Furuno warns of early problem with GPS Rollover

Malcolm Latarche

Malcolm Latarche · 11 February 2019


A software issue with many models of GPS across manufacturers is expected to occur in week commencing 6 April this year but Furuno has issued a notice saying that some of its models may be affected even earlier.

The problem relates to the fact that some models of GPS will automatically reset the time function after 1024 weeks operation and report wrong time against position. This may in turn affect systems that have an integral GPS or take a feed from an affected GPS system. The Furuno notice is repeated below but ships with other systems should be taking action to avoid similar problems by contacting the manufacturers of equipment and systems on board.

The Furuno announcement says:-

“It is regretful to announce that there is a possibility that some of our GPS products (please see the list below) may face GPS errors after the 17th of March 2019, due to the problem of GPS week number rollover. If you happened to spot any errors on the equipment listed below, we would like you to take the following countermeasures to resolve the problem. If the problem persisted after having taken the countermeasures, please consult with our sales representative closest to your location. We sincerely apologize for all the inconveniences caused.

1.List of equipment that may be affected by the GPS week number rollover

Rollover Occurrence Date: 2019/03/17

Type of Equipment Model

Current Indicator CI-1000

Inmarsat-C mobile earth station FELCOM12 / FELCOM12-ALC

Radar plotter sounder RS-1000A / RS-1000C / FRS-1000A / FRS-1000B / FRS-1000C

Colour video plotter GD-280 / GD-380 / GD-680

GPS plotter GP-1600 / GP-1810 / GP-1610C / GP-1650 / GP-1850 / GP-280 / GP-3210 / GP-380 / GP-680

GPS/plotter/sounder GP-1600F / GP-1650F / GP-1810F / GP-1850F

DGPS plotter GP-1650D / GP-1850D

DGPS plotter/sounder GP-1650DF / GP-1850DF

GPS receiver GP-310B (serial no. 3452-4870 to 5686)

GPS navigator GP-31

DGPS navigator GP-36

2.Natures of the error and its cause

The GPS system is synchronized to a different time scale than Coordinated Universal Time (UTC) and calculates time by counting the number of weeks up to 1,023rd week. After week 1,023, the week number count is reset to zero. This is called "GPS week number rollover". Subsequently, the erroneous date information on the GPS receiver clock may result in instability in positioning, causing position errors, including failure of GPS position acquisition, etc.

3.Procedure for checking the integrity of the equipment and counter measures to be taken

Please carry out the following counter measures:

Since the nature of the problem of "GPS week number roll-over" is the erroneous date information on the receiver clock, the equipment that does not require date information would be unaffected by the problem in question. If, by any chance, the positioning performance became instable, you would be able to resolve the problem of positioning integrity by cold-starting the equipment through the operating menu. Please note, however, that even though you regain the GPS position acquisition, the date information cannot be restored merely by cold-starting.

If the positioning integrity is not restored after cold start, the problem may stem from the failure of the equipment, not from GPS week number roll-over. If such is the case, please consult with our sales representative closest to your location.

If you wish to restore the date information, you will need to replace the GPS receiver within the equipment for value. Also, please note that the above list of equipment includes some models whose maintenance service provision period has been expired.


If the GPS product is interfaced with any of the following equipment and systems, the countermeasures would have to be taken, for the date information is utilized by the interfaced equipment and systems.

GMDSS radio installation, incl. internal GNSS receiver of Inmarsat-C terminal

Ship Security Alert System (SSAS)

Vessel Monitoring System (VMS)

Equipment that displays route information such as ECDIS

Voyage Data Recorder (VDR)

Automatic Identification System (AIS)

Other equipment and systems that utilizes the date information from GPS receiver clock

For further information and consultation, please contact your nearest point of contact of FURUNO.

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