The DJI Phantom 4 RTK might look nearly identical to the original DJI Phantom 4, but the two drones are quite different. Beyond the obvious difference — the price tag — the two drones are quite different. One, the Phantom 4 is primarily used for photographers or low-intensity enterprise projects. The second, the Phantom 4 RTK, is a powerhouse in precision mapping — a low altitude aerial sensor that claims to have centimeter-accurate data while requiring fewer ground control points.
And though the $6,500 price tag is high, it’s an incredible value for what you get.
Do I need the DJI Phantom 4 RTK?
RTK stands for “real-time kinematic,” and is used in reference to a satellite navigation technique that can enhance the precision of position data derived from satellite-based positioning systems such as GPS, GLONASS.
We’re talking centimeter-level precision.
If you’re using a drone for something like photography or search and rescue, odds are you don’t need to be ultra precise in the location of your drone. If it’s a little too far to the left, just crop your photo. Save your money and steer clear of your drone.
But if you work in the field of precision mapping, every centimeter counts. This drone will get you there, at a price point far less than what experts expected.
“The DJI Phantom 4 RTK doesn’t offer slight improvements: it’s a completely different way of working,” according to a post from drone mapping software company Pix4D (note that Pix4D does have a vested interest in the product, as images from the Phantom 4 RTK can be processed with any of the Pix4D product suite). “While RTK has been available in fixed wing drones for a while (or intrepid DIYers had the option of adding on PPK or creating a custom RTK copter) this latest release from DJI is the first quadcopter drone with RTK built in at an accessible price.”
And like all of DJI’s drones, it’s ready to use, almost right outside of the box. Aside from charging up some batteries and registering your account, you can fly the drone almost instantly upon receiving it — no soldering tools or wonky cords to deal with.
The history of drones in precision mapping
DJI launched the Phantom 4 RTK globally in October of 2018. Prior to that, drones were used in precision mapping, but it was an onerous (and expensive) process.
To achieve the precise level of data needed, operators would have to set up somewhere around 40 ground control points (GCP) per square kilometer, which could take several hours to place. (Spoiler, the DJI Phantom 4 RTK can potential reduces the number of GCPs needed to 0, which DJI says saves at least 75% in set-up time).
Just two years ago, drone mapping professional Jon Ellinger, the creator of TLT Photography, which specializes in aerial surveys and geospatial data processing outlined a very detailed guide on TheDroneGirl.com on drone spatial resolution and accuracy.
At the time, most photogrammetry software could achieve about 2-3x your GSD in relative accuracy. To achieve 2×3 your GSD in absolute accuracy (the real world location of your data), you would have needed to use a licensed surveyor with air targets or much more expensive technology and gear.
That meant either:
- Purchasing a drone platform that has very expensive RTK antennas on it that triangulate with satellites and known earth base stations
- Use a Mavic or Phantom 4 pro and use surveyed air targets (iron cross pattern works best). Then when processing, you take those surveyed points and “tie down” your table model to precisely where it should be on earth.
Companies did offer those solutions, like Skycatch, which claims its drones offer accuracy within 5 centimeters, and Kespry, whose drones have a 35mm industrial Sony APS-C Sensor. Both of those are San Francisco Bay Area based companies that offer subscription models that start at well over $1,000 per month. Denmark-based Phase One’s options run from $28,950.00 to $65,600.00
What’s different on the Phantom 4 RTK vs. Phantom 4?
With the Phantom 4 RTK, an RTK module is integrated into the drone to provide real-time, centimeter-level positioning data. The RTK module can provide positioning accuracy of 1cm+1ppm (horizontal), 1.5cm+1ppm (vertical), and the Phantom 4 RTK can get the 5cm absolute horizontal accuracy of photogrammetric models.
The drone also has a redundant GNSS module, intended to help the drone maintain flight stability in signal-poor regions such as dense cities.
The two modules are intended to optimize flight safety while ensuring precise data is captured for complex surveying, mapping and inspection workflows.
The Phantom 4 RTK’s positioning system can be connected to a D-RTK 2 Mobile Station, NTRIP (Network Transport of RTCM via Internet Protocol) using a 4G dongle or WiFi hotspot. Or you can store the satellite observation data to be used for Post Processed Kinematics (PPK).
A LinkedIn post by Northern Express Group Survey Manager Michael Cutfield tested the accuracy of the drone. He found the Phantom 4 RTK produced results with a mean RMS error of just 1.6cm in the X axis, 1.8cm on the Y axis, and 4cm on the Z axis.
Other unique features on the Phantom 4 RTK
A specific DJI Phantom 4 RTK controller
The controller is also unique to the DJI Phantom 4 RTK, namely due to a hidden USB slot which comes with a vodem stick for connecting to the internet (you supply the SIM card).
Some other differences you’ll find in the controller:
- micro-SD card slot
- built-in speaker
- hot-swappable batteries
- Network RTK with a 4G Dongle
- GS RTK App pre-installed
A feature called TimeSync enables you to continually align the flight controller, camera and RTK module, taking advantage of the positioning modules.
DJI says TimeSync enables more accurate metadata and fixes the positioning data to the center of the CMOS to help achieve centimeter-level positioning data.
The DJI Phantom 4 RTK has a 1-inch, 20 megapixel CMOS sensor, and a mechanical shutter to prevent rolling shutter blur. It can achieve a Ground Sample Distance (GSD) of 2.74 cm at 100 meters flight altitude.
A specific RTK app
While DJI Phantom 4 users are using the DJI Go App, this drone has its own GS RTK app. The app enables two planning modes – Photogrammetry and Waypoint Flight – to let pilots select the drone’s flight path while adjusting things like overlap rate, altitude, speed and camera parameters. The app also has implemented direct loading of KML area files for in-office flight planning, a new shutter priority mode to keep exposure consistent across all photos and a strong wind alarm to warn pilots of adverse conditions.
Is there SDK support for the Phantom 4 RTK?
Yes. If you intend to further develop on the software, the DJI Mobile SDK, opens up its functions to automation and customization.
How do I buy the Phantom 4 RTK?
Here’s one more area where the Phantom 4 and Phantom 4 RTK are vastly different. Whereas you can easily pick up the Phantom 4 at Best Buy or Amazon, the same can’t be said for the Phantom 4 RTK.
The easiest way to get your hands on the DJI Phantom 4 RTK is through New York-based camera store B&H Photo. The catch? They only sell the DJI Phantom 4 RTK Quadcopter with D-RTK 2 GNSS Mobile Station, which means you’re going to have to shell out more than $11,000. That’s fine if you wanted the D-RTK 2 GNSS Mobile Station anyway (that’s the price you’ll pay through any other dealer too), but if don’t need the extra mobile station, then you’re paying for more than you need — the standalone DJI Phantom 4 RTK costs $6,500. The B&H Kit is handy though as it includes the mobile station, tripod and a Nanuk hard-shell travel case, which has a $200+ value.
Otherwise, the Phantom 4 RTK and D-RTK 2 Mobile Station are available through authorized DJI Enterprise dealers worldwide. If you don’t want to work with a dealer, you can also fill out a form to purchase through DJI’s website.