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Rough sea at Mid Channel Rock

The time and date on this website should be checked to confirm the data is live.

This station is installed on the Mid Channel Rock Lighthouse beacon just off St Anns Head at location 51° 40.315 N 5° 9.826 W. It is owned and maintained by Milford Haven Port Authority.

Data is brought back to land once every minute using a wireless radio link. Primary retries in the event of a failed download are attempted thereafter at 5 minute intervals until the link is re-established.

A Campbell Scientific CR800 datalogger captures data from the various sensors.

A Vega Vegapuls 61 radar unit provides water level, wave height and wave period information installed at a height of 22 metres above chart datum.

A Gill Windsonic M provides primary wind speed and direction readings, with a Vector Instruments A100 Anemometer and W200P Windvane backing this information up. These sensors are located at a height of 24metres above chart datum.

A Campbell Scientific CS215 sensor provides temperature and relative humidity readings installed at a height of 23 metres above chart datum.

Local chart datum is -3.71m at Milford Haven see National Tidal and Sea Level Facility for more information.

The following units are used at this station

Calm sea at Mid Channel Rock
  • Wind Speed readings are in knots
  • Wind Direction readings are in degrees
  • Temperature readings are in degrees celcius
  • Humidity readings are in percent
  • Dew Point readings are in degrees celcius
  • Water Level readings are in metres above chart datum
  • Wave Height readings are in metres
  • Wave Period readings are in seconds


15-05-14 0900hrs Vega Vegapuls 61 downward firing radar unit installed on Mid Channel Rock pole this morning.
20-05-14 1445hrs Sent new program to Mid Channel Rock datalogger 20-05-14 Rev18 which has new calculations, including gain and offsets to ensure the water level is calibrated in theme with the jetty at Gorsewood Drive. The calculations used for this are derived from predictions based on the tidal diamond at Dale Roads and then at Milford Haven to ensure we are as accurate as possible.
16-06-14 1730hrs Sent new program to Mid Channel Rock datalogger 16-06-14 Rev19 which has new wave height calculations including a 15 minute average. The 15 minute average is now applied to the home page and all graphs showing peak wave height as well as average wave height.
01-07-14 1535hrs Sent new program to Mid Channel Rock datalogger 01-07-14 Rev20 which has tidied up the data table ready for accepting calculations for wave period shortly. There have been a few 'blips' of the wave height information during the past week as the manufacturers have been making some tweaks to the radar to prevent problems during heavy rainfall events.
15-09-14 1625hrs The past week has seen several sets of program data being sent to the datalogger at Mid Channel Rock as we try and get calculations for wave period working correctly. Unfortunately as a knock on to this, it upsets the wave height graph for up to 15 minutes each time a new program is sent to the logger while the system restarts itself. Further updates will happen over the next few weeks as we aim to change out the datalogger ready for winter.
10-11-14 1900hrs Wave period calculations now applied to home page and graphs. Unfortunately we have not been able to get out to the datalogger before autumn/winter arrived which means we are still seeing some "blips" with readings from the radar in certain weather conditions / sea states.
20-04-15 1430hrs A replacement datalogger has been installed today with all internal wiring refreshed. We are hoping that this should start to clear up the occasional blips on the wave height readings during periods of bad weather.
24-04-15 1240hrs We've been seeing some erratic readings on the wave period since the new datalogger went in to place this week. A new program has now been sent and should tidy up the graph + give a more sensible/accurate reading too.
09-05-16 1544hrs Unfortunately, due to an electrical supply problem, this station was completely offline between the 28th of April and 6th of May 2016 while we waited for a weather window to safely board the tower. A new Vector Instruments wind vane was installed on the 28th of April replacing the existing unit which was damaged during the winter storms.
18-11-16 1555hrs The temp/humidity sensor has been playing up this past week and has now finally given up completely. A new sensor will be ordered shortly and then installed at the next available weather window.
19-06-17 1445hrs New temp/humidity sensor now installed. Additional batteries also installed to take us through the next winter period.
26-06-17 1200hrs The radio link between Mid Channel and the main land has failed. Replacement parts are on order to get the system operational again as soon as we can.
12-07-17 1400hrs A replacement radio link has now been installed and the datalogger is feeding all the information back to land again.
25-07-17 1100hrs Unfortunately the new radio link has failed. A visit to Mid Channel Rock this morning identified the problem and parts have been ordered. We hope to have it back in service as soon as the weather will allow.
07-08-17 2030hrs A replacement radio unit was installed this evening and the data from the past couple of weeks has just finished downloading. We will have another (different type of) radio unit to install in the next few weeks at which point we should have better redundancy in case of a similar failure again.
28-10-19 1600hrs Unfortunately there appears to be a problem with the power supply (during periods when the sun is shining) causing issues with both the wave sensor and sometimes the ultrasonic wind sensor. We have ordered replacement components which should arrive shortly and will then board when the weather allows, most likely second or third week in November.
16-11-19 2200hrs The wave sensor is struggling with the erratic power supply and giving non-consistent readings of wave period during periods when the sun is shining. The replacement parts are in and we hope to board the tower next week.
18-11-19 1700hrs After two visits to the tower today, most of the electronic components were replaced and a replacement wave sensor was installed later in the day too. This station is now operating correctly.
07-04-21 1700hrs This station was offline from 1630hrs on Monday this week due to a problem with the radio link between land and sea. The remote station was restarted this morning and the station is now back online and historical data has been downloaded without error.
29-10-21 1530hrs Added an SSL certificate to the site today. All links corrected to reflect https although search engines could take a while to catch up.
08-06-23 1130hrs Webcam installed on Watwick Tower looking towards Mid Channel Rock in the distance. Refresh rate 1 image per minute - this is currently in test so could go offline at any time.
22-11-23 1400hrs We replaced a number of batteries today at the tower and as a result the system reset and was offline for a couple of hours.
20-05-24 1620hrs The station has been removed from service while maintenance work is being carried out at Mid Channel Rock Lighthouse.

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