The system uses information obtained from the on board X-band radar to measure the ship’s speed with greater accuracy which is 0.5 m/sec that is 0.97 knots. The site mentions that this is 1 m/sec or 1.94 knots for Doppler logs but this is in reality much better. For instance the accuracy of a Wärtsila speed log over ground is ± (0.04 kn + 0.5 % of resulting speed) and the speed through water ± (0.1 kn + 1 % of resulting speed).
They claim that also ocean currents can be measured. In principle if the speed of the vessel increases that could be due to a stern current and the speed could be decreased and so fuel saved. You could even automate that to maintain a constant speed…
If you are looking for real accuracy you can better install a GS-100 Furuno satellite speed log with an accuracy of about 0.02 knots.
On top of that it also provides other useful information:
Offers transverse speed at bow and stern position, as well as longitudinal speed
Provides transverse speed at any position of the ship utilizing the built-in satellite compass
Delivers roll, pitch and angular information for navigation equipment such as Radar, ECDIS and AIS.