Reliable forensic evidence from drone photography; Aerial photos from way-down-low

I continue to be excited about using drone photography during forensic investigations.  The engineer and former land surveyor in me loves the wealth of accurate data in photographs taken a few 10s to 100s of feet above a site where a structure failed or a person was hurt.

We’ve always had photogrammetry in engineering – using photographs taken from airplanes flying many 1,000s of feet above the earth to identify and measure features on the ground.- but we get more and better data from drone photos and get it quicker and cheaper.  The potential uses are something else:

Use #1: Investigating traffic accidents: An engineering colleague routinely sends a toy drone aloft, a 100 feet or so, and takes a photograph of a traffic accident site that he is reconstructing. (Ref. 1)  He sees his site from this angle right away and it guides his investigation as he does his field work.  He can also get a print of his drone photo for his engineering report..

Use #2: Conferring with clients: I conferred with a client a few months ago while both of us had a CD of aerial video of his property uploaded on our computers.  I had mailed the CD to him a few days earlier.  He commented on features on the ground relevant to my investigation of his failure.

In one case he gave the history of the ground at one location – cows drank from a former dug well there in the past – that was important in confirming the depth to the ground water beneath the site.  At the time I couldn’t quite believe what i was hearing about the cows and the dug well – there was no evidence of this when I was on site..

Use #3: Getting data on a site: I emailed a drone photograph to a client recently and asked him to identify the location of buried structures on his property.  Structures like two underground fuel oil storage tanks (USTs), – which leaked oil in the past – a drilled water well, two dug wells, a septic tank and a disposal field.  He did this then emailed the marked up photograph back to me a few hours later.  He used Paint, a program on PC computers.  It was all so quick and inexpensive.

Use #4; Getting BIG Data:: The height or altitude of the drone above the ground when a photograph was taken has always been of interest to me.  Robert Guertin, Halifax who takes my aerial video, found a program that gives a wealth of data on each photograph.  The data includes the height of the drone when the photograph was taken, angle of the photo shot below the horizon, bearing of the view with respect to North and the GPS location, all important data in forensic work.

Use #5: Getting low cost data:  I get the scale of drone photographs now from the known size of objects in the photographs.  Like the length and width of a building or the distance between the lines on a highway.  The scale of the photograph I sent to my client a few days ago that he marked up with Paint is 1″ = 40′.

I can check the scale of a drone photograph by setting out ground control before taking drone photographs, like photogrammetry-of-old.  Ground control is nothing more than points set out on the ground a known distance apart and height above sea level.  I used sheets of white paper to mark points on a site I was investigating in Cape Breton.

Use #6: Photographing hard to get at damage: I recently suggested to a firm who needed an expert that we could record the condition of a damaged wall with a drone photograph.  Later I could measure and analyse the damage in detail and get an idea of the cause – measuring like I do now of the ground but of a vertical surface rather than a horizontal surface.  No step ladders, staging, labour and lots of expensive time needed.  .

Use #7 Replacing expensive site surveys:  The drone photograph with a known scale is certain to replace the need in the future for a site survey by a land surveyor, and be far more detailed, less expensive and quicker.  Site surveys measure the size, location and elevation of objects and features on the ground.  Conventional site surveys can be time consuming and expensive.

Use #8: Seeing a site in 3D: I’m working with Robert to see if we can get a stereo pair of drone photographs of a failure site and using these to view a site in 3D like we’ve always done in photogrammetry-of-old.  Software likely exists now for viewing drone photographs in 3D.  If it’s out there we will find it and I will use it during my forensic investigations.  In the meantime we’re trying to do it ourselves.

(A stereo pair are two photographs overlapping by about 60%.  When viewed with a stereoscope – sort of like eye glasses – the site appears in 3D)

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What more do you want from simple drone photographs?  Name it and the potential for getting it.is almost guaranteed.  Honestly, with all due respect, you or your expert would be remiss if you did not get drone photos of your site.  Your expert would not be conforming to the changing forensic investigative standard of care.

Reference   

  1.  A kid’s toy drone can photograph the site of an engineering failure, a personal injury or a traffic accident.  Posted September 12, 2018

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The two solitudes of expert services

Take your pick: An expert from the great majority represented by Ruth Corbin’s pilot study of 152 experts, or an expert from the fringe, (Refs 1 and 2)

The study found that the majority of experts know they’re serving the court, not the lawyer who retains them nor the lawyer’s client, and they continue to swear oaths to that effect.  The study was carried out because the judicial system continues to disbelieve them.

Fringe experts believe they are serving the lawyer and his client, not the judicial process.  This to the extent that some want to know upfront the technical issues as perceived by the lawyer – no mention of technical issues that the expert might identify – and how much budget money they got.  These questions during a first telephone call don’t resonate well.  I wouldn’t call these experts hired guns USA style but perhaps treading close Canadian style.

