Free to local authorities

[Marcus B-T]

I have been persuaded to offer the height vs dbh programme free to local authorities. You will still need to register by either emailing your details to [email protected] or sending a private message on this web site to marcus b-t.

[arb culture]

What's the height v dbh programme?

[Marcus B-T]

The program uses the realtionship between tree height and stem diameter at breast height to determine the likelihood that a tree will fail see the link below for just some of the huge amount of science behind this.

 

Tree Consult

 

There are two ways of using this relationship, 1. is to gather information of individual trees and try to calculate the mechanical strength it might have using a complex model the problem with this is that you need some pretty acuarte measurements of the degree of sheltering, the wood strength, etc, etc.

 

2. is to gather the actual height and dbh data for a large sub-sample of the trees you want to assess. So you measure the height to dbh ratio of around 2000 tress in a city, and then you have a description of the population against which you can compare an individual tree. This is a time consuming process but is a highly robust way of doing it. Once you have this data you can then look at the influence of stem thining (decay) and stem dying and splitting (a form of dysfunction). You then have a universal data set for your city. With 2000 trees it gives you confidence upto 95% of the population, but you can then build on this database over time and increase that up to 99% etc.

 

So how did I manage to create data bases for so many cities in the UK? Easy, I used Google Street. Since you only need a ratio to start with you can take the data straight from the images. It still takes a fair amount of time and dedication but now I have the data it can be constantly improved up.

 

So what is the big deal with this? Well it means if you have a tree that becomes exposed, you have a robust way of deciding A) it is like most of the rest of the population so no need to think it will fail, B) it is like 5% of the population that are at the limit of the ratio so time for further analysis.

 

The same goes for trees with basal decay.

 

What does it mean? It means that far fewer trees require work, and we have greater confidence in our decisions.

 

It is also exactly what we already do with VTA we look at the size of the tree and the amount of decay (for example) and then decide does it need reducing or not?

[Ian Flatters]

Now i maybe missing the point of this program but as you say at the bottom 'It is also exactly what we already do with VTA we look at the size of the tree and the amount of decay (for example) and then decide does it need reducing or not?' Why would you bother investing £150+vat for something you can go hmm well i'll reduce it, to be told you should reduce it by a program?? Personally id prefer to look at a tree get my clause book out give it a wack. If im worried about the decay more than i normally am it would get a picus used on it. Now i would also like to see the legal row if a council uses this type of program and it says its ok then it falls over too. Who gets the blame?? Atleast if its a surveyor/consultant they get the blame.

 

Im not having a dig or anything and its ment as its me not quite understanding your product and how it differs from just a tree condition survey?

[Marcus B-T]

Fantastic post (being serious here). Point one is that it is not £150 if you are a local arb working within one region it is only £15 and you get the data for your local area, if you are a national outfit then you pay £150 for the full UK package. Also it's free to LA's.

 

It's like this (and I speak from the experience of my self and a number of other highly experienced arb consultantants here who asked me to come up with this, they have been testing it and continue to test it by the way), This does not replace VTA or the assessment procedure, it uses the data you gather to give you a robust statistical outcome, now if you take that to court then it is better than any expert opinion for a start. It basically says that when I compared the tree I am looking at to the trees around it then it was no different to almost all the trees around it. They are still upright and have been so for as long as any one can remeber so why should this one be considered any different. This is a very powerful argument and ranks even higher than the argument I used VTA and identified a defect or not as the case may be. So that is the legal stuff covered. Just to reiterate at this point that VTA or some kind of visual assessment is the starting point.

 

So why did the experts ask me to produce this. Well two issues. The first is if a tree is recently exposed by a tree removal or a tree removal is planed. Question then is are the remaining trees robust enough to withstand the recent exposure. This is a very difficult thing to judge by eye and the common outcome is that some of the remaining trees are canopy reduced in some way. So if you have a robust tool that demonstrates that the trees are no different to the maority of the population then the need for reduction is removed (robustly and scientifically).

