Running from the 22nd of July to the 7th of August, National Marine Week here in the UK is a celebration of the rich and diverse marine life we have in the seas that surround our island.
A highly dynamic environment, the marine world may be seen as a difficult subject to preserve in 3D, and that view is certainly correct for some subjects.
In the extreme movement will be so subtle yet so disruptive to photogrammetry the sensible option is to give up.
But there is a wide range of benthic and sessile marine organisms that play a vital role in the ecosystem. With a static lifestyle, these species are eminently suitable for photogrammetry. Even the creatures that move will often stay still, posing for the photographer and committing their presence to the 3D model.
Wrecks As Reefs
Shipwrecks are excellent subjects for photogrammetry and digital preservation. The ortho photos are excellent tools for investigation and interpretation and their value to science has been recognised by bodies such as the Royal Society of Photographers.
The wrecks themselves offer shelter and a fixed holdfast for marine life and over time turn into living reefs. This feature is apparent when diving in turbid water and reduced visibility, when the first clue the wreck is very close is the sight of schooling fish.
On a seabed of shifting sand the wreck becomes a haven of wildlife in a landscape that just isn’t suitable for many species. Wrecks add diversity.
Digital Preservation
Recording species, type and density is a key part of marine science and is used to measure the health of the marine world.
This tiny wreck, a First World War era German motor launch that was part of the High Seas Fleet interred in Scapa Flow, Orkney, was discovered in 2017. The first dive recorded the find in high detail.
Digital preservation recorded the location and type of key artefacts such as portholes and other non-ferrous parts. Regrettably, these artefacts have been subsequently removed and their context lost. The 3D model and ortho mosaic remain the single persistent record of their existence.
Alongside the brass fittings the camera also recorded the marine life that has become established.
Common sea urchins, whelk egg cases, two squat lobsters (look for the claws) and fish schooling inside the engine block are all visible.
Granted none of the list of species above is really thought of as food in the UK but the whelk is exported as a delicacy to South-East Asia and an estimated 19,464 tonnes of whelk were caught and landed in 2019. These are significant volumes and the humble whelk suddenly jumps in economic importance and value.
Knowing how many whelks are in an ecosystem, and how many can be sustainably caught, would be a critical piece of information to inform policy.
Knowing the quantity of whelk eggs in an ortho photo becomes more valuable.
The ortho mosaic can be seen in full here. Be sure to zoom in:
Summary
Photogrammetry for recording species like whelks can be a valuable tool for science. The evidence a visual record creates can share a powerful and important message and everyone – including non-divers – can explore, investigate, ask questions and deliver quantifiable answers.
Additional GIS tools such as Blue Marble Global Mapper can extract more value, with a rich set of vector drawing tools able to quickly assist measurement analysis.
Combining photogrammetry with geolocation and navigation tools – such as UWIS – the repeatability of surveys and their data can measure changes over time.
We have some really diverse and unique habitats right on our doorstep but few remain aware of just what lies beneath the waves. The economic value supports communities and livelihoods and puts food on the table.
Accurate and reliable photogrammetry can not only share the beauty but guide the policy that must preserve and protect this fragile environment.