The “two solitudes” came to mind when I was chatting with one fellow and this fringe characteristic was reflected in his comments when the question of who we serve came up..  When i asked he was adamant that experts serve the lawyer not the judicial system.

Fringe example #1: Later this chap asked me to join him in responding to a lawyer’s need for an expert to investigate the cause of damage to a structure.  I didn’t think much about it at the time but he only casually referred to the lawyer by his first name as someone he knew, briefly mentioned another party involved and identified the location of the structure.

Based on my colleague’s description of the problem as he was briefed by the lawyer the cause was obvious, an easy initial hypothesis.  I had investigated this type of problem often enough over the years and it’s written up in forensic engineering guidelines on typical civil engineering failures and their cause.

i agreed to join him help resolve the dispute.  He would manage the case he said and I would investigate and confirm the cause of the problem.  He asked and I updated my CV over a weekend and sent it off to him on the Monday, only to learn he had responded to the lawyer on the Friday sans my CV but including his.

On reading his response to the lawyer I saw brief mention of my name.  When I asked he said he would send my CV when the lawyer asked for it.  I also asked several times over the next few weeks for a copy of his CV as presented and the name of the lawyer and his firm but he never gave me this information.  Months later he explained, “With deference, I’m not going to give you his name.  He called me.”.  Tricky, eh?

He’s heard nothing since from the lawyer.  I can’t help but think the lawyer’s smart enough to know my colleague’s engineering background hardly qualifies him to investigate this type of failure.

Nor can I help but think I witnessed fringe behaviour.  This chap is pleasant, well educated and experienced and I’ll consider working with him in the future, for the benefit of the judicial system, but he’s a bit tricky as I learned and we’ll get things out in the open at the get-go.

But, on second thought, I don’t know if perception is everything and I’m seen to be associating with a tricky, fringe expert.  Another forensic engineering colleague on recounting this case to him was quick to remind me of the perception issue.

Following are a few more fringe cases to ensure that you know there is a fringe solitude to expert services.

Fringe examples #2 and #3: I read two expert engineering reports by separate experts, one on the stability of a fill slope and the other on a slip and fall accident.  I cringed at the bias exhibited by the phraseology in both cases in favour of the experts’ clients.  Crass in one case.

You might say there’s a subjective element in an assessment of bias and that’s true.  But I feel more confidant in my subjective assessment after reading about the eight main biases in engineering. (Ref. 3)

I’ve also read and written a lot of engineering reports, research papers and blogs/essays over the years and I sure do know the difference between objective and biased phraseology.  Think most of us do.

I’m also comfortable with the objective evidence in both cases.  In the fill slope case, the expert did not get out of his car to see the large pieces of construction debris at the toe of the slope threatening the stability.  The debris included organic matter like tree stumps that rot away in time and cause a slope to subside a lot.

And in the case of the slip and fall accident, quite apart from his phraseology, the expert’s comments indicated he did not know the standard of care existing in the area for investigating the skid resistance of the floor at an accident site.

(Skid tests are coefficient of friction tests like in high school physics)

(A fill slope is the slope the surface of the soil or another material slumps down to when it’s piled on the ground.  A cut slope is the slope soil takes when we cut into or excavate the ground.  We see cut and fill slopes everywhere along our highways)

Fringe example #4: Would you like to know about a second slip and fall accident that exhibited fringe behaviour?  But, to cut the engineer some slack, possibly because he was new to the expert services arena.

An engineer, a five hour drive from the accident scene, decided the cause of the accident from pictures provided by his client.  He did not travel to the accident site and examine it firsthand nor carry out skid tests.  That would have added to the cost of the forensic investigation.  The judge dismissed the expert’s evidence.

Fringe example #5: Would you like a fifth fringe case; actually a fringe expert?  At least to some extent a fringe expert.  Years ago I heard an expert remark that he “…knows how to work a case up”.  Work it up into a “…juicy case…”.

Is my years-ago colleague practicing near the fringe?  Possibly.  He is good though in his area of expertise and still practising suggesting he’s impartial enough.  The last thing a lawyer wants is an expert that can be made a fool by the judicial process.  My colleague would have gone by the wayside years ago if he was a blatant fringe expert.

There’s no question the great majority of experts serve the judicial system and do this objectively.  Read Ruth Corbin’s paper again.  And it’s no secret there’s a fringe element that serve themselves.

Sadly enough, with all due respect to civil litigation lawyers, some are contributing to maintenance of the fringe solitude.

