The commercial drone industry has grown extensively since the launch of the Phantom 4 Pro in 2016. Drones are now commonplace in a range of industries from search and rescue to mining and utilities. But it is the mapping and surveying industry which has taken up drones more than any other sector.
Drones provide significant efficiency and safety enhancements over existing mapping methods which have led to surveyors quickly adopting the devices to create 3D point clouds. Despite this, DJI has never made a drone specifically for the mapping and surveying industries.
Up until now, many operators opted to use the Phantom 4 Pro. While this is a very capable drone, the fact remains that it was designed to be a general purpose drone, not one specifically designed for mapping or surveying. As a result, the Phantom 4 Pro can’t deliver the accuracy that surveyors and cartographers demand without extensive use of ground control points.
To solve the problem, DJI announced the new DJI Phantom 4 RTK drone and D-RTK 2 mobile station at Intergeo 2018 in Frankfurt, Germany. The RTK has been developed specifically for surveying and mapping applications and comes with a range of features which should make it the de facto choice for the industry.
So let’s take a closer look at the technical features of this new drone to see how it improves on the Phantom 4 Pro for surveyors and cartographers.
While it may look similar on the outside, the Phantom 4 Pro RTK has been redesigned from the ground up to achieve survey-grade absolute accuracy by reducing ground control points. The drone uses a state of the art RTK module fitted directly on top of the frame to provide real-time positioning data.
RTK (Real-Time Kinematic) is a satellite navigation technique which is used to enhance the precision of data obtained from popular Global Navigation Satellite Systems (GNSS) including BeiDou, Galileo, GLONASS and Global Positioning System (GPS).
The Phantom 4 Pro may require up to 15 ground control points (GCP) per square kilometre to create accurate maps. But with its high-performance imaging system combined with RTK data, the Phantom 4 RTK requires minimal GCPs to be placed for redundancy or as a check to confirm accuracy. This dramatically reduces setup time while improving image accuracy.
One of the biggest changes in the Phantom 4 RTK over the Pro is the introduction of the DJI D-RTK flight control system. This advanced computer vision system uses dynamic differential technology to provide highly accurate 3D positioning. The system is much more efficient and accurate than the barometer, compass and GPS system fitted as standard on the Phantom 4 Pro.
Real-time accurate data transmission with TimeSync
Collecting all this extra information requires a rethink of how the data is transmitted real-time from the drone to the ground controller or mobile device. This led DJI to create TimeSync which continually aligns the flight controller, camera and RTK module during the flight to ensure accurate image data is collected.
In addition, TimeSync fixes the positioning data to the centre of the CMOS sensor which ensures each image contains the most accurate metadata. This optimises photogrammetry and helps give the Phantom 4 RTK its centimetre-level positioning data which is crucial for creating accurate 3D point maps.
More precise imaging technology
One criticism of the Phantom 4 Pro was its lack of ability to take 4k videos of a moving subject. Such images would often result in rolling shutter blur which was due to the limitations of the electronic shutter used for video capture. The Phantom 4 RTK solves this problem by using a mechanical shutter for both stills and video capture.
The ground sampling distance has also been improved. The 1 inch, 20 megapixel CMOS sensing system in the Phantom 4 RTK can achieve a Ground Sample Distance (GSD) of 2.74cm at 100m altitude. That’s an 8% improvement on the Phantom 4 Pro, which has a GSD of 2.95cm at the same altitude. This allows operators to fly at a higher altitude, reducing image counts and decreasing processing time.
Purpose-built flight planning application
The Phantom 4 RTK introduces two new planning modes for operators to make the best use of the new technology. Photogrammetry and Waypoint Flight modes are available alongside traditional flight modes such as Sport mode. These new modes allow the pilot to plan flight paths directly on the flight controller or via the DJI Go App using waypoints. They also give the pilot access to flight parameters such as airspeed, altitude and overlap rate.
There are a number of benefits to this new system but one of the most useful is that it allows the operator to create automated workflows allowing flights to be repeated to collect the same data across different periods. This feature is specifically targeted at the surveying industry who have a need to monitor site progress over a period of months.
Finally, a welcome addition to the flight planning application is the ability to carry out in-office flight planning by enabling direct loading of KML and KMZ files. That allows operators or surveyors to spend more productive time in the office and less time on-site.
Safer, smarter and more stable
The Phantom 4 RTK introduces a range of features aimed at creating a safer, smarter and more stable flying experience. The drone comes with DJI’s OcuSync video transmission system as standard. This creates a stable connection with strong interference resistance between the drone and remote controller using 2.4 GHz/5.8 GHz dual-frequency transmission.
OcuSync also allows 1080p video transmission feeds at a distance up to 7 km. This is an improvement on the Lightbridge 2 system fitted to the Phantom 4 Pro, which only allows for 720p video transmission over the same distance. When combined with the improved interference resistance of OcuSync, this makes the Phantom 4 RTK the smart choice for surveying large tracts of land in built-up areas.
DJI also reports that the battery life has been improved albeit slightly. The new drone offers a flight time of around 30 minutes, which is a slight improvement over the 28-minute flight time of the Phantom 4 Pro. One welcome improvement, however, is the RTKs ability to automatically resume a mission after the battery has been replaced.
Compatible with D-RTK 2 Mobile Station
Finally, the new drone is compatible with the DJI D-RTK 2 Mobile Station which provides real-time differential data. When combined with the OcuSync transmission system this creates a highly accurate mobile surveying solution capable of obtaining centimetre-level accurate data even in the most challenging conditions.
All things considered, the Phantom 4 RTK is a vast improvement over the Phantom 4 Pro for surveying and cartography applications. It’s obvious that DJI has taken advice from the industry on how to improve the drone to simplify operational steps and improve workflows.
If you would like a demonstration of the new Phantom 4 RTK, get in touch with the drone experts at COPTRZ. We’ll be happy to show you the capabilities of this new drone and how it can be used to streamline workflows and increase the productivity of your surveying tasks.
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