I was impressed a few months ago by the unexpected\u00a0evidence I got from video of a site taken from a drone.\u00a0 Impressed to the\u00a0extent that I flew another site\u00a0a\u00a0few days\u00a0ago, but this time looking for the “unexpected” evidence.\u00a0 The experience confirmed the importance of filming the site of a forensic investigation from a low flying drone.<\/p>\n
A few months ago<\/em> <\/strong>I\u00a0videotaped a compact site – couple of\u00a0100 feet square – for record purposes.\u00a0 I\u00a0did this\u00a0for\u00a035 minutes from several 10s of feet. On looking at the video I saw a feature of interest relevant to the problem I was investigating.\u00a0\u00a0It was not evident when I\u00a0walked\u00a0across the site\u00a0in an\u00a0earlier visit.<\/p>\n Talking with the property owner later I learned that the feature seen in the video marked a characteristic of the ground that was very important to understanding the problem I was investigating.<\/p>\n A\u00a0few days\u00a0ago<\/em><\/strong>, I video taped a long, narrow site – 1,500 ft.\u00a0x 200 ft. – from an altitude of\u00a0several 100s of feet as well as 10s of feet.\u00a0 This time, however, I\u00a0looked for a feature in\u00a0the video\u00a0that I had\u00a0seen on the ground at one end of the long site.\u00a0 It was relevant to the problem I was investigating.\u00a0 I found it, then studied the video for the occurrence of the feature elsewhere along the length of the site and noted these locations. This was sort of the reverse of the situation at the compact site.<\/p>\n Put another way, a few months ago<\/em> I identified a feature of interest in a video, and had it confirmed on the ground.\u00a0 A few days ago<\/em> I identified a feature of interest on the ground and had\u00a0its location elsewhere\u00a0on\u00a0the site confirmed\u00a0with a video.<\/p>\n ***<\/p>\n This process is called terrain analysis<\/em> in engineering:<\/p>\n For example, how does the strength of the subsurface soils relate to the foundation failure of a building, bridge or highway?\u00a0 Or the subsurface drainage characteristics relate to the location of fuel oil spilled\u00a0on the ground some time in the past?<\/p>\n I’ve\u00a0done\u00a0terrain analysis for years\u00a0using aerial\u00a0photography often taken from 6,000 feet – a long way up.\u00a0 It has been useful – but not at all, at all like the detail you get from low level drone photography.<\/p>\n ***<\/p>\n The\u00a0drone videotaping at\u00a0the compact and long sites\u00a0was similar.\u00a0 Take orientation video from the four sides of the site from a high\u00a0altitude then close up video of different features\u00a0at a low altitude.<\/p>\n I’ll study the video of the\u00a0long site in greater detail then select optimum places on the ground – representative and cost effective – for collecting subsurface data and solving the problem I’m investigating.\u00a0\u00a0The data won’t really be “unexpected”.\u00a0 I’ll get what I expect to get – the depth to the water table, and water and soil samples for testing.<\/p>\n The unexpected evidence a few months ago reminded me about the value of aerial photography in forensic engineering investigation, and the greater value today of low level, drone photography. \u00a0I was also reminded to be on guard against the tyranny of the obvious, to expect the unexpected in forensic work.<\/p>\n \u00a0<\/span><\/p>\n","protected":false},"excerpt":{"rendered":" I was impressed a few months ago by the unexpected\u00a0evidence I got from video of a site taken from a drone.\u00a0 Impressed to the\u00a0extent that I flew another site\u00a0a\u00a0few days\u00a0ago, but this time looking for the “unexpected” evidence.\u00a0 The experience … Continue reading \n