I attended the Expert Witness Forum East in Toronto in February and gave a talk on the principles governing cost control in civil litigation involving experts.  During a presentation by others I heard a lawyer suggest that experts should be retained on a contingency basis.  That suggestion has got to be out in left field considering that perception is everything in the judicial process.

The suggestion went nowhere in the ensuing discussion.  But the idea is out there and I’m sure there are fringe experts who will pick up on this idea and run with it and help maintain the “two solitudes” of expert services.

Fortunately, the judicial system is getting what it needs from the great majority of experts, whether it realizes it or not.  The fringe just muddy the waters a bit.  Still, the system has got to be on guard against the fringe experts scaling the bulwarks and taking over.  The fringe experts are out there.

References

  1. How experts are helping break the expert witness logjam.  Posted April 30, 2018 (A blog on Ruth Corbin’s  paper, following)
  2. Corbin, Ruth M., Chair, Corbin Partners Inc. and Adjunct Professor, Osgoode Hall School, Toronto, Breaking the Expert Evidence Logjam: Experts Weigh In, presented at Expert Witness Forum East, Toronto, February, 2018 (Google it)
  3. Are experts being being broadsided by bias, unbeknownst to them?  Posted April 12, 2018

 

 

 

Why did the bridge collapse in Italy and how might Advocates have known this could happen?

(There’s take-away insight in this item for Advocates at the case merit assessment stage, particularly in Appendices 1 and 2.  The simple data there plus conferring with a forensic engineer can help you assess the technical merit of a case)

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Right away, three engineers had similar thoughts about the cause of the Morandi bridge collapse August 14 in Genoa, Italy :  My friend, Paul Gunson, Adelaide, Australia, in an email a few days ago, friend, Reg Crick, Halifax, during a chat, and me. (Ref. 1)  Paul drove under the bridge in 2009.

Take your pick of causes from a survey of these people:

  • Water,
  • QC,
  • Maintenance,
  • Water

If that’s not enough, I’ll tell you a little secret below about how designers tweak - some might skimp-on - the factor of safety.  (Actually, it’s good engineering not skimping but you need an informed public to understand that)

(QC as in Quality Control during construction and Water as in Lots of Water)

Paul did some research and found that the Morandi bridge and one other showed serious rusting of the steel reinforcing – too much water and too little maintenance  The concrete cover was spalling in some areas and exposing the steel to the weather.  There were also reports of concrete that was way below the specified strength – too little QC.

I did quite a lot of quality control of concrete and earthworks in the past and Paul’s findings resonate with me.  Quality control and maintenance are not very glamorous and often get the short end of the stick.

In a blog several years ago, I added quality control and maintenance to a list that I saw of the stages in the life cycle of a building or civil engineering work – to increase the total to 11.  There’s no questions they are stages where failure can occur.  Ignore them at your peril. (Ref. 2)

Almost the first thing Reg said when we chatted about the bridge in Italy, “Get rid of the water!! (Stupid!!)”.  Reg didn’t say “Stupid!!” but that was the tone. (Ref. 3)  He was referring to proper drainage of the water from the bridge deck that isn’t provided for during bridge design.  Drainage design isn’t very glamorous.

Reg noted another mutual friend Bill Waugh, who designed dozens of bridges in Nova Scotia and Jamaica before he passed away, despaired at the inattention to deck drainage during bridge design.  Water rusts exposed structural steel..  There’s an element of maintenance in this as well; keeping deck drains – when they are present – clear of debris so the water can drain.

I wondered when I first saw the bridge failure why successive spans of the bridge went down after the first one?  Was that continuous span of bridge deck over successive piers designed to such a low factor of safety – in the interest of looking slender and pretty – that a span relied on adjacent spans for some of it’s support?  And when one span goes down, like dominoes many go down?  But in hindsight I realized that proper design of bridges like this one might in fact rely on adjacent spans, but perhaps too much.

A tweaking engineering design secret: In engineering design the factor of safety is reduced – confidently whittled away – with increasing successful design and construction, and no failures.  Until the pendulum swings too far, failure occurs, the pendulum swings back.and the factor of safety is put back up.  This really does happen in design. (Ref. 4, pages 100, 101. A very good read)

(The factor of safety is a number got from dividing the weight you want to support safely into the greater weight that will break the thing providing the support – cause it to fail)

If you want to know more about when and where failure occurs and who is responsible – a broader picture - see Appendices 1 and 2 below.

It’ll be a while before we know why the bridge in Italy failed but the smart money is going down on over confidence during design and poor deck drainage and maintenance.  And no way can I leave out poor QC during construction.  Any takers?

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There’s food for thought for Advocates in this item.  Buildings, civil engineering works and infrastructure fail in many ways, and some of these are an easy first pick for a forensic engineering expert at the merit assessment stage.  And failure doesn’t have to mean total collapse of a building, – or a bridge like in Italy – but simply that it doesn’t work right.  The bridge probably didn’t work right for years, like in poor deck drainage.

