Jarlshof December Site Visit

This photo taken by Kieran Duncan © 2011 shows me taking pole aerial photography sequences at Jarlshof near Sumburgh Head, Shetland. Although we were only on the island for three days the weather was kind and allowed for extensive photography to hopefully use for photogrammetry later. The close proximity of Sumburgh airport to Jarlshof restricts kite flying although my hope is that pole aerial photography will be suitable for capturing most of the site.



The winter conditions were visually pleasing in many ways with a dusting of snow bringing out the topography of the Norse part of the settlement (below, right). The benefits of an elevated view are immediately obvious at this site where features such as the curve of the broch wall (below, left), obscured by later structures and erosion, are difficult to make out on the ground.



A very satisfying first visit to the site which has left me with around 13,000 frames to work with towards digital reconstruction. Enough to keep me busy until my next visit!

Best wishes for the winter solstice and 2012!

Shell Photogrammetry Sub-Millimeter Test

This shell measures 27mm long and was processed into the 3D model below using macro photography and photogrammetry. This loop fades between true colour combined with artificial light, then grey topography and back again.



I was careful to light the surface in such a way that the shadow of the camera would be clear for all of the positions needed. The shell was supported with a pin and bluetac, visible at the base. This test was designed to explore the potential of these techniques for recording archaeological artifacts.

PAP and Photogrammetry Test at Ardestie

This test was derived from a series of pole aerial photographs. It shows the original colour projection, the topography under rendered lighting, and the two combined to artificially light the scene. Although not as polished as the Tealing test this was an experiment in the use of PAP for photogrammetry.

Jarlshof - Impressions of a 4000 Year History

I am working on this series of drawings and photo-montages in order to plan out angles of view as well as to study the colours and atmospheres which I will be looking to create in the digital reconstruction. These may also serve as a starting point for further archaeological consultation, I suspect that many of the details here will turn out to be woefully inaccurate.



Drawing is a good way to study the site and in this case I am increasingly aware of complexity of the chronology at Jarlshof, with buildings from different eras often built on top of one another.

Hut Circle Topography at Bridge of Cally

"...traces of the others [hut circles] are very slight and were only recorded by oblique sunlight at about 1pm on a winters afternoon..." (RCAHMS, 1987)

This description prefaces the site record of Rochallie at Bridge of Cally which features two groups of hut circles among cairns and other features. The practice of waiting for snow and low light in order to see the topography of an un-excavated site is still widespread. With this in mind I set out to replicate the effect described at Rochallie using KAP and photogrammetry.



This first image is an orthographic colour projection derived from two KAP sequences. It is annotated with my interpretation of the hut circles and features based on the RCAHMS report and my own observation.



This second image is derived from the same data but with the colour removed and lit from a series of low angle lights. The three main hut circles can be seen in the center along with the other features. The photographs below give an idea of how difficult it is to perceive the topography in normal conditions, the more distinct hut circles and cairns are visible only on close inspection.



Hopefully these images demonstrate a fairly successful test of photogrammtery as a method for recording an obscured site. With hindsight I would attempt to capture the entire area in one pass for better coverage rather than going for multiple angles of such a low lying site. Although I was concerned that the software (123D Catch) would have issues with the similar grass texture this was no problem. Instead the main issue was recognizing the continuity from one frame to the next, something to consider when capturing in future.

Tealing Souterrain & Roundhouse Interpretation

A composite showing how the wooden roundhouse may have related to the excavated cellar at Tealing. This shot is made up of photogrammetry based on KAP at both Tealing and the Scottish Crannog Centre.

This has served as an important test of principles and brought up some of the concerns I can expect to face taking photogrammetry data to a final composite. In future more of an effort will be needed to keep render time down with basic efficiencies such as combining three lights onto the channels of one layer. I think that raytracing features such as shadows and ambient occlusion will only be possible if they are baked onto the surface- which shouldn't be a problem in these static environments.

