The antennas, which can be seen in the dunes, are part of an ocean radar system, which provides real-time data for ocean currents, waves and winds over a large area. Thus, ships with a great depth approaching the port of Rotterdam can get information about the flow conditions in the waters off Hoek van Holland. This reduces the risk of running aground.


The measurement principle is based on the fact that the ocean waves reflect high-frequency signals. The system has a transmitter with very low power and emits high frequency of 16,15 MHz towards the sea. Although these systems are historically known as “coastal radar”, they have little in common with the conventional navigation radars. The range of the systems is generally much longer, in this case 60 km, and it takes only several minutes to get one data set. The transmitted signal is not pulsed with high energy, but it is a very weak continuous signal of just a few Watts, like that of a mobile phone.
These signals are emitted from four transmitting antennas, reflected from the sea surface, and detected by the twelve sensitive receiving antennas. From these received signals, the main electronic component calculates the direction and magnitude of the flow.

To create two-dimensional current maps you need two systems at a distance – like the ones here in Monster and Ouddorp. The measurement of the metocean parameters can thus be land-based, e.g. without the use of buoys. There are many years of experience and many investigations compared to buoy measurements (ADCPs, etc.).

The system requires a preferably coastal location on the beach, on the dyke or on a steep coast. In general, a series of 4 to 16 individual antennas are used which, depending on the requirements, are between 1.5 and 3 m high and can be easily inserted into the environment. The measuring station itself is protected against environmental influences in a measuring container or locally available buildings. The connection to the antennas is via cables so that the container does not necessarily have to stand on the beach, but can be built at some distance without disturbing influence on the landscape.

The two systems installed in Monster and Ouddorp consist of four transmitting antennas, twelve receiving antennas and one electronic main component.

For Rotterdam, the measurement data are combined with data from a computer model of the flow and ensure that the expectations of this model are reliable. This computer model ensures that there is always information available; also, when measurement is temporarily not possible. This information will be made available to the captains of incoming and outgoing ships as well as to the public.

Coverage area

The cover area extends far beyond Maasvlakte and covers an area west and north-west of Maasvlakte.

The measurement results can be viewed and accessed on the website www.waterberichtgeving.rws.nl.


  • 4 transmitter antennas with 7.5 W each
  • Frequency range 16.10 – 16.25 MHz
  • 12 Receiving antennas
  • Measuring time: every 8 minutes 50 seconds
  • Grid resolution: 1 x 1 km
  • Number of measurements per hour: 4
  • Range: 60 x 40 km