A key motivation for Indeximate is the mantra of “never delete the data”. We’ve suffered in past careers by observing really interesting data live but not having the disk space to store it, nor the desire to handle the practicality of storing lots of disks nor the easy ability to load and process lots of disks.
A key feature of our Scattersphere is the storage of all recorded DAS data in the cloud – uploaded by our Indeximation step. This gives us at our fingertips access to months of data – so what can we do with it?
This is where DAS gets exciting – the wide range of vibrations from near DC to infrasonic to ultrasonic is just incredible and hidden within that data is a wealth of data that is never really exploited. For example, if we are focussed on the health of the cable that we are monitoring we will profile this data for all things pertaining to integrity and/or the state of the deployment environment but ignore all the interesting data that might be in the watercolumn or the further seabed. And in there lies a wealth of further information that could be helping us unlock a better understanding of the oceans.
Thinking further, pulling the data to the cloud allows us to consider not just what is happening in the environment locally to the cable but potentially we can get an integrated view across multiple cables and start to build a networked picture of circumstances across both multiple distance scales as well as time scales – ultimately adding to our knowledge of global issues such as the effects of climate change – given enough time and data.
So what have we illustrated so far? We’ve been slowly publishing a lot of phenomenological observations (take a look at our Micro Learnings web page and our blog) whilst we’ve been busy at work looking after the health of the cable.
So what aspects are practically available from a data reuse aspect?
- Behaviour of the inter-tidal zone
- Temperature change
- Tidal Stream analysis (distinct from tidal analysis) / Ocean currents
- Lunar tidal relationships
- Wave Height information
- Shipping Movement, speed, location, classification
- Ocean Noise
- Turbine vibration / piling / noise transmitted through seabed
- Cetacean Monitoring / Marine Mammal Observations
- Piling Noise
- Human Terrestrial Activity on land sections – and this list just gets larger and larger – there’s no end really to what we might consider monitoring.
The growth of offshore wind is a huge opportunity – key of course is the transition to the electrical economy. In doing so we of course need to ensure that impacts on the environment are closely monitored – the monitoring of our cables provides an opportunity to do just that.
Take a look at the image below snapped from 4C Offshore.
The export cables, array cables and interconnects are not visible at this resolution but you can imagine – there’s a LOT. What do you think of when you see this? A net zero opportunity? A risk to the environment? An opportunity for energy security? A risk to energy security?
We look at and envisage the greatest subsea monitoring network that humans have ever created. Tens of thousands of km on the seabed – with a sensor every ten metres. Thinking in those terms allows us to imagine how this network could be used in 10 or 20 years. Our knowledge of the seabed and the marine environment will jump massively over the paucity of data that we have at the moment. Both for the benefit of users and those species who live there but also just for the sake of knowledge itself.
So to the examples given – what evidence do we have?
Ocean Currents
In this first image we are looking out over 3.5 days at a ~31km long stretch of cable in a rocky seabed in ~1km of water. The red regions correspond to modest local heating and the blue regions local cooling. Consider the green to be “ambient”. The temperature changes occur at roughly the same time across the length of the cable (with some local direction changes) so it suggests we are sitting broadside to local current. We are seeing warmer water flowing over in one direction followed by a period of cooling back to ambient. This is then repeated. Regularly.
Tidal Pressure on Cables
We also demonstrated from more predictable lunar tidal flows how we can measure diurnal variations associated with inflow and outflow of tidal regions of the coast. These have been cleaned of temperature data and what we are looking at here is the strain on the fibre from the ebb and flow of tide! This is the water pushing against the exposed cable causing strain – in excess of any temperature variation.
Human Activity
In this compelling, plaid like image we are looking at a cable on the shore, following a road heading towards the inter tidal zone and then waves coming in from shore. They are interesting of course, but the real area of interest is the strong red signals. Here we are looking at individual cars driving down the street which the fibre follows for about 1km. Looking over long enough we see daily and weekly patterns corresponding to the density of human activity. These can all be counted and profiled.
Shipping Activity
In this next image we see the passage of a ship along and crossing the cable as well as wave action, here the red colouring is from the engine noise of the ship, blue again is waves. These false colour images allow better meaning to be extracted from the data without difficulty.
Taken further and looking over a long stretch of time and space, one of our signature images below shows the transit and crossing of a vessel over the cable – here there’s a huge wealth of information that can be extracted: Vessel heading, cable beam pattern, engine noise, propeller noise, the acoustic noise of the ship hitting the swell (those green vertical chevrons).
Vibration of nearby structures
Back in January we posted on the extraction of fundamental vibration modes from turbines that we don’t go into but pass by… We are able to show how we could identify blade passing frequencies, the flexural mode of the tower (nodding) and gearbox / nacelle noise. Over the long term these could be used to identify tower fatigue (especially during non-producing, feathered periods) and items such as gearbox wear.
Wave Height
We know that our sensors are sensitive to pressure which makes them ideal for picking up longitudinal sound waves underwater. It also makes them exceptionally sensitive to changing water heights – i.e. swell and waves. With a small amount of ground truth data we can calibrate the response to wave height and produce an image of wave height variation with time across the whole cable as shown below.
