Reprocessing the St John the Evangelist data from Gulval

Since first posting about the images of the Four Evangelists found on the medieval cross-base at Gulval Church, I have been striving to produce clearer images of each saint for inclusion in a publication. The image will only ever be as good as the condition of the stone allows, but it is possible to wring a fair amount of detail from the monument through digital means.

The most difficult image of the Evangelists on the Gulval stone is St John. Depicted as half man, half eagle, his side of the cross base is damaged and worn, especially at the top. The details which I would like to further enhance are the eagle head, and the book he is holding in his hand. This is the only side where the lettering is far from clear, and many people remain to be convinced that there is indeed an “IH” (Iohan) carved on it at all.

As many archaeologists do, I have become rather obsessed with this image. When processing data of this nature one does have to be very careful in the interpretation, and not see what one wants to see. Part of my ‘therapy’, if you like, is to blog about the results as I go.

So, I have re-processed the photographs of the east side of the cross-base using the highest level of detail that my computers will allow, adding in some extra angles which I did not use in my initial images, to try and capture further detail at the sculpture’s head level. The processing took from about 7am until 6pm. After some tidying of the data (and a fair amount of quiet wishing that the computer wouldn’t crash), I produced a 1.7GB point cloud ready to inspect.

The use of false colour can be really useful, as it affects one’s perceptions of the data. Good for ‘getting your eye in’ to the data, and the shapes of the carving.

So without further ado, here are some renderings of St John with his Symbol’s head (the eagle). Can you spot any vertical lettering on his book? Fellow digital specialists please note that this is still rough data!

gulval2-east-ambient-occ-1024-128s-bw-hicontrast-ortho-high
High contrast ambient occlusion.
gulval2-east-ambient-occ-1024-128s-ortho-high
Greyscale ambient occlusion.
gulval2-east-ambient-occ-1024-128s-red-yellow-ortho-high
Ambient occlusion using red and yellow colouring
gulval2-east-ambient-occ-1024-128s-redwhite-ortho-high
Ambient occlusion using red and white colouring.

 

A Medieval Discovery at Gulval Church, Cornwall

Gulval Cross-BaseJust to the left of the south porch of Gulval Church, near Penzance in Cornwall, lies a large block of granite. I first came across it on a visit to the churchyard in 2012. However, it really piqued my interest a couple of months ago after reading a short report in Newsletter 132 of the Cornwall Archaeological Society. The article, entitled ‘An unusual stone at Gulval Church‘, by Professor Mick Aston, Teresa Hall, Professor Rosemary Cramp, Ann Preston-Jones and Andrew Langdon, highlighted that the block was a medieval cross-base, and was decorated on all four sides. Aside from the south, pictured here, the images on the other sides were very difficult to see at all. Ann and Andrew visited the stone at night “armed with car batteries, a mirror, two spotlights, a tripod, head torches, and a camera” to capture raking light photos of the decorations to see if controlled shadows could be used to interpret the decorations.

The results were good, producing a set of shadowy atmospheric photos of each side. Professor Cramp began to interpret the scenes from these photos but noted that, while useful, the photos only provided a single fixed view, and she had not seen the cross-base with her own eyes. It was thus difficult to say for sure what was depicted on this rough stone.

It was shortly after receiving the newsletter that I also heard the sad news of Mick Aston’s death. Doubtless that Mick would have had a continued interest in the cross-base, and given that I only live a few miles from the church I became determined to use the tools available to me to record the cross-base and see if I could help with the interpretation.

On 8 June 2013 I visited Gulval Church and recorded in high resolution 3D each side of the cross-base using a photogrammetric approach. Taking a series of over a hundred overlapping 18 megapixel scale photos at a fixed focal length, I covered the whole block.  It was quite a tricky subject to tackle, as there is very limited clearance between the cross-base and two of the church walls.

