Thermal Imaging Camera's

[christreeroot]

as someone else said i dont see how it works, the tree will look different in snow than i will in a baking hot day. alot to prove imo

 

 

As i see it the user monitors the conditions and applies it to the software. This was a concern of mine but after a chat with Marcus showed it has been well thought of and dealt with.

[ScottF]

Hi Scott - have a look at the thread in the link above - some input from Marcus Bellet-Travers on there who is the main dude in terms of this technology.

 

Thanks, MisterTree. I've had a scan at some of the articles written about it now (many being written by Dr Giorgio Catena from 1989 to present, the guys who seems to have pioneered it) and they all seem to suggest that the data you'd get from IR relate to, effectively, vascular conductivity (as MonkeyD spotted earlier in this thread). What concerns me is that this device seems to be (correct me if I'm wrong or have got the wrong end of the stick) marketed as an internal decay detection device. I would welcome any tools that would help to to determine the extent and location of vascular disfunction in a tree (think bleeding canker or as a tool to identify and limit the spread of DED), but disfunction in the thin layer of conductive tissue of tree doesn't mean that the underlying static tissue is compromised- there just isn't always a direct relationship. If I've got this wrong anyone, feel free to explain it to me. Cheers

[Paul Barton]

Hi Scott. I think you have hit the nail on the head - I don't think this intended to be a decay detection device in the sam way as Picus is and therefore should not be marketed in that way.

 

From what I understand (which is always limited) the device is more helpful in determining overall health as represented by the ratio of functional/dysfuntional tissue. It will pickup cankers before they are visible as you point out.

 

I think it will show internal decay as well though. Because dead cells have less conductivity between them, they dissipate heat at a different rate. Therefore cool areas on the surface can indicate areas of dead/decaying wood underneath. This would be helpful when looking at bases of trees or branch unions. However I think it is still prudent to investigate significant cool (ie possibly decayed) areas using a resistograph for example.

 

The nice thing is that it is possible to survey large numbers quite quickly and in a non-invasive way.

 

..and then there's the potential for investigating bat roosts etc...

 

Hope this makes sense?

[ScottF]

Much clearer. As I said, I think as a means of investigating vascular disorder (the least understood set of disorders, possibly), it's probably about the best thing I've seen.

As for correlating with decay, like you say, it's not so clear. Dead conductive tissue doesn't automatically equal compromised static material below. And vascular disorders can "rewire" themselves in many cases, too.

It would be really interesting to take a series of IR shots of a representative sample of genera over time to see what goes on as the tree matures/declines.

[Paul Barton]

It would be really interesting to take a series of IR shots of a representative sample of genera over time to see what goes on as the tree matures/declines.

 

Agreed. I am sure as the technology is used more the bank of images that come out of it will be very enlightening.

[ScottF]

Agreed. I am sure as the technology is used more the bank of images that come out of it will be very enlightening.

 

I feel a very "anoracky" picture thread coming on...

 

excellent

[Treefitter]

Thank you all for your help. Maybe a portable X-ray?!

[Marcus B-T]

OK I've seen what people have written and here are some answers. The first thing that you all need to think is not 'why the surface temperature of something indicate an internal fault' because in thermal imaging terms this concept is nothing new and has been applied to many other applications already and I will deal with this either in a moment if I have time or in another posting.

 

The thing that is remarkable is that a healthy tree has a relatively even surface temperature, because it realy shouldn't. There are so many changes in ambient air temperature, soil tempertaure etc going on all the time that realy the surface temperature should be a mixture of areas with different surface temperatures but it isn't! SO why is this? Well little did we know but trees have a very efficient 3 dimensional heat transfere and transport system. The vascular system is part of this but 'only' part of it and the sap wood and central wood volumes such as heart wood are all part of it. So why should a tree need this? well if it didn't, the growth of a tree would be increadibly uneven and you couldn't have big trees. Cell metabolism including growth is temperature dependent, because trees do not produce heat themselves they require heat from the environment to drive metabolic chemical reactions. To illustrate this think about how slow crop growth is in cool spring weather even if there is plenty of sunshine. So the tree needs to augment and transport environemntal heat efficiently to activate cell metabolism. This is just as important on the sunlit side of trees as on the shaded side, except here there is also the need to disipate excess heat which will kill cells. This is why trees have a very efficient heat tranfere system that moves heat to and from the surface.

 

If we didn't have this then the temperature would not be even, also without it extreme temperature gradients will be set up in side the tree. The gradients set up will cause depressions in surface temperature. Guess what, this is what thermal imaging picks up.

