Real-time differential corrections
The use of real-time differential correction is the most convenient and productive method for operating GPSGNSS surveys, as it allows the accuracy of measurements to be quickly and directly improved in the field.
The real-time positioning service provided by the FVG network distributes differential corrections both of code for navigation with a precision of metres (DGPS) and of phase for positioning with a precision of a few centimetres (RTK). The differential corrections are available both from the network and referred to the single master station.
Network solutions
Network solutions
VRS - Virtual Reference Station
The user sends the control centre their approximate location. Based on the data of the surrounding permanent stations, the network generates a virtual station next to the rover and sends them a personalised correction.
MAC - Master Auxiliary Concept
The network processing consists of estimating the differences between the data of one station (Master) and those of the others (Auxiliary), reducing all the observations to the same level of overall ambiguity. The information is packaged compactly and sent to the receiver rover without performing any spatial modelling. The user can choose the most appropriate manner to process the data received. The MAC mode requires the use of RTCM format in version 3.0 and later.
I-MAC - Individualized MAC
Is a method similar to VRS, but the corrections are referred to a real, non-virtual station.
Nearest
The user is sent the correction coming from the nearest permanent station to the rover.
Features
The feature of the differential corrections of the distributed network are summarised in the following table:
| Mountpoint | Solution type | Format |
| SingleBase_RTCM23 | Nearest - RTK | RTCM 2.3 |
| SingleBase_RTCM31 | Nearest - RTK | RTCM 3.0 |
| SingleBase_RTCM32 * | Nearest - RTK | RTCM 3.2 |
| VRS_RTCM23 | VRS - RTK | RTCM 2.3 |
| VRS_RTCM31 | VRS - RTK | RTCM 3.1 |
| VRS_RTCM32 * | VRS - RTK | RTCM 3.2 |
| VRS_CMR | VRS - RTK | CMR |
| MAC_RTCM31 | MAC - RTK | RTCM 3.1 |
| IMAC_RTCM3 | IMAC - RTK | RTCM 3.1 |
| IMAC_RTCM32 * | IMAC - RTK | RTCM 3.2 |
* includes the GALILEO constellation.
All the mountpoints listed above require the rover receiver to send an NMEA string (GGA position) to identify its position. The “SingleBase” mountpoints do not provide a network solution but are able, through the NMEA string provided by the rover, to pinpoint its position and transmit the differential correction referred to the nearest permanent station (Nearest) to the rover at that moment.
The mountpoints listed below refer to the single permanent stations, and provide solutions for both DGPS and RTK:
| Mountpoint | Solution type | Format |
| Ampezzo_DGPS | Single Base - DPGS | RTCM 2.1 |
| Ampezzo_RTK | Single Base - RTK | RTCM 2.3 |
| Barcis_DGPS | Single Base - DPGS | RTCM 2.1 |
| Barcis_RTK | Single Base - RTK | RTCM 2.3 |
| Bevazzana_DGPS | Single Base - DPGS | RTCM 2.1 |
| Bevazzana_RTK | Single Base - RTK | RTCM 2.3 |
| Cervignano_DGPS | Single Base - DPGS | RTCM 2.1 |
| Cervignano_RTK | Single Base - RTK | RTCM 2.3 |
| Gorizia_DGPS | Single Base - DPGS | RTCM 2.1 |
| Gorizia_RTK | Single Base - RTK | RTCM 2.3 |
| Pordenone_DGPS | Single Base - DPGS | RTCM 2.1 |
| Pordenone_RTK | Single Base - RTK | RTCM 2.3 |
| MoggioUdinese_DGPS | Single Base - DPGS | RTCM 2.1 |
| MoggioUdinese_RTK | Single Base - RTK | RTCM 2.3 |
| Tarvizio_DGPS | Single Base - DPGS | RTCM 2.1 |
| Tarvisio_RTK | Single Base - RTK | RTCM 2.3 |
| Trieste_DGPS | Single Base - DPGS | RTCM 2.1 |
| Trieste_RTK | Single Base - RTK | RTCM 2.3 |
| Udine_DGPS | Single Base - DPGS | RTCM 2.1 |
| Udine_RTK | Single Base - RTK | RTCM 2.3 |
Access to real-time positioning is realised via internet through an Ntrip caster (Networked Transport of RTCM via Internet Protocol) accessible at http://gnsscaster.regione.fvg.it:8080 or http://193.43.178.173:8080.
Access to the real-time service is free, but is regulated through access credentials (username and password) that can be requested filling the registration form.
To request credentials click
here.
It is advisable to refer to the operation manual of your rover or to your dealer, for the correct configuration of your receiver for the utilisation of differential corrections in real time via Ntrip.