Comparison between PPK and RTK Correction Systems

One of the questions that topographers often ask themselves when buying drones for topography is whether to choose one with RTK (Real Time Kinematic) technology or one with PPK (Post Processed Kinematic) technology. Especially when comparing price, usage and long-term investment. After all, an RTK drone is a bit more expensive than a PPK survey drone. In this post we will make a comparison between RTK vs PPK so you can choose which one fits your needs.

What is RTK and PPK?

Both are GNSS correction technologies that facilitate the taking of geo-referenced aerial photographs.  Below we will see the definition of each of them: 

RTK 

This type of measurement occurs when we have a GNSS base that connects directly to the GNSS rover and sends corrections via radio signal. In this way, both the base and the rover receive signals from the same satellites and through this direct radio link the corrections are transmitted in real time, achieving a high accuracy in the same field of data capture. 

Although RTK is a fairly efficient correction technology, it has a disadvantage: if an obstacle interrupts the radio data transmission, the measurement error margin may be adversely affected.

PPK

PPK is an alternative technique to RTK, in which positioning corrections are applied retrospectively. This means that, in PPK mode, it is not necessary to have a connection between the GNSS rover and the GNSS base station while working. You only need to record raw GNSS data (logs), which are then processed to receive accurate positioning data and used for calculations in post-processing.

The technique is widely used for drone mapping and for high-precision topography data collection. PPK can also be used as RTK backup for any topography work.

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RTK VS PPK: DIFFERENCES

In summary, with RTK we have a base with a direct link to a rover, while in PPK this direct link does not exist, since the data has to be processed afterwards. In that sense, there is no real time information in PPK which eliminates the risk of data loss during transmission and radio connection.  

IN RTK:

• Complete correction immediately after flight.
• Provides highly accurate, real-time position of the drone.
• Eliminates or limits the number of ground control points, if all connections are constant throughout a survey.
• Ideal for geotagging with absolute accuracy throughout real-time flights.
• No need for GNSS post-processing with real-time correction.

IN PPK:

• Using PPK for drone mapping reduces the amount of ground control points needed. This saves a lot of preparation time in the field and allows you to work in much larger and more difficult areas.
• PPK provides a more reliable and simpler workflow, because you don’t need to think about the constantly stable connection between rover and base. This makes it ideal for flights over larger areas.
• Your GNSS base station does not need to be connected to a drone ground station.
• PPK also allows longer ranges: for example, our X5 multi-band GNSS receiver can operate over distances up to 60 km in RTK, but well over 100 km in PPK.
• Processing can be run multiple times with different configurations.
• What does it depend on to choose one technology or another?
• It really depends on your specific mission, including the connections available in the local working area. Either way, RTK and PPK each have different advantages, which can help make your decision the right one.

As for the type of drone equipped with PPK or RTK systems, to make the right choice you should consider: 

• The type of drone: flight time, communication systems, payload capacity. 
• The atmospheric conditions of operation. 
• Pilot’s skills. 
• Technical specifications of GNSS systems. 
• The type of software to be used later.

After knowing the differences between PPK and RTK, we invite you to get the equipment you need for your project or business at Mettatec.