I enjoyed seeing the article in last Saturday’s paper about using the remote images from aerial and mapping techniques to investigate archeological sites – techniques like Google Earth, LIDAR and old maps. (Ref. 1) The images from these methods have existed for a while but are now being combined in new ways. I’ve used the images separately in the forensic investigation of failures and accidents in the built environment.
The article is a good, informative, almost jargon-free read that might herald what’s coming in forensic investigation.
The difference today is that an archeologist, Dr. Jonathan Fowler, Saint Mary’s University, Halifax is using software to combine the remote images from different methods to get a 3D view and even more data from a site. Data “pops out at you” to use Dr. Fowler’s expression. The software is produced by Golden Software in Colorado.
Example of Dr. Fowler’s work
A good example in the article of Jonathan’s work is certain to interest you. It shows different remote images of historic Fort Anne and Fortress Louisbourg in Nova Scotia.
The images are remote because they’re from cameras and sensing devices that are high above a site – a little like the images from video cameras mounted on drones that are flying low over a site.
Jonathan’s recent work has been made possible by the Nova Scotia government releasing in 2020 great volumes of free LIDAR data; “…it just felt like Christmas to me.” (Ref. 1) The data is available to the man-in-the-street for most of Nova Scotia.
Examples of forensic work using remote images
#1 I had that festive feeling when the government gave me LIDAR imagery for the site of a swimming pool failure in Cape Breton several years ago. I was investigating the reason one end of the swimming pool was several inches lower than the other. You could see the difference in the distance from the pool deck to the water’s surface. The cause popped out from the imagery: The swimming pool was built on filled ground over a bog – compressible foundation soils in the extreme.
#2 A few months ago Google Earth imagery enabled me to virtually visually assess the cause of a retaining wall failure in Ottawa and contribute to a big reduction in the cost of the wall’s rebuilding.
#3 Free software that relies on Google Earth imagery enables me to plan video of the site of a failure or accident from a virtual drone flight over the site days before and hours of driving away. This has been a godsend for me in my forensic work – a more effective investigation at lower cost.
#4 In the past we used what are old maps today: Large scale, contoured, topographic maps of built up areas made from aerial photographs taken from planes flying at 6,000 feet. They can be quite detailed and accurate. We would be remiss not to refer to them today, and couple them with Google Earth and LIDAR imagery like Jonathan is doing. Even older maps exist today of sites like Fort Anne and Fortress Louisbourg.
#5 I’ve also used stereo pairs of aerial photographs to assess the terrain at a forensic site – terrain analysis in engineering. Details of micro-topography revealed in an analysis often give evidence of features below the surface. (Ref. 1) It was a standard technique in an Australian firm where I worked when selecting a route for a highway in a remote area of Indonesia.
It just keeps getting better what archeologists and forensic engineers can get today from remote imagery and suitable software.
Still, ground proofing is needed – getting your hands dirty and mud on your boots walking around on the site. This to confirm what you thought you saw in the pictures and images from above. It’s an old technique and a hard and fast rule in engineering, as I’m certain too in archeology.
(LIDAR, or Light Detection and Ranging, uses pulsed laser to measure the earth’s surface)
- Archeologist Lauds Advances in Mapping, Peddle, Stuart, The Chronicle Herald, Halifax March 27, 2021
(Posted by Eric E. Jorden, M.Sc., P.Eng. Consulting Professional Engineer, Forensic Engineer, Geotechnology Ltd., Halifax, Nova Scotia, Canada, March 31, 2021 email@example.com)