1. Remote integrity monitoring of DGPS by use of AIS infrastructure
Tom Braute
Norwegian Coast Directorate
Presentation of a cost effective system for remote integrity monitoring of the Norwegian Coastal Administration DGPS service.
The system use the infrastructure established for the Norwegian AIS network.

2. Overview Today: From 2007: Rationale for RIM system
Local Integrity Monitoring (LIM)
Weakness of LIM
From 2007:
Local and Remote Integrity Monitoring (LIM + RIM)
Rationale for RIM system
Description of RIM system
Status and implementation plans

3. Norwegian Coastal Administration DGPS service
DGPS radiobeacon
Norwegian Coastal Administration DGPS service
The Norwegian National Coastal Administration DGPS service is broadcasting differential GPS corrections from 12 maritime radiobeacons along the Norwegian coast.
The DGPS service offers the mariner a position accuracy of 10 meters or better (1-3 meters in practice). The service also gives alarms on GPS failures (integrity alarms).
The costs for establishing and operating the DGPS service is granted by the Ministry of Fisheries and Coastal Affairs.

4. Local integrity monitoring
A Norwegian National Coastal Administration DGPS station comprises
2 reference stations
1 local integrity monitor
1 MSK modulator
1 Front-end PC
Central Monitor
periodically downloads alarms and statistics from each DGPS station
tool for verifying operational status

5. Weakness of LIM system Logging of statistics Verification of service
Monitor data for several hours occasionally lost
No monitor data → unusable period
Verification of service
No information if contact to DGPS station is lost
Must contact users directly

6. Rationale for RIM system
Additional source to LIM for information on
Current operational status
Statistics → improved documentation on signal availability
Improving today’s LIM might be wasted
Will the future DGNSS include LIM at TX sites?
RIM system can easily be adapted to future DGNSS
Use of AIS infrastructure  cost effective implementation
Independent to LIM infrastructure
Each RIM site can monitor 2 DGPS stations
RIM software based on AIS DGNSS software

7. Tasks for DGPS RIM
The primary tasks for the remote integrity monitor (RIM) are:
Perform integrity measurement of the DGPS data broadcast from DGPS stations
Generate alarms when integrity measurements exceeds certain alarm thresholds
Generate performance statistics for the DGPS stations which are monitored

8. Norwegian Coastal Administration AIS network
DGPS radiobeacon
AIS shore station
Norwegian Coastal Administration AIS network
AIS shore station with DGPS RIM
RIM locations
The Norwegian AIS network
comprises 35 AIS shore stations
operational service from early this year
The AIS network provides an infrastructure is which is ideal for remote monitoring of the DGPS service.

9. Description of RIM system
Configuration
DGPS RIM at 8 AIS shore stations
DGPS RIM communicates with DGPS central monitor by use of AIS IP-network
Modified AIS Base Station Controller (BSC)
GPS and DGPS receiver
RIM software

10. AIS shore station with RIM
The RIM functionality will be an integrated part of the Base Station Controller (BSC) of which there is one unit per AIS shore station

11. Status and plans for RIM system
8 AIS shore station sites with modified BSC HW
Prototype RIM software for BSC developed and tested (demo project with Kongsberg Seatex AS)
Further work (2006)
Operational RIM software for BSC
Upgrade DGPS central monitor system to utilize RIM alarm/status
Configure IP-network to safely share bandwidth between AIS and RIM system

12. Thank you for your attention !!