A GPS receiver to be "precise" needs to receive "corrections" in real time.
In the second video, at minute 1.18, we see that the pilot can choose between 2 options:
1) RTK base station
2) Custom network RTK
In the first case it is necessary to "link" the drone to the mobile station.
In the second case I believe that the corrections are transmitted via internet services or even in postprocessing phase at home.
I think this drone can reach centimetric precisions even without the mobile station and without control points.
I hope the field tests will be released in the next weeks...
Reporting from DJI site:
A new RTK module is integrated directly into the Phantom 4 RTK, providing real-time, centimeter-level positioning data for improved absolute accuracy on image metadata. Sitting just beneath the RTK receiver is a redundant GNSS module, installed to maintain flight stability in signal-poor regions such as dense cities. Combining both modules, the Phantom 4 RTK is able to optimize flight safety while ensuring the most precise data is captured for complex surveying, mapping and inspection workflows.
Fit the Phantom 4 RTK to any workflow, with the ability to connect this positioning system to the D-RTK 2 Mobile Station, NTRIP (Network Transport of RTCM via Internet Protocol) using a 4G dongle or WiFi hotspot, or store the satellite observation data to be used for Post Processed Kinematics (PPK).