Over the next few weeks, I began to process the images into 3D point clouds, and from there to solid 3D meshes. Afterwards, I subjected each side to a series of techniques which I have used to analyse prehistoric rock art and inscriptions in the past. The results were fantastic.

What is depicted on the cross-base?

Thanks to this analysis, I believe that we now know what is shown on the cross-base at Gulval. The existing interpretations, as laid out in the CAS Newsletter, didn’t match up with what I have found. The computer-generated images, shown below (and may others that I have created using false colour representations of depth), have been able to provide a slightly clearer representation of the granite carvings, and, I believe, help perceive them in a different way. I can now see many of the details in the original photos now that I know what I am looking for.

Rather than sit on this discovery for ages until everything is just right, I have decided to post my initial findings here. It does not represent a full description of the findings and condition of the cross-base and its imagery, and it builds upon the work already done.

Firstly, I must thank my friend, Nick Ford, for putting me onto the iconography – I believe that he spotted what was depicted in the first image I showed to him straight away, and knew what the others would reveal. It led to an exciting evening searching for comparative images, and further enhancing them. And without the original report in CAS Newsletter 132 (now online) I wouldn’t have got this point at all.

The cross-base depicts the four Evangelists, Matthew, Mark, Luke and John, as the four living creatures described in Ezekiel 10:14 and Rev 4:6-7

Revelation 4:6-7

New International Version (NIV)

6 Also in front of the throne there was what looked like a sea of glass, clear as crystal.

In the center, around the throne, were four living creatures, and they were covered with eyes, in front and in back. 7 The first living creature was like a lion, the second was like an ox, the third had a face like a man, the fourth was like a flying eagle.

The Gulval Four Evangelists

The south side of the stone depicts St Matthew. He is symbolised as a winged man or an angel, and depicted here with a halo, holding a book (Gospels or Book of Life?) with “MT” inscribed on it. The lower part is damaged. This image shows the details picked out using an ambient occlusion filter.

On the west, facing outwards, is St Mark. He is shown kneeling, with haloed lion head. His book, held in his left hand, has “M” on it. It is possible that he is giving the sign of benediction with his right. The folds of his robes are nicely visible.

On the north, facing the church proper, is Luke, depicted here seated with haloed calf head . His book, held in a rather large left hand, has “LS” on it (Lucas). Luke is mainly depicted as an ox, but it isn’t unknown for him to be shown as a calf.

On the east, facing the porch wall, perhaps the most badly eroded of them all, is St John, depicted as the eagle. His robes, especially the folds around his legs, are clearly visible.  It is difficult to discern the presence of any halo. He is holding a book in his right hand, with what looks to be an “H” on it (not easily visible in this image – only range-colouring a very small area shows this). It would be very neat if it said “IH” – Iohan, but archaeology isn’t always a neat discipline. Further work needs to be done here.

We must remember that the stone block onto which these images are carved is a course Lands End granite. Some of the quartz crystals are several centimeters long – fine detail just isn’t possible – and granite can crumble when exposed to the elements.

A Tetramorphic Cross-Base?

So there we have it. Starting on the south side of the stone, if you run the sequence clockwise (South, West, North, East), runs the familiar sequence of Matthew, Mark, Luke and John. Matthew, the best preserved of all, was positioned facing outwards, and the shield-like shape of the carving has, according to some, become thought to be a coat of arms. Now that we know what is really shown here, perhaps we can even call it a tetramorphic cross base, bringing together the symbols of the Four Evangelists together into a single object. One thing is for certain, however, and that is a lot more work needs to be done on the Gulval cross-base, in terms of research, verification, and recording techniques. Reflectance Transformation Imaging (RTI) will certainly be the next approach for further enhancing the panels. Comparative examples need to be sought.

This could have a big impact upon our understanding of Gulval, and indeed have ramifications on how we understand the history of this part of Cornwall in the early Middle Ages.

