A Hybrid solution PPP-RTK, a major asset for the CORS Network

PPP-RTK is an hybrid positioning technique of Network RTK (Real Time Kinematic) and PPP (Precise Point Positioning). These two techniques allow to calculate the position of a user using GNSS data: each of these techniques has a real interest in the resolution and the determination of the position with a global approach. RTK method uses a Continously Operating Reference Stations (CORS) network to collect data. The hybrid solution PPP-RTK uses precise data as in PPP but accelerates its resolution by using data from the CORS network as in RTK, in particular to speed up the resolution of ambiguities. This solution is divided into three parts: the network part with the collection of different data, the user part which calculates its position and finally the corrections part which is the message that sends the data to the user to calculate its position. NRTK and PPP-RTK use the data of the CORS network for the position's calculation. The density of the network is generally around 50km between two stations. The density of the CORS network can be a criterion of performance between the wellknown technique Network RTK and PPP-RTK. The objective is to compare the accuracy of the PPP-RTK solution with the position calculated in NRTK in the same area. The set up of the comparison between both techniques used firstly, the all CORS of one region of the french Teria network. The choosen region has 14 CORS and each station is about 70 km away from each other. In this first study, both NRTK and PPP-RTK achieve centimeter accuracy in few seconds. Then, in a second time, the density of the CORS network is reduced: 140km between two CORS on average. The goal is to make the CORS network even less dense to see how the accuracy is modified by using less data for both NRTK and PPP-RTK. At the end, the position will be more accurate with the PPP-RTK technique in the second case thanks to the more global approach of the solution and the parameters. Also, this implementation would provide insight into the impact of ambiguity resolution on position.