I chose to orientate the crannog roof to keep the door to the sheltered north east. On reflection it would have been better to create a new door (the existing one was exaggerated from the original data anyway) in order to keep the patches of lichen on the damp northern side.

The internal structure is deliberately revealed using 2D transitions as I felt that rising the structure in 3D would in no way represent the process by which it was built. I think I would prefer the reveal to look manipulated than be misleading.

Near Infrared Photography at Laws of Monifieth

I was recently lucky enough to meet three kite photographers from the West Lothian Archaeology Group, John and Rosie Wells along with Jim Knowles, who delivered a lecture at RCAHMS advocating the use of low altitude aerial photography for archaeology.

Among many great examples of applications were aerial views which have been used to establish potential sites. Often buried features show up in crop growth with parch marks assotiated with disruptions in the soil. Healthy plants reflect infrared light so these parch marks can sometimes be observed by near infrared photography before they are visible to the naked eye.

As it happens digital camera sensors are highly sensitive to infrared light so any camera can be converted to capture these wavelengths by replacing an internal filter. John Wells very kindly lent me a converted Pentax Optio E35 capable of photographing wavelengths of 720nm. The results of my first experiments with infrared images at Laws fort and broch site near Monifieth are shown hear alongside standard visible light views.




It is clear why the site would make a good broch location with views for many miles across Angus and Fife. Tentsmuir beach is in the background of the fort in the visible light version. Notice out of the two fields in the background the darker but greener vegetation shows up brightest in the infrared




These photographs taken from a pole show the possible broch site which measures around 20m diameter. There isn't very much here in way of features showing through the vegetation although the snowy looking grass in the infrared removes some of the surface texture helping make out the topography. I find these unusual images visually striking as well as interesting to analyze and look forward to trying this out at different sites.

Alan Sorrel - How Traditional Interpretative Illustration Can Relate to Digital Visualisation

A landmark figure in archaeological interpretation, Alan Sorrel (1904 – 1974) produced many well cirulated paintings and drawings depicting British historical sites reconstructed. Of particular interest to my project are two illustrations of Jarshof, one depicting the iron age broch and village, one showing the later Norse settlements with the ruined broch just visible in the background.

Sorrel's illustrations are striking not just for their attention to detail but also for their consideration of mood and atmosphere. It is perhaps this sense of drama which has seen his work cited as a source of inspiration for both archaeologists and laypersons to the field. He gives the impression of a living site, a feeling I would like to instill in my own work.

It is clear that the reconstructed details are informed by the best opinions of archaeologists of the time. For example his drawing of Clickhimin Broch shows the 'lean-to' roof structure as interpreted by John Hammilton who excavated the site, along with Jarshof, in the early 1950's. Opinions change however and it is now considered more likely that the broch roof structures where more in line with roundhouse traditions (Armit, 2003).

Sorrel's reconstruction of Jarshof broch seems to be modeled fairly closely on the completed specimen of Mousa, a similar approach to the superimposition I intend to use for my interpretive film.

Another striking similarity to the kind of work I have been looking at is the angle of view. Although a spatial analysis would be fruitless in such a drawing, if we assume the broch is based on the 13m Mousa then the position of the horizon would put the 'camera' at around 15m height above ground. This is a low altitude aerial angle, only achievable in photography by kite, balloon etc.

In sorrel's work this is the rule and not the exception. Almost all of his reconstruction illustrations are made from low altitude aerial angles - high enough to lay out the site and expose the overall shape of it's components while low enough to retain a wide angle perspective and a sense of intimacy with the figures in the scene.

This parallel is encouraging for my own work and raises questions of how Sorrel derived these views, what reference he used and how much was down to imagination. These questions I intend to put to the Alan Sorrel Research Project, a collective who are studying his work and the memories of those who knew him.

Citation:
Armit, I., Towers in the North, 2003, Gloucestershire: The History Press.

