Marine Life and Photogrammetry

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. Today we will be looking at how Photogrammetry can work in the documentation of marine life.

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.

Schooling pollack on the wreck of the Black Hawk – schooling fish indicate a wreck is nearby

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 of Marine Life

Recording species, type and density is a key part of marine science. It is used to measure the health of the marine world. Can photogrammetry be an inter-disciplanry tool to assist in the preservation of marine life?

In 2017, divers discovered this tiny wreck. A First World War-era German motor launch from the High Seas Fleet, in Scapa Flow, Orkney. 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, someone has removed these artifacts, and we have lost their context 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.

Marine Life and Photogrammetry
Marine life alongside port holes and the engine block of the wreck

Common sea urchins, whelk egg cases, two squat lobsters (look for the claws) and fish schooling inside the engine block are all visible.

Although none of the species above are typical food in the UK, we export whelks as a delicacy to South-East Asia. Moreover, Fishermen caught and landed an estimated 19,464 tonnes of whelk in 2019. These are significant volumes and the humble whelk suddenly jumps in economic importance and value.

Determining the number of whelks in an ecosystem and the sustainable catch limit will help shape policy decisions. This is an example of how photogrammetry is useful for the document of marine life.

Knowing the quantity of whelk eggs in an ortho photo becomes more valuable.

The ortho mosaic is visible here. Be sure to zoom in:

Summary of Marine Life and Photogrammetry

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. Everyone – including non-divers – can explore, investigate, ask questions and deliver quantifiable answers.

Marine Life and Photogrammetry
Starfish with two squat lobster. Levels of detail are typically 1mm per pixel

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.

In fact, we have some really diverse and unique habitats right on our doorstep. Although, few remain aware of just what lies beneath the waves. The economic value supports communities and livelihoods and puts food on the table.

Moreover, accurate and reliable photogrammetry can not only share the beauty but guide the policy. In conclusion, Policy must preserve and protect this fragile environment.