The authors of the original article in the CAS Newsletter have had copies of the images and my findings in advance of this blog post. Luckily, when I sent my findings to Ann Preston-Jones, she was pleased, as she felt that these were the Evangelists, but lacked firm evidence to back it up. I trust that my arguments, and the images above, will help to win around any doubters.

I have been asked to add the finished images of the Evangelists to the forthcoming Corpus of Early Cornish Sculpture, to which I am honoured to be able to make a contribution. The vicar of Gulval Church is adding the images to his parish newsletter. Who knows, even a sermon may come of it!

Further images and information will be added to subsequent blog posts, and linked from here, so do bookmark this page and check back from time to time.

And now for the plug!

As an independent archaeologist, I am of course pleased to offer my professional services. Please contact me with any enquiries.

Below is a series of images of St John (Eagle) from the east side of the cross-base. The 3D data has been filtered in a number of ways to extract the detail of the carving.

East elevation of a medieval cross base at Gulval, Penzance, depicting St John the Evangelist as an eagle (see Rev 4:6-7 & Ezekiel 10:14). Captured using photogrammetric methods and processed using different filters to interpret the carving.

The Pasties of Penzance

Pasty from Ian Lentern butchers, Penzance
Pasty from Ian Lentern butchers, Penzance
Pasty from Ian Lentern butchers, Penzance

Does Penzance have more pasty shops than anywhere else in Cornwall? The total number of establishments selling fresh hot pasties is now at 20.

When I moved to Penzance one of the first things I had to eat was, of course, a pasty. It was huge. Bigger than my head, and I couldn’t finish it. It was from Lavenders, and made here in the town. After that, I noticed the sheer number of establishments which sold pasties. And there began a most important piece of research. Is Penzance the pasty capital of Cornwall?

Here is a list of establishments that sell fresh, hot (as hot as the Pasty Tax allows, anyway) pasties, baked daily. In the town centre there are 18 19 20 such places. If you know of anywhere that isn’t on the list, tell me. If you know of any other town in Cornwall that has more pasty outlets, I want to know!

Takeaway Pasties

  • Lavenders (Alverton St)
  • Cindy’s (Alverton St)
  • Warrens (Alverton St)
  • AJ’s Eats and Treats (Causewayhead)
  • Rowes (Causewayhead)
  • Mounts Bay Pasty Company (Market Jew St)
  • Warrens (upper Market Jew St)
  • Pellows (Market Jew St)
  • Rowes (Market Jew St)
  • Warrens (lower Market Jew St)
  • Lavenders (Market Jew St)
  • Dreckleys Steakhouse (Wharf Rd)
  • Steamers (Penzance Station)
  • Chy an Clare News (St Clare St, allegedly baked by Lavenders)
  • Costcutters (Market Jew St, sells hot Rowes pasties)
  • Ian Lentern butchers (Chapel St)
  • Cornish Hen deli (Market Place)
  • All Day Takeaway & Ice Cream shop (Barbican & Coinagehall St junction)
  • Barbican Coffee Shop (Barbican Lane)

(19)

Pasties for Eat-in Only

  • Tremenheere Wetherspoons (Market Jew St)

(1)

Pasty and SwanThe best pasties in Penzance?

I’ve had a pasty for my croust (Cornish term for lunch, or just a time when you’re starving) from most of the places listed above. My personal preference is for a large pasty from the Mounts Bay Pasty Company. They’ve got plenty of sweetness and gravy, and the pastry is just right, and nice and buttery, with soft delicious meat. I do like a Lavenders pasty on occasion, but lately they’ve been a bit too salty for me. Warrens is probably the best “mass produced” baker’s pasty in Penzance. They’re actually made in St Just, so it’s still pretty local.

I need your help

Is Penzance truly the pasty capital of Cornwall? Have I missed somewhere? Probably! Leave a comment below and I’ll publish it and add to the list. Does your town have more pasty outlets? Prove it!

