sigma S6 WaMoS II Wave Radar

The sigma S6 WaMoS II Wave Radar System is a proven radar-based wave and surface current monitoring system developed by OceanWaveS GmbH.

In comparison to conventional wave rider buoys and current profiling devices that generate single point measurements, the WaMoS II offers the advantage of presenting this information for a broad surface of the ocean and in a richer context.moving waves

The sigma S6 WaMoS II's measurements are constantly refreshed, whether on a moving vessel or from a fixed location. This provides real time data relevant to the local operational area as compared to conditions reports at a closest available point of reference. 

High definition images of wave fields combined with numerical data and intuitive graphical reporting keep the operator well informed in assessing environmental risk and identifying safe operational windows.

As a complement to an existing sensor or as a primary system, the sigma S6 WaMoS II provides higher fidelity information with comparable accuracy, at lower lifecycle costs.

Proven Accuracy and Reliability

The table gives names and symbols of the major sea state parameters and the corresponding ranges and accuracy provided by sigma S6 WaMoS II. The numbers are derived from direct comparisons between sigma S6 WaMoS II and independent in-situ sensors (e.g. laser, buoy).

Environmental limitations: The imaging mechanism for waves in any kind of X-band radar requires a minimum wind speed of 3 m/s, otherwise the waves are not reflected in the radar. In addition, significant wave heights below 0.5 m can not be resolved by the system. Heavy persistent rain showers will also not allow for wave measurements, as those disturb the reflecting ripple waves on the sea surface and the radar reflections become very strong.




Accuracy**), ***)

2D‑wave number spectrum




2D‑frequency direction spectrum


0.035 - 0.35  Hz


1D‑frequency spectrum


0.035 - 0.35 Hz


Significant wave height


0.75 – 20 m*)

+/- 10% or +/-0.5 m

Mean period


4 - 20 s**)

+/- 0.5 s

Peak period


4 - 20 s**)

+/- 0.5 s

Mean wave direction


0 - 360°

+/- 2°

Peak direction


0 - 360°

+/- 2°

Integrated wave spreading


0 - 90°


Peak wave length


15 - 600 m**)

+/- 10%

1st peak period


3 - 18 s**)

+/- 0.5 s

1st peak wave length


15 - 600 m**)

+/- 10%

1st Peak direction



+/- 2°

2nd peak period


3 - 18 s**)

+/- 0.5 s

2nd peak wave length


15 - 600 m**)

+/- 10%

2nd peak direction


0 - 360°

+/- 2°

Surface current velocity


0 - 5 m/s**)

+/- 0.2 m/s

Surface current direction


0 - 360°

+/- 2°

*) There is no limit in estimating the wave heights, but up to now Hs of 14 m was the highest value measured with WaMoS® II.

**) These values indicate the typical range by using an antenna with 1.4s repetition time. But it depends very much on the radar hardware, the total time of measurement and therefore can vary for each individual installation.

***) Based on comparative wave measurements taking into account an equally distributed error.

In industry sponsored trials, data comparisons between the sigma S6 WaMoS II and wave rider buoys have independently verified its accuracy as well as the additional value provided in monitoring a full 360º range.

wamos buoy comparisonsigma S6 WaMoS II is presently supporting operational decision making applications including:

  • offshore construction

  • diver support

  • safe helideck operations

  • deployment and recovery of small vessels and shipboard equipment

  • navigation in extreme sea states

Long-term deployments in unmanned and remote coastal installations over periods of years is a testament to its reliability.

Wave and Surface Current Parameters

The sigma S6 WaMoS II measures and displays all of the essential wave field parameters including significant wave height (Hs) peak wave period (Tp), peak wave length (λp), peak wave direction (θp), as well as surface current speed (U) and surface current direction (θu).

To learn more please download the document A Technical Description of the sigma S6 WaMoS II Wave Radar System.


The WaMoS II Display

An example of the WaMoS display with the wave spectra down the left side with a drop down box showing the mean wave wave energy (frequency spectrum). wamos screen
This display shows the wave parameters down the side with a history of current speed and direction. current history
This display shows the standard wave spectrum and a current map from the optional High ResolutionCurrent module High resolution current display


radar on towerPerformance and Operating Range

The operating range of the sigma S6 WaMoS II extends to 4 km. depending on the X-band radar type and installation geometry.  The average range for vessel-based installations is approximately 3 km. Requiring a minimum wind speed of 3 m/s and an average wave height of 0.5 to 0.75 m, the system easily detects waves lengths from 15 m to 600 m and covers periods from 4 seconds to 18 seconds.   


