very basic dbh question

[TimberFrank]

When measuring dbh and when consulting FC charts to work out volume etc..., do you use whole numbers for dbh or do you use decimal places? How precise are you supposed to be or does it not matter? What's the usual way of measuring it and using it for calculations?

 

The reason I ask is cos I was recording it with decimal places (like say 50.7cm) and then consulting various charts, for example the tariff number alignment chart in the blue book, and instead of setting the ruler at 50, I placed it at what I estimated was 50.7. I now think that might have been erroneous?

[Spruce Pirate]

Pretty sure the usual rule is round down for everything to do with timber measurement, so your 50.7 would be 50. Even on the cusp of 50 and 51 the rule would be round down to 50.

[TimberFrank]

Pretty sure the usual rule is round down for everything to do with timber measurement, so your 50.7 would be 50. Even on the cusp of 50 and 51 the rule would be round down to 50.

 

Ah right, thanks. So would that make my previous calculations inaccurate?

 

(FC Timber Measurement book says, 'In cases where the zero point [of the DBH measuring tape] falls on the dividing line between two diameter classes, the higher diameter class should be used.') But that is for a tape which is marked in rounded down 1cm diameter classes...

 

So it seems the diameter class is what is actually recorded from the dbh field measurement? That's news to me! I didn't realise that you rounded down.

 

Is a rounded down 1cm diameter class tape the same as a standard dbh tape except it hasn't got the divisions?

Edited April 3, 2012 by TimberFrank

[Spruce Pirate]

(FC Timber Measurement book says, 'In cases where the zero point [of the DBH measuring tape] falls on the dividing line between two diameter classes, the higher diameter class should be used.')

 

Yes, you're right. Must remember that!

 

I'm pretty sure that as a general rule you would round down, fairly certain this applies to log measurements. All of a sudden what I learned at college seems a long time ago.

 

The best rule would seem to be, if in doubt - check the blue book.

[TimberFrank]

Yes, you're right. Must remember that!

 

I'm pretty sure that as a general rule you would round down, fairly certain this applies to log measurements. All of a sudden what I learned at college seems a long time ago.

 

The best rule would seem to be, if in doubt - check the blue book.

Yeah me too - I forget the basics I learned in college too! If it isn't used, it is forgotten.

 

Thanks for your help.

[Andy Collins]

Agreed, always round down

[Charlieh]

I was always told to round down, better to under estimate than to over estimate and either disappoint a woodland owner or sell to much in advance then find out your short

[NI Tree]

yes you round down aka truncate

[TimberCutterDartmoor]

Pretty sure the usual rule is round down for everything to do with timber measurement, so your 50.7 would be 50. Even on the cusp of 50 and 51 the rule would be round down to 50.

 

Agreed, always round down

 

Yep. Same with top diameter; even numbers.