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15 April 2019

Support Update on GPS Week Number Roll Over Issue

Update on GPS problem with Week Number Roll Over for GPS units that pre-date 2015

Since we first alerted you to this matter last week, we have been working hard to identify what additional support we can provide to affected customers. We were only made aware of the issue on 27th March and the information provided was subject to subsequent changes. We now have more clarity on the implications for our systems.

DM24 Mk3 Patch

For DM24 Mk3 digitisers and integrated instruments (manufactured since 2005) we are now working on a patch and we have high confidence that this will work. If you are unsure which DM24 digitiser you are using, view our guidance on 'Distinguishing between a Mk2 and Mk3 DM242 digitiser'.
There will be some limitations to our provision of the patch:

It will only be possible to apply the patch to systems that are on-line if they have an integrated EAM. Digitisers without an EAM will need to be updated on site. We cannot guarantee that a remote update will always be possible.

For any customer who needs to eliminate uncertainty, our advice is to swap the GPS hardware now. You can find more information on our guidance note.
As soon as we have tested the patch, we will post an update with instructions on how you can apply it. If you would like to be added to the distribution list to receive this information by email, please send a request to

Other Affected Systems

Currently we do not expect to be able to provide a patch for DM24 Mk2 or CD24 systems. For both of these types of systems we advise a GPS hardware swap as the best solution.

Further Updates

We will continue to update the GPS NWRO guidance note on our website with our latest advice.
We are aware that this situation provides some logistical challenges for our customers and we apologise for any inconvenience caused as a result. You may have seen in the media that this situation is widespread amongst earlier GPS units supplied by a number of different manufacturers.
The Güralp Support Team



For urgent enquiries please call 020 3727 1000 and speak to Fergus Wheeler, Louisa Feltes or Jess Gill. 






Güralp Systems Ltd.( is a leading global provider of sophisticated seismic monitoring solutions used to understand natural seismological events such as earthquakes, aftershocks and volcanos, as well as induced seismic events, or seismic signals, resulting from human activity.

Our solutions are used in research, civil and industrial applications to increase understanding, optimise processes and to protect people and the environment. Our equipment is installed in all major ocean basins and across all continents worldwide.

Our instruments range in performance from very low frequency, very low noise for global seismology to high dynamic range instruments for local, strong motion monitoring. Our sensors and can be supplied for deployment at the surface, in boreholes and on the ocean bottom. We also provide data acquisition equipment, power and communication accessories and data interpretation software.

Our services include installation and commissioning; network operation; repair and maintenance services; data processing and interpretation.

Headquartered in Reading, in the UK, we have been operating for more than 30 years and have established a global network of distributors who provide local customer support and sales services.





Guralp Systems Limited
Midas House
Calleva Park

Tel: +44 118 981 9056
Fax: +44 118 981 9943