Armour Heritage

Armour Heritage
Armour Heritage
Armour Heritage website

My good friend Rob Armour Chelu has recently set up a new archaeology consultancy, Armour Heritage. One of Rob’s many specialisms is archaeological advice for renewable energy schemes whose developments may impact upon the historic environment.

I have set up the bones (if you’ll pardon the appalling pun) of Rob’s archaeology website, and have chosen to use a simple Content Management System (CMS) which enables him to build the rest of the site himself. I am also advising upon Search Engine Optimisation (SEO) and listing on Google Places for Business.

If you need a website, I can help you. Please contact me for further information.

San Pedro de Atacama

20130417-090147.jpg

Here are some fun photos taken on my phone from around San Pedro de Atacama.

The town is built mainly in adobe, which is effectively a mixture of clay-rich soil, straw, and sand. This is often mixed with stones, and walls are then rendered with a clay slip to finish and protect them. Adobe isn’t a material which lends itself to high rise building, so the majority of “SP de Atacama” (as abbreviated on road signs) are single storey.

The town itself is very atmospheric, feeling very much in harmony within its location in a desert oasis. The earthy ochre-coloured mud-built buildings feel like they have been extruded from the ground below, which in a way, they have. Shop signs are wooden, and modern roofs have been topped by reeds to remain in-keeping with the desert town feel. Most restaurants are heated by wood-fired chimineas, found here in their native territory, and totally in-keeping with their terracotta surroundings.

This first photo is a close-up of an adobe wall which has seen better days, to give you an idea of its composition.

(still travelling and posting from my iPhone, so no captions for now – sorryl!)

20130417-084644.jpg

20130417-085933.jpg

20130417-090103.jpg

20130417-090220.jpg

20130417-090235.jpg

20130417-090248.jpg

20130417-090321.jpg

20130417-090332.jpg

20130417-090359.jpg

Adventures in Chile – the journey home

20130416-230111.jpg

Today we landed back in the UK. Thanks to spotty wifi and utterly excusable holiday-induced laziness, I haven’t managed to blog about every place that we visited in Chile, so I will catch up with a few posts this week. Our visit to see flamingos on the great Atacama Salt Flats and the high altitude blue lagoons of Miscanti and Miñique are worth a post each in their own right.

We began travelling back from the Atacama desert on Monday 15th April, at 6.45am. We touched down at Heathrow at about 3pm on Tuesday 16th. Tomorrow, Wednesday 17th, we will make the 6 hour journey back to Penzance. That’s more travelling than I have ever done before, and whilst I loved visiting Chile, I think that a little break from any adventuring afar is in order!

20130416-225734.jpg

We were collected by minibus from our hotel in San Pedro de Atacama, and driven to Calama airport (an hour and a quarter by road) for an internal flight to Santiago at 9.20am. During the journey we watched the sun rise over the Andes, which is always magical. At Santiago we collected our baggage and found our way to the international departures terminal where we checked in to our flight to São Paulo in Brazil at 2.50pm. However, due to some congestion in Argentinian airspace, we didn’t leave until 3.50pm for the four hour flight.

This wasn’t a problem for us, as we had until 11.55pm to wait for our 11 hour connecting flight to London. The air side of São Paulo airport was pretty dismal, with only very limited and expensive options to eat, so we held out by consuming the various packets of snacks which we had collected from other flights. The other annoyance was that security at São Paulo confiscated my water bottle, despite it being bought airside in Santiago, and my compliance with their request to drink some of it in front of them. Just 20 metres away after this little ordeal (which included x-raying my hand luggage 3 times and a full search of it) was the duty free shop, selling all manner of highly alcoholic beverages. I am not sure what their problem was given it was just water. Experiences like this can put people off travelling by air, which is a shame.

There – that’s off my chest! Tonight we are staying at our London basecamp (read: Tehmina’s parents house) and early in the morning it’s back home to our dear Penzance.