Pole Aerial Photography at Ardestie Earth House

I chose this low lying site to try photographing with an eight meter pole, made with three window cleaning kits stacked together. In fact I started out with nine meters but quickly bent one of the sections by supporting it too low down. With more support a little higher up I was able to confidently position the camera above the site.



This Earth House is similar to the one which I photographed at nearby Tealing with the addition of three huts, the foundations of which remain in a row with one leading off into the curved cellar. A drain is also visible runing along the center of the earth house.



I hope that images captured in this way will be well suited for photogrammetry and will try processing this sequence at a later date. The advantages of PAP over KAP include an ease of use for capturing details, no reliance on wind conditions, and an alternative where kite flying may be impossible due to surrounding power lines, airports etc. For this reason it will be important to pursue as a backup if CAA permissions at Jarshof prove to be impossible.

The Dugout Canoe - Photogrammetry of a 1,500 Year Old Artifact

This ancient boat was lifted from the river Tay where it lay preserved for around 1,500 years. It is likely that dugout canoes such as this one where used to travel at least as far as between Dundee and the Loch Tay crannogs via the river Tay.

This example is on display in McManus Galleries where I photographed it from different angles and along it's full length. It's surroundings made it only possible to capture one side hence the dark holes which represent lack of data. I uploaded 100 photographs to Autodesk 123D Catch (formerly Autodesk Photofly) which returned a model of 16,000 vertices.



I have tried to light it in such a way as to bring out the relief detail of the wood as well as highlight the flat bottom of the vessel.

Terrain, Territory and Tentsmuir KAP

When thinking about how ancient sites would have looked from the air we can consider that the surrounding context may have been more unrecognizable than the site itself. Modern farming methods leave a graphic impression on the land, often a patchwork of straight and parallel lines which make it hard to visualize a site as it's first inhabitants may have found it.

It will be important in my reconstruction project not just to look at sources of untouched land but to think about the impressions which early settlers would have left on their surroundings. In communities who spent a lot of their time living and working outside we can assume that the unused land around ancient settlements would have been a web of paths, well worn by people and animals.



I took these kite photographs yesterday at Tentsmuir National Nature Reserve, a site largely undeveloped by human forces although it's many visitors have traced a network of paths in the dunes and flat land behind the beach. While exploring the landscape these visitors have caused a transformation reminiscent of what William Fox describes as "...converting land into landscape, or terrain into territory" (Fox, 2009). I found this a strong description of how our regard for a particular area can make a clear impression on the land as well as on the people who have interacted with it.

A fascinating aspect of Jarshof in Shetland is that people have been drawn to settle on the same site for over 4000 years. For whatever strategic advantage the location had it has been firmly claimed as territory time and time again. By reconstructing these changes using aerial perspectives I hope to enable the modern day visitor to build a familiarity of the site and ultimately their own claim to territory.



The dangers of using new media to present real history to an audience can be summed up by the arguments of the French theorist Jean Baudrillard. In fitting with the subject Baudrillard used the analogy of a map, or simulation, which is meant to represent a terrain, or reality (Baudrillard, 1994). The danger is that the "map" can become departed from the real, and while the audience accepts the simulation the reality can become obscured.

Interpretive reconstruction, while perhaps a contradiction of terms, is at the very least surrounded by issues of integrity. While it is tempting to use whatever imagery will instill a strong atmosphere in my film, it is a little pointless if not representational of the evidence and facts which have been established around the site.



While these photographs of Tentsmuir might provide a visually strong part of a backdrop to the bronze age settlement, it will be important to study the forces at work at the current day site as well as what can be interpolated about both geological terrain, and human territory, in the time of these ancient settlers.


References:

Baudrillard, J., 1994, Simulacra and Simulation, Michigan: The University of Michigan Press.

Fox, W., 2009, Aereality, Berkley: Counterpoint.

The Crannog by Night

A very pleasant evening of storytelling and music at The Scottish Crannog Centre. I was interested to see how smoke from the fire seeped through the closed thatch roof. This is visible in the two 30 second exposures of the exterior.

