The TOPODRONE PPK upgrade is a compact GNSS receiver based on a u-blox chip, integrated with the camera shutter and the drone's power system. The TOPODRONE PPK upgrade is installed at the front of the drone without blocking satellite reception of the quadcopter's main GNSS navigation module. The upgrade sits inside a plastic case matched to the drone's color, with openings for the four cameras of the forward vision positioning system.
The TOPODRONE PPK upgrade writes data to a Micro-SD memory card, which must be formatted in FAT32. Each time the receiver is switched on and initialized, the upgrade creates a folder named YY-MM-DD (year-month-day), inside which a new *.ubx file named HH-MM-SS (hours-minutes-seconds) is created. Time is recorded in UTC.
The *.ubx file logs raw GNSS measurements from the external GNSS antenna, as well as the precise moments of the drone camera's shutter release, also called timestamps or events. Each photo taken after initialization gets one timestamp. Using the *.ubx file, the original photos and the base station file, the images can be geotagged by the PPK method in TOPODRONE Post Processing.
Initialization of the TOPODRONE PPK upgrade, and thus the start of *.ubx recording, happens when the GNSS antenna sees the signal for several seconds while the drone is stationary. After initialization, the *.ubx file is recorded until the drone is powered off. Recording of the *.ubx file does not stop even if the GNSS signal is lost, for example if the powered-on drone is carried indoors. The TOPODRONE PPK upgrade cannot be initialized after the drone has already taken off.
After the drone is powered off, recording of the *.ubx file stops automatically. In normal operation, with a stable satellite signal and 20-30 minutes of operation, the *.ubx file is 20-40 MB.
Successful initialization is indicated by a blinking orange LED and a solid blue LED. If the blue LED blinks, move the drone to a more open area until the blue LED stops blinking. For details on the indicators, see section 1.3. TOPODRONE DJI MAVIC 2 PRO PPK Upgrade KIT components.
It is strongly recommended to check the initialization status before and after every flight. Recording may stop due to poor GNSS antenna contact, satellite signal interference, a full memory card or a failed memory card. If the *.ubx file or the photo timestamps are missing, further post-processing and high-precision coordinates are impossible.