Topical matters

Positioning, Navigation and Timing


In ITU-R M.823-3, on the technical characteristics of differential transmissions for Global Navigation Satellite Systems (GNSS), IALA was assigned the task of coordinating the allocation of identification (ID) numbers to radio beacon transmitting stations and reference stations. The ID numbers enable the user equipment to identify the station it is receiving and also select particular stations when required. It is essential that the ID numbers be allocated in a way that prevents duplication and ambiguity. A scheme was devised by the IALA Radionavigation Committee, now the task is transferred to ENG Committee, to achieve this and a procedure was established whereby an administration requiring ID numbers could select them from an assigned block and notify IALA so that the choice of numbers could be checked and confirmed.

IALA also maintains a list of all relevant characteristics of known DGNSS stations, including ID numbers. The input to the master list will be prepared by each Administration. IALA will provide an electronic template to be used for initial entry of station data and subsequent updates to the data as required.


To ensure that DGNSS ID numbers are allocated and the Master Station List is maintained and updated in a timely and efficient manner, the following procedure has been devised.

1.    Administration refers to the IALA website and selects unused ID numbers from the national or regional block as applicable. If no suitable number appears to be available, the template, shown in Table below, should be submitted with a query in place of the ID numbers.

2.       Administration forwards the template to the IALA Secretariat for action.

3.      The IALA Secretariat forwards the template within 5 working days to the Chairman of WG3 (PNT) of the ENG Committee to verify that the ID numbers are appropriate. If an inappropriate or no number has been selected, then the Chairman of WG2 of the ENG Committee liaises with the Administration to resolve the situation.

4.     The Chairman of WG3 of the ENG Committee is to return the annotated template to the IALA Secretariat. The IALA Secretariat is to update the Master Station List on the IALA website within 5 working days and notify the Member State of the status of their request.

This procedure is shown in Flow Chart below. The Member States are requested to bring this information to the attention of competent authorities and radio regulatory bodies so that they become aware of the aforementioned scheme and the necessary procedures put in place to avoid ambiguity or duplication of ID numbers.


[Table] Template for Allocation of DGNSS ID numbers

Field Attribute
Station name Max. 9 characters
Transmitting Station ID Integer, 0-1023
Reference Station (RS)1 ID Integer, 0-1023
Reference Station (RS)2 ID Integer, 0-1023
Latitude DD MM ; North / South
Longitude DDD MM ; East / West
Nominal Range (Km)
Field Strength at Nominal Range (μV/m)
Official Operational Status Test or Preliminary / Fully operational / Not in operation*
Integrity Monitoring Yes / No
Transmitted Message Types
Radio frequency (kHz)
Bit rate (bits/s)
Datum WGS-84 / PE90 / Local Datum

* DGNSS station that is no longer in operation will remain on the Master LIST for 6 months from the date of termination of service

[Flow chart]
  Process for Allocation of DGNSS ID Numbers

Scheme for allocation of ID numbers to DGNSS transmitting and reference stations

TransmittingStation ID Geographical Area ReferenceStation ID
000-099 Russia, Ukraine, Azerbaijan 000-199
100-199 Indian Ocean 400-599
200-299 Africa 200-329
300-399 Mediterranean/North Africa 400-599
400-599 Northern Europe/Eastern Europe/Baltic 600-999
600-699 North East Asia 600-799
700-739 Oceania 000-119
740-799 South East Asia 120-209
750-970 North America 000-439
971-980 Central America 440-459
204-278 South America 460-479
986 French Guiana 475
1000-1023 Pacific Ocean 300-399
540-599 Spares
Europe, Africa 900-1023
Americas 560-949
Asia, Australia, Pacific Ocean 800-1023



1. ITU-R M.823-3 “Technical characteristics of differential transmissions for global navigation satellite systems from maritime radio beacons in the frequency band 283.5-315 kHz in Region 1 and 285-325 kHz in Regions 2 and 3” (2006)

2. RTCM 10402.3, RTCM Recommended Standards for Differential GNSS Service (Version 2.3)

3. RTCM 10401.2, Standard for Differential Navstar GPS Reference Stations and Integrity    Monitors (RSIM)

4. IALA Recommendation R0121 On the Performance and Monitoring of DGNSS Services in the Frequency Band 283.5 – 325 kHz (Ed. 2.0, May 2015)