 

Next scenario is that there is a moderate amount of decay found at the base of the tree using PICUS, resistograph or thermal imaging, or a mallet if you wish (take your pick here). The question then is has the tree naturally retrenched in response to this, is like the majority of the population and therefore no work required; or is it disproportionately tall for its DBH and therefore potentially a candidate for canopy reduction.

 

The ultimate test to this system is this, do we see large numbers of trees falling dwn every year, answer no. Why is this? well accoriding the the experts (Matteck, Wessolly, Clark, etc, etc) the structur of some trees predisposes them to excess forces that cause them to fail. How do you find out which ones are predisposed? Measure them. If you measure enough you have a description of the population, statistically you look to the extream of the relationship till you find the members of the population that are predisposed. Once you have this, you have a model that tells you explicitly where the limits are. Then you measure and individual in that population and compare it to the model.

 

SO you are probably wondering what the catch is now, well about 30 sleeples nights gathering all the data, and also the model is only valid for the population you have measured, so each population needs to be described in turn, a big job that has taken me about a year to do. I am working with some of the eminant abs I refered to earlier to put together a science bit to explain it in more data.

 

By the way id you think the model cannot work then you will have to throw all your Matteck and Wessolly books away sisnce they advocate this approach.

[Ian Flatters]

Fantastic post (being serious here). Point one is that it is not £150 if you are a local arb working within one region it is only £15 and you get the data for your local area, if you are a national outfit then you pay £150 for the full UK package. Also it's free to LA's.

 

It's like this (and I speak from the experience of my self and a number of other highly experienced arb consultantants here who asked me to come up with this, they have been testing it and continue to test it by the way), This does not replace VTA or the assessment procedure, it uses the data you gather to give you a robust statistical outcome, now if you take that to court then it is better than any expert opinion for a start. It basically says that when I compared the tree I am looking at to the trees around it then it was no different to almost all the trees around it. They are still upright and have been so for as long as any one can remeber so why should this one be considered any different. This is a very powerful argument and ranks even higher than the argument I used VTA and identified a defect or not as the case may be. So that is the legal stuff covered. Just to reiterate at this point that VTA or some kind of visual assessment is the starting point.

 

So why did the experts ask me to produce this. Well two issues. The first is if a tree is recently exposed by a tree removal or a tree removal is planed. Question then is are the remaining trees robust enough to withstand the recent exposure. This is a very difficult thing to judge by eye and the common outcome is that some of the remaining trees are canopy reduced in some way. So if you have a robust tool that demonstrates that the trees are no different to the maority of the population then the need for reduction is removed (robustly and scientifically).

 

Next scenario is that there is a moderate amount of decay found at the base of the tree using PICUS, resistograph or thermal imaging, or a mallet if you wish (take your pick here). The question then is has the tree naturally retrenched in response to this, is like the majority of the population and therefore no work required; or is it disproportionately tall for its DBH and therefore potentially a candidate for canopy reduction.

 

The ultimate test to this system is this, do we see large numbers of trees falling dwn every year, answer no. Why is this? well accoriding the the experts (Matteck, Wessolly, Clark, etc, etc) the structur of some trees predisposes them to excess forces that cause them to fail. How do you find out which ones are predisposed? Measure them. If you measure enough you have a description of the population, statistically you look to the extream of the relationship till you find the members of the population that are predisposed. Once you have this, you have a model that tells you explicitly where the limits are. Then you measure and individual in that population and compare it to the model.

 

SO you are probably wondering what the catch is now, well about 30 sleeples nights gathering all the data, and also the model is only valid for the population you have measured, so each population needs to be described in turn, a big job that has taken me about a year to do. I am working with some of the eminant abs I refered to earlier to put together a science bit to explain it in more data.

 

By the way id you think the model cannot work then you will have to throw all your Matteck and Wessolly books away sisnce they advocate this approach.

 

Ah ha i get it now. Cheers for the swift reply:thumbup1: