PPK (post-processing kinematic) positioning is a method of correcting and improving the precision of positioning data derived from GNSS satellite constellations such as GPS, GLONASS, Galileo and BeiDou. It is typically used to provide centimetre-level precision geotagging for images captured by drones for mapping and surveying applications.
As with the related GNSS correction technology RTK (real-time kinematic), a ground base station calculates a more accurate position than a standard GNSS receiver can, by making additional measurements of the carrier wave of the received signal and using statistical and mathematical calculations to eliminate the majority of errors.
Unlike RTK, which broadcasts GNSS position corrections to drones and unmanned vehicles in real-time, the corrections are performed after the mission is finished and the corrected images have been uploaded to post-processing software either on a desktop computer or in the cloud.
PPK software applies the more accurate location information derived from the base station to the geotags captured by the drone’s onboard GNSS receiver, using timestamps to merge the two datasets.
The accurately georeferenced aerial photos can then be used to create deliverables such as digital terrain models (DTMs), digital elevation models (DEMs) and orthophoto mosaics.
The use of PPK positioning offers a number of advantages for drone mapping and surveying. Compared to traditional methods that make use of ground control points (GCPs), PPK requires far less setup time and manpower, as ground control points must be installed manually across the landscape and their position must be accurately measured.
Compared to RTK, PPK provides a more flexible approach as post-processing can be performed at any time after the flight.
PPK also does not require a constant connection to a GNSS base station, thus simplifying telemetry and increasing dependability and potential range of operation. If real-time data links are lost, a drone with autonomous functionality can still complete the survey and flights will not have to be re-run.
Due to the lack of requirement to be in range of a base station, PPK drone surveys have the potential to be performed BVLOS (beyond visual line of sight), as well as in environments that have plenty of obstacles or otherwise poor connectivity conditions.