DGNSS reference and integrity monitoring stations


Our solution is a DGNSS reference station designed for permanent installation as a stand-alone system or as part of regional GNSS infrastructure systems. The electronic components are built into a 19-inch rack module. The software offers full remote control and overview over configuration and status parameters. Multiple output of Radio Technical Commission for Maritime Services - RTCM corrections is supported.

Related Info :  DRS500/IMS500 description

DGNSS Overview

The basic concept of a DGNSS broadcast site is to collect GPS signal data at known Reference Station location, calculate the errors on those signals based upon known site information, and broadcast those errors (in the form of corrections) to ships fitted with Differential GPS receiver.The component performing this function is known as the Reference Station (RS).

Mobile DGPS equipment receiving the signals containing GPS data corrections from an RS then applies them to the GPS signals received at its location, yielding a more accurate GPS position. Also at the DGNSS broadcast site is a companion Integrity Monitor (IM) component that is responsible for validating the integrity of the correction computation and broadcast signals. When this IM component detects anomalies, it reports these conditions to the RS Component and to the Control Station.  

Reference Station Logical Diagram

The integrity information received by the RS is then injected into the correction information that it is broadcasting. In this way, the mobile DGPS equipment is protected from the vagaries of incorrect information. The above method of monitoring by the IM is known as the post-broadcast approach, which the RS has to broadcast an apology message and retransmit the valid correction. To overcome the above limitation, USCG has proposed a Pre-broadcast approach to ensure only valid correction is sent out by RS. 

This Pre-broadcasting approach has been accepted and approved by the RTCM special committee [ ref: RTCM STANDARD 10401.2, For Differential Navstar GPS Reference Station and Integrity Monitor (RSIM) Dated 18th Dec 2006, [ www.rtcm.org ]. The KSX proposed DGNSS system is based on the discussed RSIM v1.2 standard.