Monitoring Changes in Sea State Conditions and Alarming

This series of wave spectra were collected over a 40 minute period. As the sea state changed there are several recognizable changes in the wave spectra.
As time elapsed the wave energy grew, the Hs become higher (4.0 to 4.8 M), the wavelength increased (10.2 to 10.8 sec) and the frequency decreased.
Taken from data collected onboard the CFAV Quest off the south east coast of Nova Scotia, Canada.
Sea state changes.


Sea state alarms can be set to trigger for three different conditions:

  • When the significant wave height exceeds a specified value.ocean waves

  • If peak wave lengths fall outside a specified range.

  • If the encounter angle between the wave system and the ship's course moves outside a specified range.

Data Sharing and Recording

An advanced recording capability enables operators to review and confirm conditions in the event of an incident or regulatory inquiry. WaMoS II can be exported for integration in other data base, meteorological, and environmental systems. It can also provide NMEA output to conning and decision support systems.

High Resolution Current

This optional module displays high resolution current (HRC) for deep and shallow waters.  Surface current maps are generated in a grid structure by the HRC software.



Imaging of Individual Waves

This optional functionality displays individual waves in deep and shallow waters. Post-processing is required, and more information is available on request.

Individual waves individual waves


Research Papers and Conference Presentations

The sigma S6 WaMoS II has been used in a wide variety of oceanographic research to increase the knowledge base about waves and surface currents. Following is a partial list of the available publications. Click on the title of the article to download a copy.

Estimation of the Significant Wave Height with X-Band Nautical Radars- Jose Borge, Katrin Hessner, Konstanze Reichert. OMAE 1999.

Estimation of Sea State Directional Spectra by Using Marine Radar Imaging of Sea Surface. Jose Borge et al. OMAE 2000

Detection of Extreme Single Waves and Wave Statistics., Rosenthal et al. 2003. Maxwave 2003

X-Band Radar as a Tool to Determine Spectral and Single Wave Properties. Reichert et al. Presentation to 2004 Wave Hindcasting Conference.

Ground based remote sensing as a tool to measure spatial wave field variations in Coastal Approaches. Reichert and Lund. J.CoastalRes. 2007.

High Resolution Current & Bathymetry Determined by Nautical X-Band Radar in Shallow Waters. Hessner and Bell. Oceans 2009.

Coastal Mapping Around Shore Parallel Breakwaters. Paul Bell. Hydro International 2009.

Ocean Surface Winds Retrieved from Marine Radar-Image Sequences. Dankert et al. Intl Geoscience & Remote Sensing Symposium, 2004.


Practical and Versatile Solutions

Rutter sigma S6 technology connects to most commercially available marine radars, enabling customers to extract additional value and effectiveness from their existing radars. Should it be required, Rutter provides the option of supplying a dedicated high performance radar as an input sensor. As with all Rutter sigma S6 product lines, the WaMoS II wave radar system can be combined with any of our other systems to meet your needs:

Wave and Current Monitoring Systems
WaMoS®-500 WaMoS®-300
Features and Options:  
High Resolution Current (HRC)  
Wave and Current Analysis and Wave Spectra (WaMoS)
Screen Recording- Screen Shots (.jpg &.png) and Video (.avi)
Continuous Operation While Underway  
Multiple Remote Clients
Average Surface Current
Shallow Water Bathymetry  
Sea-State Alarms (3)  
Fixed Sites
Moving Vessels  

Note: All models accept standard serial/network inputs from navigational instruments (NMEA 0183)         including AIS, anemometer, echo sounder, speed log, GPS, and gyrocompass

Download the sigma S6 WaMoS II Wave Radar Product Description by clicking here.

Download a PowerPoint presentation showing the various animations mentioned above working.


Information about acquiring the sigma S6 WaMoS II Wave Radar system, end user training, product support, product combinations, performance modeling, product references, and reliability measures csea-image logoan be provided by: