Working on The Wall

One of the advantages of being on an archaeological site during its excavation season is the ability to make 3D models of structures at different phases of excavation. During the course of excavation at the Ness of Brodgar, I will be recording the excavation of the curving, northern wall in structure 1, creating 3D models of the wall as it is removed. Sketch plan drawings are created during the course of the removal of a structure such as this, usually after each layer or phase of the structure has been removed, however creating a 3D model of the structure at these intervals can add an extra level of detail for the archaeological record. Indeed, one can view the wall as it was at a certain period of excavation and compare this with the plans which are normally sketched, to aid in interpretation.

“one could be under the impression that

creating the 3D model in sunshine would add

an extra, brighter level of detail,

however there are issues with this”

 

There are potential problems which need to be avoided when creating a model of a structure such as this. The first issue is the sun, one could be under the impression that creating the 3D model in sunshine would add an extra, brighter level of detail, however there are issues with this. Shadows can be problematic during any photographic work when recording archaeology, as they can hide details which would be visible in a more over-cast environment. Moreover, they can give an inaccurate perspective of a structure or trench when photographed at certain angles. This is often an unavoidable problem when recording on an excavation. However, this is only one issue caused by shadows when creating 3D models. Shadows can also potentially confuse the 3D modelling software when taking multiple images. If the sun is hiding behind clouds when I start the photogrammetry process, and then comes out halfway through, I have a model where half the model has shadows and the other half is overcast. The modelling software may then have trouble identifying the area as one structure and model.

Another issue can be the rain, if it had been raining and there are small puddles in the area to be recorded, the reflective surface of the water can also cause problems for the software. These issues can be overcome by either removing the puddles with sponges or removed from the model digitally, however this is far from ideal. Finally, if it is very windy and there are objects in the structure that are moving about, the software will again be confused by the movement and won’t be able to align the photographs in order to create a point cloud, or at the least will create a blurry, poor quality model. I’ll describe this process of point cloud creation in more detail in another blog, but as far as the process of taking all the photographs is concerned, all these issues are best avoided if possible. The perfect ‘Goldilocks’ conditions for a nice 3D model of a structure such as the wall, are overcast, when it hasn’t been recently raining and it is not too windy, conditions that are can be often hard to capture when working in Orkney, so there are always new skills to be learned in order to work around these issues.

For a view of the 3D model of the wall in structure 1, taken before layers have begun to be removed, see below.

 

You can find out more about The Ness of Brodgar, along with the work undertaken on the wall in structure 1, in the Ness of Brodgar People, Place and Perception videos, by Simon Gray here: http://www.nessofbrodgar.co.uk/dig-diary/video-diary/

The Cairns Project Collection

Here you can see a collection of 3D models I have made over the season at the Cairns Project in South Ronaldsay so far. Many more will be added over time. *Caution* some of the models may take a long time to load or may not load at all on slower devices or PCs. I will soon be making lighter versions of some of the very detailed models for viewing on all devices.

Recording a site over time

One of the first things I wanted to do when arriving at the Cairns site, just after it had been uncovered, was to record as much as I could for photogrammetry in the early phases of the excavation season. There were two reasons for this, the first was to make sure that the photographs taken were of adequate quality, that I was taking shots in the correct positions and that camera settings were all correctly prepared for site recording. If the software didn’t work with my photographs, I could iron out any problems early on. The second reason was so that I could get models of the site before excavation started, then as the season progressed, I could create other models of the same areas to compare with the models created earlier, thus building up a record of the excavation season and the changes to the site over time. The model below is of Trench M at The Cairns, just after it had been uncovered for the 2017 season. The gaps in the trench model are caused by an unavoidable problem with the photogrammetry software..the bugbear of any digital archaeologist attempting photogrammetry.. water ! Anything reflective causes problems when making models, but I’ll save that for another blog !

Digital archaeology at the Cairns and Ness of Brodgar

Over the excavation seasons at The Cairns Project and the Ness of Brodgar, I’ll be spending time as the ‘on-site digital archaeologist’. That may sound like an unusual term and one of the reasons for this is that, put simply, it is an unusual thing to do.

Quite often, digital work undertaken for archaeological excavations is completed after the dig season has finished. 3D models of finds created using photogrammetry are usually made in the comfort of a warm office or lab after the finds have been categorised, labelled and wrapped up for preservation, or put on display in a museum. 3D models of trenches during an excavation season are sometimes made, however usually this is just a single model of a particular context during excavation.

Being on the excavation site for the entirety of the dig at The Cairns and Ness of Brodgar, enables the opportunity to generate some 3D models of the same trench at different phases, when different contexts are being discovered. Moreover, when a particularly interesting find is discovered, I can be there to make a 3D model just as it’s unearthed. That way, we can get some 3D models out there for everyone to view the day they are found. Recently, I made the model below of what has been termed the ‘Red Cell’. The Red Cell is a small compartment or room, just off from the centre of the broch.

I’ll be posting more models over the season which I will include in future blogs. Some models may appear on the Friends of the Cairns Facebook page and the @thecairnsbroch Twitter page, on www.nessofbrodgar.co.uk, along with the @UHIArchaeology Twitter page, all great sources for information about the Cairns and Ness projects.

I will also be trying out some interesting new techniques for photogrammetry, utilising different software packages and trying out some experimental digital archaeology, so there will be a lot to see and a lot to write about.