Advance notice of GPS Week Number Roll Over (WNRO) event impacting Lassen iQ receivers on 29th May 2021.

This is an advance notice that some of the older (white) GPS receivers we have supplied in the past will stop providing accurate dates after the 29th May, 2021 unless remedial action is taken in advance.


This WNRO event will affect Lassen iQ receivers which, on the 30th May 2021, will roll back to report a date of 14th October 2001.


You can use the guidance on to identify if you are using a Lassen iQ receiver

Options for remediation:


DM24 digitisers


If you are using the Lassen iQ GPS receiver with a DM24 Mk3 digitiser, you can do one of the following:


  • Update the digitiser with the WNRO firmware update for the Güralp DM24 Mk3 (this update will also address all future WNRO events including 2032 and 2038)

  • Replace the GPS unit with a new unit that is unaffected by the WNRO problem

  • Güralp can upgrade your receiver with a new PCB assembly. This will involve returning your receiver to the factory

  • Your local distributor may be able to upgrade your receiver with a new PCB assembly. This will involve returning your receiver to your distributor. Please contact your distributor to see whether they offer this service

  • You can purchase a "field upgrade kit" for your receiver, which will allow you to replace its existing PCB assembly with a new one which is immune to the WNRO problem



CD24 Digitisers


If you are using the Lassen iQ GPS receiver with a CD24 digitiser you must replace the GPS unit or upgrade the PCB assembly



Full details on all the options available can be viewed in the guidance here:

Previous WNRO event in 2019


You may recall that there was a similar issue with the WNRO event in 2019 which primarily effected a different model of GPS receiver (Lassen SQ), and which we communicated in some detail. It is therefore possible that you have already taken the necessary action to avoid the problems arising from the 2021 WNRO event, however, we strongly recommend that you review your equipment and firmware records to satisfy yourself that this is the case and that no further action is required.


Full guidance on the 29th May 2021 WNRO event and the remedial actions that should be taken can be found on our website including:

  • Advice on how to identify if you have a lassen iQ receiver
  • Methods for updating DM24 firmware
  • Actions to take if purchasing new GPS units for CD24 digitisers


For more information read the full guidance here:


Güralp Systems Ltd.
3 Midas House, Calleva Park
Aldermaston, Reading
United Kingdom

Tel: 01189 819056
Copyright © 2021 Güralp Systems Ltd. All Rights Reserved.

Please publish modules in offcanvas position.

This website uses cookies. You may decline the use of cookies for this website but it may impact your user experience. Click on the 'More information' button to find out more about the cookies we use.