Neighbouring Trees and TPOs

[Chris at eden]

11 minutes ago, Jon Heuch said:

Depends what you use to measure your diameter with, but what unit does a diameter tape use? What does every forest mensuration and yield table use? That's because they have scientists, mathematicians and practical statisticians supporting them - they understand what they are doing and trying to achieve. They understand that data collection costs money. Use of an extra digit to report in mm is simply a waste of time & effort. It adds nothing.

I'll say it again.  What i actually said was that tree experts in an Arb context use mm's the majority of the time for surveys when measuring stem dia's.  As a result and just out of habit, after a while they start to discuss tree diameters in mm's.    Not saying this is right or wrong although the imperial system is bonkers in my opinion.  But, your comment was, oh no they don't.  Sorry John but they do.  They don't measure or discuss in inches which was the main point and that i would be concerned by someone claiming to be an Arb expert and saying this Cherry has a stem dia of 40in and it will double in the next 30 years. 

 

I know your background is forestry and knew this was where you were coming from with the comment.  When I first moved off the tools in 2004 I was working out tree heights in feet and then converting them to metres in my head.  I never made a conscious decision to just start doing them in metres but it just happened naturally over time.  But at the end of the day we were not talking about forestry.       

 

Arb also has some well respected scientists do they not?  But, they don't seem to raise the use of mm's to measure stem dia's as an issue.  

11 minutes ago, Jon Heuch said:

 

For a very good reason; they are interested in accuracy in mm when installing buildings, measuring elements of the building to the nearest mm. Not micro metres that a mechanical engineer might be interested in. It's horses for courses.

Why use something different? Well indeed, why has arboriculture wandered off by itself without thinking what was needed? Measurement systems reflect the need for accuracy and precision. Arboriculture gains nothing from trying to measure and record in mm. Nothing, other than larger bills as extra time is required to record an extra, useless digit. Greater potential for error, with an extra digit, repeated thousands of times per year. This is basic data recording theoretical, yet practical stuff.

I can't see how using mm costs me anymore when doing Arb surveys, storing large amounts of forestry data maybe.  Sorry to labour the point, but again not making a case for using mm.  I have no issue with using cm's, inches would be a different matter.  But it is what Arbs mainly do.    

11 minutes ago, Jon Heuch said:

 

As it happens my excel spreadsheet for BS5837 uses mm as the formulas are set up using mm. It's a joke & only done because I know someone may make the comment...well the standard says....

Exactly.  That is the reason I use them.   What is bizarre to me is that the standard says to measure the stem dias to the nearest 10mm and then annex D works them out in 25mm increments.    

11 minutes ago, Jon Heuch said:

 

Recording tree diameters as 15, 20, 25, 30 cm does as you say have the potential to increase RPAs somewhat, if developers ever paid any respect for such measures.

Cant argue with that.  

11 minutes ago, Jon Heuch said:

The significance of this for small trees is very small as branch length is typically greater than RPA radius (so the RPA actually misleads); for larger trees the % change is small. But if you have arb consultants allowing foundations to be dug on the edge of an RPA you need to add as much as you can, knowing how much liberty will be taken downstream.

Or that.  

11 minutes ago, Jon Heuch said:

 

>> No I am referring to a bog standard leyland or lawson cypress with no access to the stem as multiple branches prevent access and in reality it is not possible to distinguish branches from main stem. No need for a second or multiple stem for this problem to occur. Ridiculous to think of a measurement in cm let alone mm.

Or that.  

[Chris at eden]

26 minutes ago, kevinjohnsonmbe said:

I agree, it’s not so much a discussion about how it’s done, but rather why it’s done that way. 

And again, my original comment related to how its done, not why its done!  mm is how its done, that is the only point I made.  I don't really care why its done that way as it doesn't have an impact on me.  If i could change anything from the standard it would be to switch the multi-stem calc back to basal diameter as working those out is time consuming.