Root Protection Area

[shailagh]

Naive question here perhaps so bare with me...  I understand the RPA is 12 (or 15) times the diameter.  However if the diameter tape only shows diameter so how or rather why do they ask it in meters x 12?  Is there a way to convert diameter to meters that I'm not aware of? Lastly, is the calculated RPA outcome measured in meters as well?   
Thanking you for any clarification*

[Khriss]

Take a 500mm diameter tree at breast height, or 1.5m if you have no breasts like me, x12 is 6000mm or 6m,  double this if you want to actually protect the tree's health. Mark it out with powdered lime and photograph it, then file yr report on that day before Johhny Diggerman parks his Taeki ouchi in the zone n drips deisel all over. K

[daltontrees]

1 hour ago, shailagh said:

Naive question here perhaps so bare with me...  I understand the RPA is 12 (or 15) times the diameter.  However if the diameter tape only shows diameter so how or rather why do they ask it in meters x 12?  Is there a way to convert diameter to meters that I'm not aware of? Lastly, is the calculated RPA outcome measured in meters as well?   
Thanking you for any clarification*

RPA is an area in metres squared. I expect what you mean is the RPA radius (RPAr) in metres.

Diameter tapes actually measure the circumference in units of Pi.

If R is the RPA radius, it equals 12 x diameter.

Circumference  C = Diameter x Pi.

Rearrange and solve for R

R = 3.8 x C.

The NJUG guidance rounds this up to 4. So basically unsophisticated workies just need to wrap a rope  around tree stem and go out 4 lengths of that and do a circle round the tree. No tape required.

 

Or if you insist in converting circumference to diameter, measure circumference in metres with  normal tape, divide by 3.14 to get diameter, then multiply by 12 to get RPAr.

[shailagh]

21 hours ago, daltontrees said:

 

Grateful for your responses.*

 

I understand what diameter (circumference x3.14) is, however what is the actual measurement I should give at the end of a diameter reading (cm,metres, mm)? - So simple and yet I'm "stumped".

Before circling the tree do i take the calculated length reading out from the tree in Meters?

 

I'll admit the rope x4 is too handy of a trick;) 

 

[AA Teccie (Paul)]

Obviously the "actual measurement" will vary dependent upon the stem dia. but 'metres' is the norm in my experience.  

[daltontrees]

On 05/01/2021 at 19:54, shailagh said:

Grateful for your responses.*

 

I understand what diameter (circumference x3.14) is, however what is the actual measurement I should give at the end of a diameter reading (cm,metres, mm)? - So simple and yet I'm "stumped".

Before circling the tree do i take the calculated length reading out from the tree in Meters?

 

I'll admit the rope x4 is too handy of a trick;) 

 

BS 5837 says diameter is to be stated in mm, rounded to nearest 10. Otherwise use whatever units you want. Our american cousings rather primitively use feet and inches and so if they measure the diameter in inches they just have to use a RPAr of that number in feet.

 

I don't understand your second question.

 

[Chris at eden]

On 04/01/2021 at 20:44, shailagh said:

Naive question here perhaps so bare with me...  I understand the RPA is 12 (or 15) times the diameter.  However if the diameter tape only shows diameter so how or rather why do they ask it in meters x 12?  Is there a way to convert diameter to meters that I'm not aware of? Lastly, is the calculated RPA outcome measured in meters as well?   
Thanking you for any clarification*

You measure diameter at 1.5m above ground in mm, to the nearest 10mm.  Diameter tapes will have diameter on one side and girth on the other.  Multiply it by 12 for single stemmed trees and then use that as a radius (in metres).  You should really be taking RPA measurements from annex D which bizarrely uses 25mm increments after asking you to measure to the nearest 10mm!!!  Offset if site conditions require it.     

 

Don't over think it, it is that simple.  Otherwise, multi stem calculations are going to blow your mind.

 

Cheers 

 

Chris  

[Chris at eden]

On 04/01/2021 at 21:04, Khriss said:

Take a 500mm diameter tree at breast height, or 1.5m if you have no breasts like me, x12 is 6000mm or 6m,  double this if you want to actually protect the tree's health. Mark it out with powdered lime and photograph it, then file yr report on that day before Johhny Diggerman parks his Taeki ouchi in the zone n drips deisel all over. K

Be careful with the term DBH.  Its a forestry measurement at 1.3m, not relevant to BS5837.  You may end up with over sized RPAs which is not ideal.  

 

Cheers 

 

Chris  

[Khriss]

21 minutes ago, Chris at eden said:

Be careful with the term DBH.  Its a forestry measurement at 1.3m, not relevant to BS5837.  You may end up with over sized RPAs which is not ideal.  

 

Cheers 

 

Chris  

Me fighting for the trees corner again ! K

[shailagh]

Really appreciate everyone taking the time to respond to my seemingly simple questions.

What I'm trying to attain is why its asked in other measurements (mm) when its a diameter measurement. In the end I reckon I'll simply line up the diameter tape measurement with a standard tape to get the mm...

Thanks again & Keep her lit*