Reconstructing the Crannog Roof from KAP to 3D

I selected 114 photographs of the Crannog from different angles to generate a point cloud of 84,000 vertices. This was cleaned a little and then poisson surface reconstruction applied to generate this mesh:



The spatial accuracy of this geometry makes it easy to texture by projecting the original photographs onto the surface. This turnaround was textured using just one straight-down frame:



There are more photograhs, and therefore data acuarcy, on one side than the other. Of the more subtle features which have survived in the photogrammetry data you can make out the archway above the door and verticle ridges which relate to the suporting structure underneath the thatch.

Photographing the Iron Age Roof at Loch Tay's Crannog

The Scottish Crannog Centre is a reconstruction of a 2600 year old roundhouse built out on the waters of Loch Tay. It is of particular interest to my project as the roof is of a similar structure to what may have covered the northern brochs.



My aim was to capture the detail of the roof in different lighting conditions and from enough angles to attempt photogrammetry. Because of the surrounding trees and water I flew the kite from a small boat, skillfully piloted by my brother Dan. After several passes, 2 hours and over 4000 frames we got the angles I was looking for.



The Crannog was built in 1994 based on underwater excavations of Oakbank, a site further along the loch. For the most part traditional methods and materials were used in the reconstruction although it is worth mentioning that the original roof was most likely thatched with bracken rather than the reed thatch used in the contemporary version. The bracken would probably have appeared rougher and darker and would have decomposed faster. The spread of lichen (white dots) on the shaded north side is clearly visible after just over 15 years.



Taking a tour of the Crannog you can get a feel for the life and atmosphere in this kind of settlement. There is no chimney, instead smoke would filter slowly through the roof, helping to preserve meat which would be hung there. A short video and history of the Crannog can be found here.

Climate Averages for Shetland & Orkney

This data derived from the Met Office website shows monthly averages up to the year 2000. I have divided the hours of sunlight by the hours of daylight to get a percentage likelyhood that at any given moment during the day the sun will be out. Throughout the year Shetland looks to expect around 2.5% less sun than Orkney as well as more rain and slightly stronger wind during the winter. The yearly cycle looks much the same between locations and these trends should help me to plan trips to capture the kite photographs I will need.

Possible Project Locations

For my MSc visualisation project I aim to make short film using aerial reconstruction to tell the story of a historical site.


View Jarshof on a Larger Map

Jarshof is my first choice. The site dates from 2,500 BC and is layered with a complex chronology including Bronze Age houses, an Iron Age broch and a Viking settlement among more recent structures. The Iron age portion has been dramatically eroded by the sea and it was here where the site was uncovered after storm erosion in the late 1800s. The stories surrounding the site make it an attractive choice to base my film around.

Zoom out a little on the map and you will notice that Jarlshof lies around 300m from the end of the runway at Sumburgh Head airport, making it effectively a no fly zone for kites.

Problem. I'm pursuing the possibility of CAA permission to fly kites at the site as well a pole photography and other low level photography options. Failing this I can go for my second option:


View Gurness on a Larger Map

Gurness is a 2000 year old ruined broch village site. The exposed remains of the walls and outer ditches could be well illustrated from above.

The benefit of using broch sites is that with over 500 known sites across Scotland there is the opportunity to synthesize photographs and geometry from a complete broch to aid the re-construction of a ruined site.

St Bridget's Kirk Commission

This kite photograph was commissioned by Historic Scotland for a new interpretation panel on the Fife Coastal Path which runs behind the church in Dalgety Bay. The brief was to illustrate the coastline's proximity to the graveyard, a connection which is important to the kirk's history. A difficult location with trees and tides to deal with but a pleasing result. I have passed on ownership of the image and it is reproduced here by kind permission of Historic Scotland © 2011.