 

The problem is that what we are told and anticipate in terms of heat metoblism of trees is generally wrong. We think of most tree systems in over simplistic ways and forms. Did we realy think something as large and complex as a tree would revolve around simple systems? If it did it would die the day the seeds germinated.

 

Ted Green thinks we are on the dust cover of the book of trees; we havn't even got a publisher to take the book seriously!!!

[ScottF]

Well, Marcus, to be honest I'm none the wiser about how your system is meant to work after having read your explanation. Could you please clarify how your device and/or software detects internal decay in trees because that's clearly how it's being marketed.

 

Is there any peer-reviewed research which shows a statistically significant relationship between the findings of IR and actual mechanical failure in trees? Is it in any way legally defensible?

 

I'm really not having a go- I just want to understand how this system is meant to work.

 

cheers

[Marcus B-T]

OK as I promised yesterday this is how it works. The tree has a very complex system for heat transport that acts as a moderator of the effects of external temperature. The system is improved by the presence of the vascular system but works even without it because the vascular system is only part of the heat moving system. Therefore, it works in winter and summer. It has to be complex because if the tree relied just on insulation it would not grow in the spring because it would take too long to warm up; and in the summer heat would become trapped and fry the tree. For similar reasons the system has to work when transpiration is low or has stopped because again trees would take too long to respond to temperature. You could not have a system that just used the vascular system because it switches on and off throughout the year and throughout the day making it very inefficient.

 

The whole system is driven by changes in environemental temperature, so that it doesn't matter what the actual temperature is as long as it changes, Which it does every day between dawn and midday and vice versa.

 

Just a point here before I continue, that is why you need the software to calibrate the images, because every day the temperature changes are different and there are difference for some species as well.

 

So, we have a system that moves heat around the tree, but this is not the end of it. The heat dosen't just move up and down the tree it moves in and out of the stem; from all but the most inert heart wood, through the sap wood and vascular system to the surface. So you have both longitudinal and radial heat movement in response to changes in environmental temperature.

 

As this happens you get a heat gradient from the centre to the outer surface, which again if the tree functions well is relatively even. But, if something gets in the way that does not conduct heat well it reduces heat flow so that heat moving to and from the surface is restricted. This causes the surface to be relatively cooler in areas where the heat doesn't move to and from it as efficiently. The closer the surface is to the anomoly the greater the effect. That is why the greatest effect is from cankers at the surface.

 

Decay and cavities have a profound effect on temperature because they heat up and release heat very slowly so there is a big differential between healthy functional tissues and the affected areas. This becomes apparent at the surface because the reduced heat movement to the surface reduces surface temperature. The bigger the volume of decay, the more it alters temperature movement, the more it alters surface temperature.

 

Again to understand it properly you need to calibrate images against environmental temperature.

 

Other barriers such as inclusions, splits etc have localise distinct effects. So with training you can actually differentiate between differt kinds of anomaly.

 

This is why you can use it for decay detection but the emphasis is on detection not investigation or confirmation. None of the decay detection methods can investigate or confirm decay!!

 

In addition no decay detection method can tell you if a tree is likely to fail, this is a matter of the balance between wind forces and static forces applied to the tree on the one hand and the resisting forces of the tree on the other. This MUST be determined by mechanistic or statistical means.

 

I can't think of any publication where decay detection equipment been a directly compared to actual tree failure, i.e. trees where pre-tested and then allowed to fail and quite rightly so since this would misslead people into thinking we have tree failure detection methods, and this would be a nonesence . BUT we have done this as part of the process of checking for incedences of false positives, i.e. the technology says there isn't a decay when there is. We have carried out measurements with IR on over 20,000 trees and around 8,000 of these were either felled or had increment cores taken to confirm the findings. We have had zero false positives and because IR is a direct measurement of tree health this is quite understandable. We have had low incedence about 1 in 3000 false negatives i.e. it looks like decay when it isn't but this is caused by large volume of included rubble or dead/dried wood and we now know what this looks like and so false negatives are very rare. I emphasise that this is decay detection and not confirmation so we always recommend an invasive study before felling but this must be done what ever the method you use for decay detection.

 

We have presented our findings to our peers at conferences in Turin and Coventry and we will soon be publishing our findings in journals but this is a natural process and takes time. We are always glad to discuss our findings and technology.

 

The best bit about thermal imaging though is the fact that because it measures temperature it actually measures the balance between tissues with optimal health and tissues that are sub-optimal, so that you get a balance between the two and an appreciation of how robust the tree is to both the environment but also to any work done to it. Therefore it is much more flexible than just a method of decay detection. Also it looks at the whole system from surface to interior. It does have limitations and we accept this, but it also has a wealth of possibilities. If anyone would care to take the time to see the technology in action and explained in detail this can be arranged all you have to do is ask.