Inchkeith Island - Aerial Map created from an orthophoto by UAV 365

An island drenched in history, tested by time, weather and warfare.

Inchkeith Island

A varied, 1,800 year history stretches across the island of Inchkeith, located in the Firth of Forth off the shores of Edinburgh.

Now a scheduled monument, the 57 acre island has been home to many uses through time.

From the shore, the most prominent feature on the island is the lighthouse, constructed in 1804 and still in operation.

The last major activity on the island took place during the 2nd World War, when around 900 people were stationed there to defend the Forth Bridges and the Rosyth Dockyard.

During this time, the existing defences were extended and expanded, and the island was transformed into a fortress. Gun emplacements, capable of anti air and anti ship defence, were placed in multiple locations, with supporting structures scattered across the small landscape.

Seen from the air, the assortment of boxy structures resemble a crudely created virtual environment, where structures and geography are juxtaposed against each other awkwardly.

What remains of those defences today are complex structures with underground systems similar to a warren or ants nest. Questionable construction techniques are in use everywhere, breaking away as the weather stretches their ability to resist collapse.

But the ruins still create a deeply engaging connection with the past. The larger structures tell their stories, drawing your curiosity and inviting you to ask questions about their previous roles.

UAV 365 were honoured to be able to experience and explore this fascinating place.

Read on to learn about the methods we used and the challenges we faced.

Project Goals

Goal:
Survey the 57 acre island.
Method:
The external survey was carried out using the DJI Matrice 210 V2 with a Zenmuse X7 sensor and various lens focal lengths.

The majority of the mapping flights were pre-programmed using the latest version of Hammer, a flight control application. It was not possible to cover all areas of the island using this software so for specific shots or sections that required flying in close proximity to the cliffs, flight control was handled manually.

Ground control points were deployed to ensure the final model was accurately geolocated and future comparisons could be made.

An overflight was also carried out using the DJI Phantom 4 RTK drone after the main mission concluded. This provided a supplementary dataset to measure geolocation data against.

Goal:
Survey four of the key structure groups present on the island.
Method:
Internal drone based photogrammetry was carried out using the Flyability Elios 2, and then combined with external drone and ground based photogrammetry.

Why did we use an internal drone instead of a terrestrial laser scanner? This will become clear in the next section.

The Challenge

The drone operation requires about 8 days on site.

Access is via a small boat which leaves the harbour at 7am and returns at 3pm.

When you arrive at the island, the boat will offer you up to a harbour wall with a solitary, weather beaten ladder. You and all of your kit need to safely ascend the ladder, ideally without dropping into the water below.

The island has no facilities in place; there is no power for battery charging; no fresh water; no formal shelter; and emergency medical help is a considerable distance away.

All island movement is on foot so you need to be ready to get the heart rate up as you manage the baggage of drones, batteries and supporting equipment between the two of you over the undulating and uncertain terrain.

From the 12th century onwards structures have been built up, buried, modified and degraded, and the ground you are walking on may be grass, rusted steel, a concrete roof or a concealed drop.

Almost all of the structures are unsafe, several of them degrading with every storm that hits the island.

There are no accurate maps or drawings to plan the underground flights – no one knows what’s in there and the chance of drone signal loss is high.

There is potential to disturb gulls and other sea birds, as well as seals who enjoy the waters around the island. If the gulls are suitably disturbed, they may attack your drone. In peak breeding season, thousands of birds call the island home – flying at this time is not an option, which eliminates the summer months.

For the month of November the beaches and harbour area shelter seals raising their young. Disturbing them can be catastrophic, as a stampede of adult seals moving suddenly to the water can cause severe harm to the young pups on the beach.

In the underground structures fragments of decomposing plastic, discarded by the wind, wait to throw themselves mercilessly at the internal drone, blocking the propellers or wrapping like an octopus around the protective cage, impeding airflow.

Decades of dust, accumulated from bird nesting and general degradation, are disturbed by the drone turbulence, reducing visibility and testing the dust proof lighting of the Elios 2 to the limit.

In the deeper chambers, the darkness is complete, and the silence is deafening.

If you lose the drone, finding it will not be easy.

It’s an eerie place, scary even, but completely and totally addicting.

Gathering the data

“Like photogrammetry, but bigger”

UAV 365 collected 400GB of 4K video and 7000 high resolution still images from Inchkeith.

This huge dataset formed the foundation for months of processing work, moving methodically through the structure groups to produce the 3D outputs shared below. The nature of access to site demanded careful attention to detail, to ensure that nothing was missed.

Data gathering at this scale in unexplored environments over sequential site days is a complex challenge. The coverage achieved for each flight needs to be accurately recorded in the field. The pilot also needs to hold a 3D picture of the sites visited in his mind, to avoid repeat flying and make the most of each battery cycle. In the unexplored underground passageways, the pilot needed to conduct a rapid assessment of the layout and still gather useful photogrammetry data.

Not a simple task, and combined with the usual stresses of internal drone flight (and the constant onslaught of plastic!) not a relaxing process to engage in.

Luckily, our Elios 2 pilot is calm, collected and rarely stressed.

Processing the data

Delivering the 3D results

Back in the office, the visual data was separated into subject groups and then the internal video was processed into still images. Approximately 11,000 internal and external images went into each structure group. Processing this quantity of data into 3D assets requires large amounts of time and patience.

Four separate 3D models were developed, combining data captured from the exterior and interior of the key structure groups.

The data was processed using Reality Capture software from Capturing Reality.

In addition, the aerial mapping data was processed to produce 3D assets of the island terrain. These assets were then developed into topographic information, providing contour maps, terrain models and some stunning orthophotography.

Sharing the Models

Tap the buttons below to explore the various models we created from the assembled data.

We are using the incredible Nira platform to allow you to explore the full size models.

Main Fortress Building

Full Size 3D Model

Northern Guard Tower

Full Size 3D Model

Officers Mess and Central Control Tower

Full Size 3D Model

Inchkeith Island

Full Size 3D Model

Reflecting on the Project

UAV 365 first visited Inchkeith in August 2020 – and since then the island has remained in our minds as we reflect on the task we faced, and the results we were able to retrieve.

Using the Elios 2 for structure modelling at this level of complexity and detail was, as far as we were aware, unheard of at the time and presented several challenges in data gathering and data processing.

With a final data tally of 650GB, this was the largest project we had worked on to date, and one which we remain enormously proud of.

While on the island we created the below video, to try and capture the atmosphere as best we could.

We hope you enjoy it:

For more information on this and other UAV 365 projects, please see our portfolio

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