Equipment Suppliers

The radio-modems used for the radio links between the Bar Beacon and the RNLI Station, Hayling Island, were kindly donated by Wood and Douglas Limited, a Solent-based supplier of communications equipment.

The sensors on the Bar Beacon, the associated datalogger, and the software applications used to analyse the data, were supplied and installed by Campbell Scientific Limited

Emworx Limited on Hayling Island, have given advice on system design, built the web site and supplied hosting facilities.

Chimet Support Group is responsible for the design and development of the overall system, its project management, and the development of the software used for data control and presentation.

Sensors and Data Reporting

The Web site is updated every 5 minutes from the data collection site at the RNLI Station, Hayling Island

The link to tidal predictions (in the Latest Report page) is from the United Kingdom Hydrographic Office Position coordinates (latitude and longitude) are referred to WGS84 chart datum.

Tidal heights are reduced to Chart Datum, which is approximately the level of Least Astronomical Tide.

The following table shows briefly how the reported data is derived.

Measurement Sensor Sampling Frequency Averaging Reporting Interval
Wind Speed Anemometer Every second 5 minutes Every 5 minutes
Wind Gust Anemometer Every second Taking max of 3-second running average Every 5 minutes
Wind Direction Wind Vane Every second Vector addition over
5 minutes
Every 5 minutes
Air Temperature Thermistor Every second 5 minutes Every 5 minutes
Sea Temperature Thermistor Every second 5 minutes Every 5 minutes
Barometric Pressure Barometric
Pressure Transducer
Every
minute
5 minutes Every 5 minutes
Tidal Height Pressure Transducer Every second 5 minutes Every 5 minutes
Wave Height(average)
*Note 1
Pressure Transducer Every second 15 minutes Every 5 minutes
Wave Height(maximum)
*Note2
Pressure Transducer Every second 15 minutes Every 5 minutes
Wave Period
*Note 3
Pressure Transducer Every second 15 minutes Every 15 minutes

*Note 1 - Wave height is calculated by subtracting the minimum water depth from the maximum water depth. An average is then taken over 15 minutes.

*Note 2 - Maximum wave height is calculated by subtracting the minimum water depth from the maximum water depth. The maximum is then recorded.

*Note 3 - Wave period is calculated by taking a Fast Fourier Transform on 512 consecutive samples of the water depth. A spatial maximum is then performed on the resulting histogram. This gives the bin with the greatest frequency. The frequency is calculated from the bin number. Wave periodicity is the reciprocal of this. The number of samples has been limited by the available battery power at the Bar Beacon.