutter. This is usually unwanted by surveyors and mappers because the shutter opening and closing creates an unwanted gap when the bottom is exposed and the top is exposed.

[PRO TIP] With the X5S camera you can definitely overcome some of the issues with the rolling shutter. If using the X5S camera you could slow your flight down, change your aperture, and make sure you get a real fast shutter speed so that opening closing time is very quick. Taking it slower will help you achieve real crisp clear picture, also you have the ability to change your GSD (ground sampling distance), which will show you how much clarity that you’ll have on the ground per Pixel.

There are some application that the Phantom 4 Pro RTK camera will do just fine and other applications that the Matrice 210 RTK system, equipped with the X5S camera, might be the best solution. It depends on your specific need and application. If you’re unsure which one is best for you, give us a call or drop us an email and we’ll help you sort it out.

WIND FLIGHT PERFORMANCE TEST

One of the first things we did when testing this aircraft was a wind test. Luckily we had some pretty significant wind for our test, up to 30 mile-an-hour wind gust. For this test, we also put a standard Phantom 4 Pro V2 side-by-side to the Phantom 4 Pro RTK to observe performance-differences.

Results:
The Standard Phantom 4 Pro dropped about 7 feet in altitude. It performed as expected which is a very typical response for a consumer-grade drone.

The Phantom 4 Pro RTK held up far better than we had expected. In fact, during the 30mph wind gusts, we didn’t see more than a 3 to 4 inch drop in altitude.
That is extremely impressive for a drone of its size and weight.

Overall, the RTK version held solid in both height and position. The wind performance alone could significantly improve survey accuracy on the z-axis.

RTK ACCURACY PERFORMANCE TEST

Now let’s get into what everyone wants to know: The Phantom 4 Pro RTK accuracy test.

Setup

Our test flight patterns were conducted at our training facility back-to-back, under the same weather conditions and flight plan..
For the mapping tests we measured 4 check points taken with Survey grade equipment strategically placed throughout the flight-plan location.

For the first part of the test, we flew the Phantom 4 Pro RTK with the RTK enabled. We also laid out 4 traditional ground control points for post processing.For the second part of the test, we flew the Phantom 4 RTK through the same flight pattern without the ground control points.

The Results | Does DJI’s claims stack up?

When evaluating any mapping data, it is very important to understand that a number of input variables entered into Pix4D can easily influence the project accuracy reports. In our opinion, the only way to verify the accuracy of the collected data, is to compare it to known reference points. Therefore, the check shots were critical to evaluating our data.

While this is not a mapping class it is also important to understand there are a wide variety of factors that can influence the accuracy of any project such as Ground Sample Distance, flight overlap, type of terrain, changes in elevation, sun angle, and much more. Therefore, the results we achieved may vary from another drone operator’s experience.

The Data:

DJI claims 3 to 5 centimeters of accuracy using NTRIP without ground control. Does it stack up? Well, we’re pleased to say that our test results were extremely accurate and produced far better results than what we would have ever expected.

No Ground Control Points
Absolute Horizontal Accuracy came in within 1.7 centimeters and Vertical Accuracy on the Z-axis came in less than 1cm. Most drones actually have a higher degree of error on the Z-axis because the aircraft’s flight path normally has more altitude variance which goes to show how tight RTK keeps the flight path. Again our results were tested against 8 different checkpoints to validate the data.

With Ground Control Points:
Adding in 4 Ground Control Points to the Pix4D project brought the overall accuracy in even tighter. Absolute Accuracy was all less than 1cm and Relative Accuracy came in, no higher than, 1.75 centimeters.

So, did DJI’s claim of accuracy hold up? Absolutely. Again, it performed much better than we anticipated and left us all feeling very impressed.

I want to point out, however, that while the Phantom 4 Pro RTK is a great tool to acquire data, it is not a replacement for traditional survey equipment or methods, in my opinion. There’s no possible way to validate data that a drone acquires without having known accurate data to double-check it against. Nevertheless, even when using ground control points, this unit would allow the ability to greatly reduce the amount of GCP needed and in turn save an enormous amount of setup time.

CONCLUSION

Our Drone testing and reviews attempt to carefully weigh out the positives and limitations of each unit so that you have a balance of information when deciding whether it’s a good match for you.

We recognize that there are growing pains with first-generation platforms and no aircraft we have ever tested has been perfect or had every option we would like. Quite frankly, everyone has different needs pending on their specific applications. Personally, we think the Phantom 4 Pro RTK has a huge Market and will become a great asset to many people.