A
recent development by Ohmex is the addition of a radar tide sensor option which
can replace the pressure sensor to enable significant wave height and wave
frequency to be measured. The standard pressure sensor provides a very reliable
and robust source of tide height but is not suitable for wave measurements as
there is attenuation caused by the variable depth of the sensor below the
surface. Using a radar sensor ensures that surface measurements are absolute and
there is no attenuation or adjustment required for water density and atmospheric
pressure. The extremely short 'K' band microwave pulses (24.05 - 24.25GHz) have
a very low emitted power that is unaffected by backscatter or noise in the
return path from the water surface. The new instrument firmware will sample tide
height over a user defined period and calculate the standard deviation of the
data, Significant Wave Height being normally derived as four times this
calculated statistical value. The standard radar sensor measures distances up to
15m or with the addition of a small stainless steel 'horn' this can be increased
to 35m with the same +/-3mm tollerance.
The transmission of 'live' environmental data to marine users has always
presented a problem. Conventional UHF radio links are mostly point to point with
high cost receivers, line of sight transmission limitations together with the
conjestion of non-licensed public wavebands resulting in unreliable data links.
Marine AIS represents a strictly administered VHF waveband controlled by precise
GPS timing, this provides a highly regulated capacity for transmission of a wide
variety of messages over an area up to 25 Km radius. These messages are seen by
all AIS recievers within the broadcast area including low cost receive only
devices and can be decoded by standard AIS display software.
The AIS TideMet system is particulay suited to offshore energy sites where the
environmental information is required by a wide variety of marine users, AIS is
now a standard requirement for any work vessel within most offshore sites to
ensure that vessels can be seen and can see each other on position tracking
charts. An added bonus is that the TideMet is also a full type 3 Aid to
Navigation transponder which in addition to broadcasting environmental data can
respond to bases station requests or relay search and rescue (SAR) messages from
the emergency services.
A
recent development by Ohmex is the addition of a radar tide sensor option which
can replace the pressure sensor to enable significant wave height and wave
frequency to be measured. The standard pressure sensor provides a very reliable
and robust source of tide height but is not suitable for wave measurements as
there is attenuation caused by the variable depth of the sensor below the
surface. Using a radar sensor ensures that surface measurements are absolute and
there is no attenuation or adjustment required for water density and atmospheric
pressure. The extremely short 'K' band microwave pulses (24.05 - 24.25GHz) have
a very low emitted power that is unaffected by backscatter or noise in the
return path from the water surface. The new instrument firmware will sample tide
height over a user defined period and calculate the standard deviation of the
data, Significant Wave Height being normally derived as four times this
calculated statistical value. The standard radar sensor measures distances up to
15m or with the addition of a small stainless steel 'horn' this can be increased
to 35m with the same +/-3mm tollerance.