Tealing Earthhouse

This 2000 year old storage cellar would have been part of a larger roundhouse built above ground. Situated in Tealing just outside of Dundee it presents the same challenges for KAP and photogrammetry which I expect to face capturing other Iron Age ruins, the biggest being overhanging walls. I shot around 2000 frames this evening which I'll attempt to resolve into 3D at a later date. Details of the site here.

Aerial Inspiration

The film 'Home', among other work by Yann Arthus-Bertrand, is a great example of where aerial perspectives can bring a sense of reflection and global unity to an audience. His images are both illustrative and emotive relating human interactions with a landscape which is often vast and alien looking from above.

There is a strong element of simple truth-telling in his work which gives it some extent of universal appeal. Despite this his later work has become increasingly politically strategical. He is a vocal ecological activist and founded the umbrella organisation GoodPlanet.org which is concerned with climate change issues and the protection of biodiversity.

Home was released for free and can be streamed here.

Photogrammetry tests

Some experiments with photogrammetry software using a sequence of 33 kite photographs of Callanish Standing Stones, taken back in 2007.



This is a Maya render of geometry generated by Arc3D. It took around an hour to resolve on their servers. It has missed a couple of the thinner standing stones but overall I'm impressed by the detail, particularly on the ground and the ruined burial chamber in the center.



Photosynth turned the same image sequence into this cloud of around 50,000 points. These results look more thorough but will require a tool to convert the points into a mesh for Maya.



Perhaps the best results from Autodesk Photofly with mesh generation (this one is only draft quality) and the very nice faeture that it projects the photographs onto the UV map automatically. Next to run it on a fast enough windows PC to generate a high quality mesh. These three images are Maya renders of the Photofly mesh.

New Kite & Camera Rig

Just purchased a new Fled kite- a sparred version of a sled. At 1.5 x 2 meters across the hope is that I'll no longer be frustrated by very light winds, a quick test demonstrated enormous lifting power. That's it below on the right.

Another recent addition to my KAP kit is a Brooxes Simplex rig, compatible with my Panasonic LX3. This is the first time I have bought a rig rather than built one. Although I found it very well made, with some ingenious features such as Kaphooks for attaching to the line, it is still heavier and more bulky than my own rig. When I have the time to develop handmade rigs is a lot of fun and perhaps worthwhile too.

The photograph below of Dundee's Law Monument was taken on the first flight of my LX3. Although until now I have used Canon Powershots, this camera's 25mm equivalent lens makes for very pleasing results.

Investigating KAP and Photogrammetry

I have been building a portfolio of Kite Aerial Photographs, using a handmade auto KAP rig and a compact camera, since 2007. As part of my MSc Animation & Visualisation I am looking at ways of using these still images to generate 3D environments for historical visualisation.

Photogrammetry is the process of comparing features in a number of photographs of the same subject from different angles, and resolves them into 3D space. A number of software solutions for photogrammetry applications are discussed here.

This method of recording geometric data suffers in reliability compared to laser scanning techniques as it depends upon surface texture and lighting conditions. It also relies on adequate parallax between the images used (making it suitable for KAP where there is often plenty of lateral movement).

Photogrammetry has the advantage of being able to be captured with low cost lightweight cameras which can be used where a scanner might not be able to reach and at any scale.

The Discovery Program (an Irish institute for archaeological research) has used Photogrammerty from a Helikite in conjunction with terrestrial laser scanning to recreate historical sites, see article here.

Greg Downing has also used a combination of KAP and photogrammetry to document an archaeological site in Egypt, where obtaining permission to fly an aircraft for photography proved too difficult. He used an auto KAP rig to capture around 300 images, resolved into this 3D point cloud.

I continue to search for for a historical site which would be well suited to KAP and Photogrammetry techniques, as well as having a strong story which the resulting animation can be orientated around.

Photos from the third annual Digital Documentation conference in Glasgow. The conference focused on laser scanning and other documentation techniques for heritage sites, featuring the Scottish Ten Project among many other guest speakers.