I continue to be impressed by how valuable aerial photographs are in forensic engineering investigation. Most recently by the high resolution of photographs of urban areas from Google Earth Pro. You’ll be impressed too when you get photographs from Google Earth of a site involved in a civil case or insurance claim, possibly even before you retain an expert.

However, the resolution is not so good of rural areas. You get a big picture but it has a blurry look when you zoom in low. It’s not so suitable for reliable terrain analysis and data collection.

I tested this a few days ago by comparing Google Earth resolution to that on video from a drone-mounted camera. The video was of a rural site with a problem that I had investigated earlier. The Google Earth photograph was certainly useful but found wanting for detailed, accurate analysis.

I’ve been taking video of accident and failure sites using drones for several years. It’s routine for me now during my forensic work. The video can be taken at any elevation from ground level up to 400 feet, whatever suits the investigation. I’ve told you about this in previous posts. (Ref. 1)

But it was a photograph sent by a client of an urban site in Ottawa taken from Google Earth Pro that opened my eyes. This was the scene of a retaining wall failure. I was able to get a lot of data from the photograph. (Ref. 2)

I also learned last evening over a glass of wine that a friend has been using photographs from Google Earth in traffic accident reconstruction for a long time.

He can draw an accident diagram on a Google Earth scene using a program like FARO BLITZ.  The program contains a file of vehicle dimensions so that vehicles placed on the diagram are automatically drawn to scale. 

Also in the program are the symbols, lines, curves, scales, etc. typical of a land surveyor’s plan. And these are placed on the accident diagram much quicker and cheaper than a surveyor could.

Finally, objects such as vehicles that happen to be in the Google photograph and not needed can be deleted.

A forensic engineering drawing quickly made to order using Google Earth while sitting at your desk.

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This is what’s available from Google Earth Pro for an urban site:

1. High resolution video from a sports utility vehicle, a SUV, on the road in front of the rural or urban site
2. High resolution video from a satellite of a site in a built-up, urban area
3. Video of sites in rural and built up areas that are okay from a satellite but get blurry when you zoom in

The mid range video, #2, in the above is not available from Google Earth Pro for a rural site. This video is taken with very sophisticated cameras on satellites way up high and is excellent for terrain analysis and data collection at a forensic site in an urban area. (Ref. 2)

The stepped procedure for doing this is straight forward:

1. Open Google Earth
2. Enter the civic address of the site into the Search box
3. You are now looking at a high level Aerial View of the property of interest and its surroundings
4. To switch to “Street View”, pull the little person icon from the “ghosted” controls on the top right to the place on the roadway you want to examine
5. You can then rotate your view using those controls on the upper right and can use your mouse to choose to move right or left along the road by clicking on the arrows ( < or > ) which appear on the roadway itself
6. To leave the Street View and return to the Aerial View, choose the “Exit Street View” on the top right of the screen
7. To add a slider to the top left of the screen which shows earlier imagery, choose “Historical Imagery” from the “View” drop down menu at the top

Here is the most direct link to download Google Earth Pro using a PC. I’m not familiar with downloading to Mac, Apple desktop computers. The procedure is in a different part of the Google Earth website.

https://www.google.com/earth/versions/#earth-pro

Summary

You have a wonderful tool at Google Earth Pro to get photographs of a site minutes after a client briefing about an accident or failure in the built environment. If you subsequently retain an expert to determine the cause of the problem you’ll be able to brief him or her in a more informed way. A picture is still worth a 1,000 words. I’m using it now and you can too – you don’t need to be a technical expert.

References

1. A Bundle of Blogs: Aerial video of insurance and forensic sites taken with cameras mounted on drones. Posted October 31, 2019
2. What can you get from a virtual visual site assessment about the cause of a leaning retaining wall? Posted November 13, 2020

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(Posted by Eric E. Jorden, M.Sc., P.Eng. Consulting Professional Engineer, Forensic Engineer, Geotechnology Ltd., Halifax, Nova Scotia, Canada ejorden@eastlink.ca)