Using sound to see through the sea

It’s all about the waves
Hydrography is a branch of applied science, which involves measuring the depth of water and identifying hazards that lie on the seabed.  Knowing the locations of things such as wrecks and rocks helps boats and people move safely at sea.

Normally you can’t see the seabed, so the way in which we measure the water depth is by using sound. We use a system called echo sounding. This works in a similar way to when you stand in a cave and shout out your name and hear your echo come back. The echo sounder is fitted on the bottom of the boat and ‘shouts’ at ultrasonic frequencies, and then listens for the response.

The sound of the sea
In simple terms it’s “speed = distance/time”.  The speed of sound in water is known (or can easily be calculated), and so by measuring the time it takes for the sound to return gives you the distance it has travelled to the seabed and back.
In reality it’s a bit more complicated than this as the speed of sound can vary – such as where freshwater from rivers meets the saltwater of the seas – and where the movement of the boat, tides, and the angle and type of seabed can all vary.

Using science to see clearly
However, using maths and physics, all the factors can be understood to give the super accurate answer we need of how deep the sea is. On our boats we use multi-beam echo sounders which give hundreds of readings every second.  This gives us detailed knowledge of the seabed and the chance to visualise what it looks like, just by listening to the sound waves coming back.
This is how we use the science of sound, to see through the sea.

If you want to see some of the latest data and images of the seabed around the UK, you can follow this link; www.gov.uk/guidance/inspire-portal-and-medin-bathymetry-data-archive-centre

Bob Kinnear, MCA Hydrography Manager.

Popular posts from this blog

PRESTWICK SEARCH AND RESCUE HELICOPTER SERVICE LAUNCH MARKED IN CEREMONY

Image
- Prestwick search and rescue helicopter base set to go live in January - The launch of the Prestwick civilian UK search and rescue (SAR) helicopter service was marked today (Thursday 17 December 2015) in a ceremony held at the new Coastguard SAR base at Prestwick Airport. Bristow Helicopters Ltd is operating the search and rescue helicopter service for the UK on behalf of HM Coastguard. The UK limited company was awarded the ten-year UK SAR contract by the Department for Transport in March 2013, representing a £1.9bn investment by the UK Government in the UK’s search and rescue helicopter service. By 2017 the service will be delivered from ten bases in all, strategically located close to areas of high SAR incident rates. The Prestwick base will begin SAR operations when crews begin receiving taskings from the Aeronautical Rescue Coordination Centre (ARCC) in January 2016. Bristow crews are delivering the UK SAR helicopter service on behalf of HM Coastguard with state-of-the-a...
Read more

Coastguard scoops stricken man from surging waves

Image
Senior Coastal Operations Officer Ryan Gray A man facing the threat of being dashed on the rocks by powerful waves was rescued by a coastguard who hauled him o ut of the surging water.   The alarm was raised at about 9.45am at Skippingstone beach, Bangor, on 1 October when a member of the public reported their concern for a person they had spotted struggling on rocks being pounded by the s e a .   The 999 call was picked up at Belfast Maritime Rescue Coordination Centre which swiftly sent Bangor Coastguard Rescue Team (CRT) and the local RNLI inshore lifeboat.   First on the scene was Senior Coastal Operations Officer Ryan Gray who, taking in the situation, quic k ly donned a personal float at ion device a ttached to a line.   As the sea surged, Ryan shouted a warning to the man before, seconds later , a wave picked the figure up and threw him to the shore.   The powerful surge carried him up the beach where Ryan was able to step forward and seiz...
Read more

BOSCASTLE FLOODS: TEN YEARS ON

Image
Boscastle Flooding 16 th August 2004 The storms of Monday 16 August 2004 saw three weeks worth of rain fall in one day. The resulting water began to be funnelled down the valleys surrounding Boscastle and soon the steep roads became rivers. By the time that the water reached the picturesque village, it had picked up enough momentum to become a raging torrent, sweeping into buildings, washing cars away and felling huge trees. Graham King runs the Witches Museum in Boscastle and was also the station officer for the Boscastle Coastguard Rescue Team at the time of the floods: “ My museum is situated next to the harbour near the river ,” says Graham “ and I can see the coastguard equipment store from there. Initially I was concerned that the vehicle and equipment were going to become stranded but I soon began to realise how quickly the situation was deteriorating and called Falmouth Coastguard ” From that point on the villagers and tourists stranded in flood waters were he...
Read more