Poor design, construction and maintenance can also injure people, for example, in slip and fall accidents on floors with low skid resistance.

What’s the take-away for Advocates?  You’ve learned that when a failure occurs in the built environment or a person is injured experienced engineers are suspicious of what took place at certain stages in the development of a structure.  Our suspicions are backed up by independent and detailed studies by researchers in the U.S. and Europe of 100s of failures.

Taken together – our experience as engineers and these studies – we have a good idea where to look for cause.  If you don’t consult an expert at the merit assessment stage you risk technical failure of your case.  

References

  1. Personal communication, Paul Gunson, Adelaide, Australia, 2018
  2. Stages in the “life” of a structure helps communication between counsel, insurance claims managers and engineering expert. Posted July 2, 2015 (See update Appendix 1)
  3. Personal communication, Reg Crick, Halifax 2018
  4. Petroski, Henry, To Engineer is Human: The Role of Failure in Successive Design, Vintage Books, New York April 1992,
  5. International engineering magazine publishes information on foundation engineering in eastern Canada – and also information useful to counsel on the causes of failure.  Posted January 4, 2013  (See Appendix 2)

Appendix 1

(The following was taken from Reference 2 above and updated)

You might be interested in the updated list below of the stages in the “life” of a structure in the built environment.  Structures include earthworks and waterworks – a reshaping of the natural environment – as well as buildings and bridges.

I came across the basic list while reading the latest, 2012 edition of Guidelines for Forensic Engineering Practice.  I added the stages in italics to those in the Guidelines.  The list is a useful breakdown of the aging of a structure.

The Guidelines were published by the American Society of Civil Engineers (ASCE).  Civil engineering includes structural engineering and geotechnical engineering.

I see the list providing context and facilitating communication between counsel, insurance claims managers and consultants, and an engineering expert.  Failures and personal injury accidents can occur pretty well any time during the life of a structure.

Principles governing communication between counsel and expert have been developed recently by The Ontario Advocates’ Society. (Ref. 2)  The following list of stages in the life of a structure will further help counsel and an engineering expert talk to one another when a failure or personal injury accident occurs:

  1. Conceptualizing
  2. Planning
  3. Designing
  4. Constructing
  5. Quality control (during construction)
  6. Operating
  7. Maintaining
  8. Renovating
  9. Re-configuring
  10. Decommissioning
  11. Demolishing

ASCE say that, “Failure can be defined as an unacceptable difference between an actual condition or performance and the intended or reasonably anticipated condition or performance.”  This can occur during any stage in the life of a structure.

Furthermore, “Failure need not involve a complete or even partial collapse.  It may involve a less catastrophic deficiency or performance problem, such as unacceptable deformation, cracking, water- or weather-resistance, or other such phenomena.”

It’s not difficult to imagine that failure can occur at any stage.  Nor that personal injury accidents can occur at any stage.

Communication is easier for both counsel and client and counsel and engineering expert if we all have an idea of a structure’s “life” and the stages it goes through as it ages  The list above can help us.

Appendix 2

(The following was taken from Reference 5 above)

An article entitled “The expert witness and professional ethics” reports on the categorizing and classifying of the causes of structural failure as determined by researchers in the U.S. and Europe.  This research reviewed the causes of hundreds of failures.  Based on the research the primary causes of failure were categorized as follows:

  • Human failure
  • Design failure
  • Material failure
  • Extreme or unforeseen conditions or environments
  • Combinations of the above

When professional engineers were at fault (human failure) the causes of failure could be classified as follows:

  • 36%…Insufficient knowledge on the part of the engineer
  • 16%…Under estimation of influence
  • 14%…Ignorance, carelessness, negligence
  • 13%…Forgetfulness, error
  •   9%…Relying on others without sufficient control
  •   7%…Objectively unknown situation
  •   1%…Imprecise definition of responsibilities
  •   1%…Choice of bad quality
  •   3%…Other

When the percentage distribution of the failures were summarized the research found that almost half were due to errors in the planning and design of a structure and a third occurred during construction:

  • 43%…Planning and design
  • 36%…Construction
  • 16%…Use and maintenance
  •   7%…Others and multiple factors

I reviewed research a few years ago that found many, possibly most, foundation failures were due to inadequate geotechnical investigation of the foundation soils.

This type of information based on what appears to be quite exhaustive research is valuable to a forensic engineer in forming an initial hypothesis of failure at the beginning of an investigation.

The information is also valuable to Counsel in assessing whether or not to take a case or gaining an appreciation of where a forensic investigation may be leading based on initial oral reports by the professional engineer investigating the cause of the failure.