What does NRTK mean?
As a reminder, the NRTK consists in sharing the data of several fixed stations in a network. They are communicated in real time to a server centre that sends users modelled corrections for the entire coverage area. There are different types of corrections in NRTK. (see our article on NRTK and RTK)
Historically, the FKP was initiated by the German-based company GEO++, the MAC by the company LEICA Geosystems and the VRS by the company TRIMBLE.
Le format FKP
In FKP format, the NRTK network will provide more corrections. Indeed, the mobile receiver will receive the raw data from the nearest station (RTK), to which we will provide precise tropospheric and ionospheric corrections. This data will allow it to converge quickly and accurately. In this case, the NRTK network needs to accurately calculate this ionosphere and troposphere information.
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MAC Format (Master Auxiliary Concept)
The MAC format consists of broadcasting the raw data from the nearest station (RTK) to the mobile receiver and adding MAC corrections to it. MAC corrections represent information from surrounding stations.
The entire NRTK network has a relatively small impact on the correction calculation, as a large part of this technology is embedded in the GNSS mobile.
VRS Format (Virtual Reference Station)
For the VRS format, the user sends his approximate position, from which the server will provide the artificial measurements that would be obtained in a very close fictional station. This will ensure very easy differential positioning. In this way, much of the work is done by the server, which will provide very accurate virtual data from models, based on actual measurements obtained on permanent stations.
In the end, whatever the type of correction chosen by the user, the accuracy remains the same and the convergence times are relatively close.
NRTK technology thus enables the TERIA network to cover all of metropolitan France, Reunion Island and Mayotte, and in 2019, French Guiana and the French West Indies.