RTK SERVICE

The OGS RTK service, which disseminates differential correction (phase and code), permits, adopting GPS&GLONASS technology, a positioning with a centimetrical precision in the Friuli Venezia Giulia area. The whole system is constituted by few permanent GPS receivers FReDNet and a process and distribuition server (caster).
The data are available through a generic, stateless application-level protocol: NTRIP (Networked Transport of RTCM via Internet Protocol) and the service, managed by the Centro di Ricerche Sismologiche - CRS, is free.
The NTRIP Caster addresses are the following:

Address Username Password Notes
158.110.30.81:2110 [user] [password] The following mountpoints are available:
  • Frednet single station;
  • A. Marussi single station
  • Frednet network solution:
  •     - NEAREST;
        - VRS;

    The service access ways to the real time positioning are the following:

    SERVICE DESCRIPTION
    SINGLE STATION The rover receives differential corrections from the single station (master) selected by the user. In this case, the server redirect data from the master station to the rover. More then one rover can access at the same time at the same master. In this case, the server increase data flow as many as the number of requests.
    The comunication form server to rover is monodirectional.
    NEAREST The working mode is the same of the 'single station' mode. In this case, the user doesn't need to know the master station for connecting. The caster will distribute automatically the differential correction from the nearest permanent station. Adopting this mode, the server need the rover approximate position.
    The communication server-rover is bidirectional.
    VRS The rover receive differential corrections from a Virtual Reference Station (VRS). The caster, using data coming from all the station of the network and the approximate rover position, calculates a 'network solution' which create a VRS near the rover (few km). The rover must send his approximate coordinates (NMEA format) to the server;
    the communication server-rover is bidirectional. Differential correction provided are compliant with the RTCM3.x protocol
    SLO -
    AU -

    The OGS caster further to the convention with Regione Friuli Venezia Giulia, disseminates also the single station differential correction of 'Rete A. Marussi', some of the Austrian EPOSA network and some sites belonging to the MPRI not-for-profit organisation and to the University of Ljubiana in Slovenia.
    All the real time services are distribuited respect to the new reference system ETRF2000(2008.0) scheme by Istituto Geografico Militare (IGM) to set of Rete Dinamica Nazionale (RDN).
    This system (ETRF2000(2008.0)) will be early adopted also in the services distribuited by 'Rete A.Marussi' which now use the reference system ETRF89.

    The user who connects his receiver to the caster has at his disposal several access points called mountpoint.
    The name 'mountpoint' identify:
    • the owner of the service (OGS or RAFVG)
    • the access service:
      • from single station if the name contain the name of the GPS station;
      • NEAR means from the GPS station nearest to the receiver;
      • VRS or FKP for network solutions;

    EXAMPLES
    OGS_JOAN The rover establish a connection in 'single station' modality with the OGS permanent site of JOAN.
    OGS_NEA The rover establish a connection in 'single station' modality to the nearest OGS permanent site
    OGS_FKP The rover establish a connection in FKP modality to the FReDNet Network
    OGS_VRS The rover establish a connection in VRS modality to the FReDNet Network
    RAFVG_BARC The rover establish a connection in 'single station' modality with the Regione Friuli Venezia Giulia permanent site of BARC.




    NTRIP
    To broadcast differential corrections is used the protocol RTCM (
    Radio Technical Commission for Maritime Services). The RTCM contains informations classifieds as TYPES. The RTCM can?t support modern service because doesn?t permits the contemporary access to more then one receiver to the same master. The RTCM data (differential correction) are broadcast through NTRIP protocol based on HTTP (Hyper Text Transfer Protocol). Ntrip is implemented in three system software components: NtripClients, NtripServers and NtripCasters. The NtripCaster is the actual HTTP server program whereas NtripClient and NtripServer are acting as HTTP clients.