Ham Hill Iron Age Skeletons Turn Digital


Three of the skeletons found at the site of Ham Hill, Somerset during the 2013 excavation are now available to view online at the following links:




The skeletons were discovered during this year’s excavation carried out by the Cambridge Archaeological Unit and Cardiff University, at the site of an important Iron Age hill fort. They are only some of the many human remains found, some of which were carefully placed within a number of pits, while others were located symbolically within an enclosure ditch, often with body parts missing.


The models themselves were made using Photogrammetry and specifically 123D Catch, which required very little time for quite good quality. The aim of this was to preserve a record of the skeletons in situ for further interpretation once they had been removed from the location they were discovered in.

Given the complexity of the subject, the results seem to be very promising. Time was a big factor when making the models, as they had to be removed before damage occurred. Some of them were also in tight spots, which made it hard to access some of the standard angles, but overall this was counterbalanced by taking a larger number of photographs than normally (around 30 per skeleton). The lighting conditions also proved to be ideal, as there was an overcast sky, but also sufficient sunlight coming through to really emphasise the surfaces.


For further information on the skeletons I suggest reading the article at http://www.bbc.co.uk/news/uk-england-somerset-23928612


Glastonbury Ware Pot – Ham Hill

This is one of the first attempts I made with Photogrammetry, and probably one of the ones I am most happy with. It is a beautiful pot found during the 2011 excavation, and that was glued together to show how it would have been prior to destruction. I made the model using around 60 images with 123D Catch, and good natural lighting that brought out the contrasts well, especially with regards to the decoration.
The thing I am extremely happy with is that I was able to create both sides, something which I was struggling to do before, and which was probably helped with the large number of images.
The animation itself was made using the tool in 123D Catch, which is ideal to display the model, although it is hard to create a non-wavy video, as this one shows. Still, in absence of suitable programs, or updated browsers for Sketchfab, it is an ideal tool, as it can be uploaded to youtube and shared with anyone interested.
As an addition though the model can also be viewed at the following link: https://sketchfab.com/show/8ABDov7xS8kV8mfbGMuQkFOmjE3


Modelling Large Scale Features with 123D Catch


In the previous entries we have seen the use of Photogrammetry in archaeology for the recording of features and artefacts. With models of this kind the procedure is pretty simple: you take 20 or so photos from different angles and then run them through 123D Catch to get the end result. The angles themselves generally should be every 45 degrees in a circle around the object and the same from a different hight, but because of the small scale there is quite a bit of leave way on precision of these positions.

The same cannot be said when dealing with a larger feature or an entire site, which for Photogrammetry generally refers to anything larger than 2 metres or so. In these cases it not only a question of angles and of how precise these angles are, it is also a question of making sure that every single point of the surface is recorded on at least three photographs. In smaller stuff this happens easily, as each photograph contains nearly the entirety of the feature. But on larger features the only way to achieve this is to take the images from a distance, which reduces the quality.

Many tests I have conducted have suggested that the best way to achieve a large scale model is to photograph the first spiral around the feature at a distance, in order to set the basis for the model, and then at a closer angle to  get the detail. This will increase the number of photographs needed, so the trick is to find a balance between the number of photographs and the need to photograph all points.


If the model still has missing data the other approach is manual stitching. Manual stitching can be easy and straightforward or complex and problematic, so sometimes it is just easier to take the images again. If this is not possible 123D Catch does allow to glue unstiched photos together, and even to look through the photos that are already stitched to see if any mistakes have been made (this has saved me a number of times).

The main thing with large features is to try many different approaches until one works. Persistence as usual is key for great models.

Here are some examples: