arb culture
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Everything posted by arb culture
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Thanks Tony Using a calculator your sum with the ten trees can be worked like this : change 9/10 into 0.9 (it's the same thing) Then, rather than 0.9 x 0.9 ...etc type in 0.9 then the xy button then 10 then = For the 1:10,000 question you use 0.9999 rather than 9,999:10,000 to work out the probability of a tree not falling over. Then type in 0.9999 xy button 10,000 = 0.368 1-0.368=0.682 = 1:1.582
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spot on:thumbup: Are you a QTRA user?
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decay detection, weapon of choice?
arb culture replied to Tony Croft aka hamadryad's topic in Tree health care
You should easily make that back (and more) if you work hard and work clever. Good luck! -
Tony - are you are QTRA licensed user?
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Tony - you're right it is about cumulative risks. It is a thought excercise exploring the maths though. Let's assume that the target will be replaced by another target if the first one is destroyed/killed. Or that the target is spread over many people wjo visit infrequently and that the death of one person will not affect the numbers of visitors to the site.
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It's just a stats thing. I'm curious as to to how many QTRA users actually know how to deal with mutliple risk (ie more than one tree). Are there any QTRA users brave enough to provide us with an answer?
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Bundle - please don't go. I'm not saying anyone is thick. Would be nice to hear how QTRA users tackle this problem though. If a landowner has 10,000 trees and by some bizarre coincidence all the trees come up in a QTRA assessment as having a 1:10,000 chance of killing someone, what is the chance that at least one of the trees will kill someone?
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Sorry:blushing: I thought your stick and boot hillbilly post was funny. I'll try and use more little faces from now on.
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Nice! Perhaps we should wait and see if any of the QTRA users on here can answer the question?
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Much closer. Are you a QTRA licensed user?
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No, not 1:10,000. The correct answer might surprise you though...
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I look forward to reading them, thanks for keeping us up to date.
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decay detection, weapon of choice?
arb culture replied to Tony Croft aka hamadryad's topic in Tree health care
Andrew - I think you must have read a different set of TPO legislation to me. TPO'd trees are usually removed without the level of evidence you seem to think is required. Hamadryad - If I were you I'd wait until after you've done some of the training you are discussing in other threads, and more importantly - do some market research to see if the level of investment would be returned. At the moment I do visual inspections and call in others to do Picus etc if required. In the last three years I haven't had a single incident requiring more than a sounding hammer (rubber mallet) and a probe (long metal rod), along with my own knowledge and experience. I am very glad that I didn't invest in expensive decay detection equipment, I don't think I would have seen a good return. -
Hamadryad - You need to do a course with some sort of nationally recognised assessment at the end of it to prove that you are actually competent to inspect and make recommendations about trees. As far as I am aware the LANTRA PTI is the only short course available which meets this criteria, so that's the one you should do. Good luck with it, whatever course you decide to take.
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Bundle - Don't take this the wrong way, but have you ever read the book 'Living with Risk' which QTRA so often quotes? I have a big suspicion that very few QTRA users have. I also suspect that very few QTRA users understand the maths which QTRA is based on. For instance (and obviously just as a thought exercise): if you have 10,000 trees and each of them have at least a 1:10,000 chance of killing someone over the next year, what is the chance that at least one of them will kill someone over the next year?
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Dave, I've used the Kirklees one before and Barnsley have accepted it.
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Thanks Marcus, I think this is a very interesting subject, and I'd love to read about it in more detail. How can I get hold of your papers on this?
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Marcus, Thanks for taking the time to put your thoughts on the forum, it's interesting. I understand the issue of confidentiality, but I am not asking how your program works. What I'm really interested in is how you decide whether or not a tree is likely to fail. And more importantly; how do you back this up with your scientific research. I have no doubts that thermal imaging can show where there areas of decay or defective wood, but what I can't work out is what do you do with that information? Do you use a T/r ratio, how do you incorporate reaction growth, how do you factor in wind exposure, tree shape, open cavities, decay type, etc? If this method of calculating the likelihood of failure (or even the proof that the mystery method works) is going to be included in your paper, then brilliant - I'll wait until it's published.
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Andrew, I'm sitting on the fence on some of the thermal imaging stuff at the moment. As you say, thermography as a method of detecting defects has been peer reviewed time and again and seems to work well if used properly. What hasn't been peer reviewed is the system promoted by Tree Projects Ltd. As I understand it this uses a very different method and incorporates a risk of failure protocol which also hasn't been peer reviewed. I'd be very happy to be proved wrong though.
