General RTK / PPK Processing

Why use RTK / PPK

RTK (Real Time Kinematic) and PPK (Post Processed Kinematic) are two very similar processes for using detailed satellite observations to document highly accurate locations for the aircraft and sensor location during drone photogrammetry or lidar.  Typically, this requires a specialized GPS antenna and receiver on the aircraft itself to receive, store, and compute dual-band satellite data. 

RTK and PPK processing can increase the accuracy of a final project, while reducing the number of ground control points required, because the location of the aircraft, and subsequently its camera, is known to a high degree of confidence.  Typically, the most significant benefit of using onboard RTK or PPK is the reduction of required ground control points to achieve a certain level of accuracy.

Accuracy & RTK/PPK

When using on-board RTK/PPK, it is still necessary to perform some measurements on the ground. While a great deal of marketing material published by hardware manufacturers claims that RTK/PPK can provide accuracy without ground data, this does not meet minimum surveying standards or ASPRS positional accuracy standards.  At the very least, it is strongly recommended to set a handful of independent checkpoints to verify the accuracy of the project data prior to sealing any survey based on airborne RTK data. 

RTK vs PPK difference

RTK and PPK operate on the same basic principles of using GPS signal phase differentials between a base station and a rover to calculate extremely precise location information.  The difference between them is that RTK is processed in real-time in the field, while PPK is post-processed in the office. 

Real-time processing offers the benefit of quicker access to location data. It requires a radio or internet-based link from the aircraft to its base station or network of base stations. Fortunately, most worthwhile modern-day RTK-enabled survey drones implement RTK processing automatically, simplifying the field workflow. Because of this, Aerotas always recommends flying with RTK enabled if possible, which in most cases, is enough to get high-quality survey data.

PPK offers a bit more exacting control over the data. With PPK you need to do all of the calculations of an RTK system, in the office after the data has been collected. This method offers a lot of visibility into the data you’re working with. However, it also requires specific knowledge, tools, and workflows to perform the processing efficiently and accurately.

Both RTK and PPK require in-office processing to ensure proper photo and/or lidar point cloud georeferencing. Because of this, Aerotas uses a blended RTK/PPK workflow when CORS or third-party base station data is available.

To add an extra layer of assurance to your next RTK drone survey, consider running a third-party base station on-site for the entire duration of your flight. This methodology allows for the highest degree of accuracy possible on each project when nearby CORS stations are unavailable.