FKP / MAC / VRS, what are their specificities?
FKP / MAC / VRS are correction formats in NRTK. This one shares the data of several fixed stations of a network (See our article).
Each format has its own particularities, we will see together which ones.
In FKP, the NRTK network will provide more corrections. As with the MAC format, the mobile receiver will receive raw data from the nearest station (RTK), to which we will provide accurate tropospheric and ionospheric corrections. This data will allow it to converge quickly and accurately. In this case, the NRTK network needs to calculate this ionosphere and troposphere information accurately.
MAC Format (Master Auxiliary Concept)
MAC is the format used to broadcast the raw data from the nearest station (RTK) to the mobile receiver and add specific corrections (MAC) to it. It will therefore provide information from the surrounding stations. This allows the mobile receiver to calculate its own local NRTK corrections.
The entire NRTK network has a relatively small impact on the calculation of corrections. The reason is a large part of this technology is embedded in the GNSS mobile.
VRS Format (Virtual Reference Station)
For the VRSformat, the user sends his approximate position, from which the server will provide the artificial measurements that would be obtained in a very close virtual station. This will allow for very easy differential positioning. In this way, much of the work is done by the server. It 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. 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.