UAV Infrared Mapping of Archaeological Sites in Greece

Methods

Summary

Before any flying will occur on site, several key areas of invesigation will be cleared of grass. This will allow any thermal signature from underground remains to be picked up.

I will then place a series of metal crosses around the site. These crosses will act as ground control points, which will be located spacially using a Differential GPS. This will allow any photographs/3D models etc to be georectified.

Each area of investigation will be flown three times in each session. Several transects of the area will be flown at a height ranging from 10/20m above ground level with a normal camera continuously shooting every 3 seconds in order to create an orthophotograph using Agisoft Photoscan. This will act as a control so we can see any marks on the ground that may cause a thermal variation.  The same area will then be flown twice at 15-20m above ground level with the Thermal Camera, which will be set to take photographs every 2 seconds. These flights will occur at lots of different times of the day including before dusk and after dawn.

For any further information on the topic of digital recording, check out my two articles:

Thomas, H. (2016). ‘Quantitative analysis of two low cost aerial photography platforms: A case study of the Geometric site of Zagora, Greece.’ The Journal of Field Archaeology. doi: 10.1080/00934690.2016.1208551

Thomas, H. & Kennedy, M. A. (2016). ‘A New Methodology for Digital Planning of Archaeological sites without the aid of Surveying Equipment.’ The Journal of Archaeological Science: Reports. doi: 10.1016/j.jasrep.2016.06.006

Challenges

I have worked at Zagora during 2012-2014 as both an excavator, surveyor and digital recorder. In all, I would have spent over 100 days, trudging around the site. As such, I know about the challenges of Zagora.

The biggest challenge on the site is the evironmental conditions. Zagora is famous for the Cycladic winds that buffet the site. The video shows a common day with wind blowing at 80km/h. As such, I will have to rely a lot on weather forecasts and plan specific tasks accordingly. I need to make sure that with days of optimal conditions, that I spend the entire day taking photographs.

The other issue is the remoteness of the site. To get to the site is a 2km walk along rough, rocky paths. On the return leg, the walk ascends some 100+ meters, which is the equivalent to 33 stories! As such, getting equipment into the site is tough. 

Pre Analysis Plan

There are several different forms of data produced by this project. The first is normal photographs. I will take somewhere in the region of 2000-4000 photographs of Zagora, which I will then turn into a 3D model using software called Agisoft Photoscan. This can take days of computer processing.

The thermal imagery will be turned into its own 3D model, or if that fails, a photomosaic. Analysis of these photographs is time consuming. I will analyse small 50mx50m sections of the site using Adobe Photoshop. I will edit the colour settings, trying to isolate and ephasise any thermal hotspots that appear. I will then compare these against the 3D model produced with the normal photographs in order to see if their is any natural reason for the thermal differentiation.

Once that has been ruled out, a report will be submitted to the AAIA and University of Sydney, detailing all the findings and possible interpretations. This will then be modified into an academic article to be published in a scientific journal.