Collecte de données de qualité et gestion efficace des travaux terrain

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What is post-processing

05 août 2020

There are several different methods to improve the accuracy of the positions collected with a GNSS receiver in order to achieve higher accuracy. Each method has different advantages and is better suited for different tasks and projects.

The most widely known is the Real Rime Kinematic (RTK). The data collected by one mobile receiver (rover) is corrected by a second stationary receiver (base). The stationary receiver is usually part of a network that requires a paid subscription. The connection between the two receivers requires a radio link or mobile internet connection. The great advantage of this method is that the accurate position of the rover is calculated almost immediately.
Precise Point Positioning (PPP) does not require service fees or subscriptions. It can be used in remote areas with no internet connection. Unfortunately, this method is extremely slow. In order to achieve centimeter accuracy, the receiver has to stay on the same position for many hours. The processing of the collected coordinates is delayed several weeks – the time necessary to establish the precise orbits of the satellites at the time when the data was collected.
The best of both worlds is represented by the so-called post-processing (PP) used in systems like OnPOZ Cloud. There are no service fees and one receiver is enough to obtain the best possible accuracy. Taking the position on the field can take as little as 1 second. The data is then matched to the position of a nearby public base station. In most cases, the final position can be calculated within an hour. The achieved accuracy is typically better than the RTK method.

All things considered, RTK is the most expensive way. The cost is justified by the speed when the accurate coordinates are needed right away. PPP is practical only when surveying far from the civilisation and there is no other option. Post-processing allows to collect GNSS positions quickly and precisely without costly RTK service fees. That makes post-processing the most affordable and efficient way of collecting high-accuracy positions.