Low Alititude Aerial Photography and Visualisation of Heritage - an MSc Project by Kieran Baxter
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Jarlshof - A computer generated film based on kite aerial photography of an ancient settlement site

This short computer generated film by Kieran Baxter tells the story of settlement at Jarlshof in the Shetland Islands. The film is based on aerial photographs taken from a kite-suspended camera with special permission for kite flying in such close proximity to Sumburgh Airport. The project was supported by Historic Scotland, who manage the site, and completed at Duncan of Jordanstone College of Art and Design, University of Dundee. Speculative reconstructions of lost buildings are based on kite aerial photographs from a number of other sites across Scotland - including Mousa Broch - and were completed in collaboration with Alice Watterson, Glasgow School of Art. The film is now on display in the museum at Jarlshof where it can be seen to full effect accompanied by an exploration of the site itself.

If you can't make it to the site today you can watch the film via YouTube (above) or alternatively on Vimeo (below). Scroll down to find more on the process behind the project, from kite flying on site to the reconstructed computer generated environment.

The process behind the project

As a main case study for my research into low altitude aerial photography as a tool for heritage visualisation I chose to use Jarlshof, an ancient settlement site in the Shetland islands. There are many reasons for choosing this specific site- it's dramatic location, complex four and a half thousand year chronology and juxtaposition of irregular prehistoric architecture represents a challenge for both survey and digital interpretation.

The main problem for kite flying at the site was it's location just 350 meters from the runway at Sumburgh, the main airport for the Shetland Islands. To take kite aerial photography within a controlled air traffic zone would mean working closely with the demands of the local Air Traffic Control.

The photograph and map above show the proximity of Jarlshof to Sumburgh Airport, in particular the approach to runway 33 which lies a few hundred meters from the site.

In the months before my field trip I was put in touch with the senior air traffic controller at Sumburgh. After establishing the details of the location, the height I would be flying at and the periods I would be flying for, permission was granted at the discretion of the air traffic controller on duty at the time, with the provision that I would be able to land all of my equipment on request if necessary. On arriving in Shetland I was shown the air traffic control tower which is directly across the bay overlooking Jarlshof. It was explained that the on-duty controller is always sat beside an assistant whom I would speak to in the first instance to request permission to fly.

Left: Visiting the air traffic control tower. Jarlshof is visible across the bay in the background
Right: As well regular fixed wing aircraft Sumburgh Airport is frequented by helicopter traffic.

Once the procedures had been established I had a five day window for kite aerial photography with each session dependant on weather and on the demands of air traffic. All told I requested to fly five times, all of them for one hour apart from one sunset session which lasted an hour and a half. Sometimes I was able to fly straight away while on other occasions I had to wait for a quieter period, although the longest I had to wait was an hour. On a couple of occasions I was asked to bring my my equipment down while incoming planes and helicopters passed within close proximity. Where flight paths were far enough away to not be an issue both the pilot and myself would be notified of each others activities and we would both continue. On each occasion I would call to confirm when I was done and my equipment was back on the ground.

Jarlshof is situated on a small outcrop near a sandy bay which would have been used a harbour throughout it's history. Sumburgh Airport is visible just beyond the beach in this kite aerial photograph.

Once again the changeable Shetland weather provided the opportunity for photographs in different lighting conditions, the harsh sunlight above being perhaps the least useful. In bright but overcast conditions I was able to capture some material more suitable for photogrammetry to supplement my previous work with pole aerial photography towards a 3D mesh of the site.

Iron Age broch and wheelhouse structures which lie beneath the 16th Century laird's house.

The ambient light created by overcast weather also provided the best conditions to photograph the broch remains in their entirety, a view which can only be obtained directly above the west corner of the ruined laird's house wall. As usual conditions were most illustrative towards sunset when a low light angle picked up the subtle topography of the site.

Left: Sumburgh Head, the southerly limit of Shetland lies just along the coast from Jarlshof.
Right: The kite and camera rig in action during patchy weather.
Below: In this general view the low light helps to distinguish the different layers of the site.

Low altitude aerial perspectives can provide a sense of depth and context which is often hard to achieve from manned aircraft. These unique shots are part of a wealth of material I was able to capture thanks to favorable weather and the generous assistance of the team at Sumburgh ATC, in particular Alan Smith who arranged provision for my visit. As well as making some very satisfying stills I hope to map some of these sequences onto my 3D representation of the site which in turn will be used as a basis for an interpretative reconstruction of the phases of habitation at Jarlshof.

Further thanks are due to James Gentles and Dave Mitchell who were able to advise based on past experience of KAP within controlled airspace.

Preperation for 3D Meshing

My first site visit was in mid December 2011 and although we were only on the island for three days the weather was kind and allowed for extensive photography for photogrammetry. The close proximity of Sumburgh airport to Jarlshof restricts kite flying so these images were captured using pole aerial photography.

The photograph on the left shows the remains of a circular Iron Age broch tower which has been eroded by the sea and later built on top of. The image on the right show the Viking portion of the settlement.

3D Mesh from Photogrammetry

Sequences of these low altitude aerial photographs have then been processed using Microsoft Photosynth to create point clouds which can be meshed using Meshlab. Below is a compariso between the point cloud and mesh covering the Iron age portion of the site and rectangular Laird's House.

Ten segments of photogrammetry created in this way were combined to make the completed mesh below, which remains un-coloured. It consists of 2.8 million vertices and was derived from around 2,500 photographs.

There are areas of missing data, in particular around the periphery of the site, in corners and the interior of the wheelhouses. Some of this data will be able to retrieved from unused photographs, some will not be able to be completed until a return visit to capture more. After some more iterations to attempt a better model I will go ahead and apply colour texture by projecting photographs back onto the surface of the model.

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All material © Kieran Baxter 2012 unless otherwise stated.