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

Further to earlier announcements, please see the below updated guidance for any issues relating to the week number roll over that occured on the 30th May 2021 affecting Lassen iQ GPS receivers.


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



CD24 Digitisers


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



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: +44 1189 819056
Copyright © 2024 Güralp Systems Ltd. All Rights Reserved.
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.