Chile is an amazing country in every way. So beautiful, such diversity, genuinely wonderful people, great architecture (Spanish colonial through to adobe churches, to modern glass and steel museums), all framed by the watchful presence of the Andes. Will I go back? Without a doubt. Will I learn a bit more Spanish next time? Absolutemente! I have Tehmina to thank for her talents in picking up a new language as she goes, and having the confidence to make mistakes and learn from them whilst I cower at the back smiling benevolently.

Right, time for some sleep to re-educate my body as to what time, or indeed what day, it is.

Adventures in Chile: The El Taito geysers

I’m typing this sitting in a pleasant 26C heat by a swimming pool. The UV meter outside the (rather excellent) archaeology museum here in San Pedro de Atacama is recommending people of pale complexions to stay out of the sun. Since I currently resemble something akin to a freckled ghost, I’m doing just that. Some quiet blogging time for me then.

A couple of days ago Tehmina and I visited the El Taito geysers, a geyser field located in the Andes at an altitude of about 4300m. Our day began at 5.30am, when we met our guide, Leo, who would make sure that we saw the best of the scenery on the way there and back, and were safe and well-informed during our visit to the geysers.

Here’s a few (unedited) photos to give you a feel for what the El Taito geysers look like. The reason for the visit to be so early is because it is cold (-5C), and the steam clouds are visible as the water vapour (at 85C) cools and condenses. Also, the view of the columns of steam as the sun rises is stunning.

20130416-221001.jpg

20130416-221023.jpg

20130416-221043.jpg

20130416-221108.jpg

The geysers only shoot water to a height of about 75cm on average, but the alien feel to the place, with its organic shaped mineral deposits, columns of steam, and the gulping, belching sound made by the water pressure make this a fascinating place to visit. The air is quite thin at this altitude, so we were recommended to walk slowly by our guide, especially as it is so cold. Visitors must also not cross the stone markers, as the ground is rather unstable. Putting your foot in a puddle is one thing, but quite another if said water is close to boiling point…

We breakfasted by the geysers, then headed back down the mountains to the village of Machupa, a tiny adobe and stone village which sadly seems geared up as a tourist photo attraction, but is still worth a visit if you are interested in traditional building construction of the area.

20130416-222418.jpg

20130416-222454.jpg

20130416-222514.jpg

It was still too early in the morning for me to sample a llama kebab, so we waited in the van whilst our brave tour companions ate theirs. We then continued down to a river to have a look at some local birds, and caught our first glimpse of a couple of flamingos, and some coots, amongst others.

20130416-222814.jpg

Then it was back to San Pedro de Atacama to have a rest and explore the town some more. And maybe seek out a Pisco sour or two.

Adventures in Chile – Valle de la Luna

Imagine a landscape that is so barren, so alien, yet beautiful in its many forms. Shiny rock salt crystals glint and shine as the sun lowers in the sky. Small cave systems, organically shaped by water millennia ago, meander through gorges. This is Valle de la Luna, or Moon Valley, situated in the north of the salt flats in the Atacama desert, Chile.

We were taken there by our guide, who helped to show us the best of the valley, and led us, often on hands and knees, through a cave unlike any other I have seen. We finished our day watching the sun set, and the terribly beautiful colour changes that happen, whilst drinking wine and eating cheese. I will never forget that evening.

Here are a few of the many photos I took. Please excuse the lack of captions for now – the mobile WordPress app doesn’t support them yet, and as I’m on holiday I’m not going to hard-code them!

20130414-161631.jpg

20130414-161710.jpg

20130414-161753.jpg

20130414-161833.jpg

20130414-161854.jpg

20130414-161918.jpg

20130414-161943.jpg

20130414-161957.jpg

20130414-162014.jpg

20130414-162044.jpg

20130414-162115.jpg

20130414-162139.jpg

20130414-162151.jpg

20130414-162214.jpg