TITLE: How to properly roll and store DBH tape measure
DATE: 2018-02-21
AUTHOR: John L. Godlee
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I've just come back from fieldwork in Angola, during which I had to 
measure the diameter at breast height (DBH, 1.3 m) of the trunks of 
about 2300 trees. To estimate the diameter I used a DBH tape, which 
is a type of tape measure similar to that which you would find in a 
tailors, made of frabric or fibreglass. The difference is that a 
DBH tape has two scales, the first is a normal mm scale, but the 
second is a scale which estimates the diameter of the tree trunk by 
assuming the trunk is a perfect cylinder and converting the 
circumference (C) using the formula:

DBH =

There are plenty of resources on best practices for estimating DBH 
using a DBH tape, how to deal with irregular stems etc., the focus 
of this post is instead to show how to properly store a DBH tape to 
minimise tangling and to keep it compact while in a backpack.

The first thing to do is to roll up the DBH tape starting from the 
end with no metal hook, until you have about 20 cm of free end.

  ![DBH tape 1](https://johngodlee.xyz/img_full/dbh/roll_1.png)

Next, pass part of the free end through the hook and pull it 
through.

  ![DBH tape 2](https://johngodlee.xyz/img_full/dbh/roll_2.png)

  ![DBH tape 3](https://johngodlee.xyz/img_full/dbh/roll_3.png)

Then, twist the roll so it sits inside the newly formed loop that 
was pulled through the metal hook. At this point the tape measure 
looks fairly compact, but the tape will be twisted.

  ![DBH tape 4](https://johngodlee.xyz/img_full/dbh/roll_4.png)

Remove the twist in the tape by turning the hook end and make sure 
all parts of the tape are in aligment.

  ![DBH tape 5](https://johngodlee.xyz/img_full/dbh/roll_5.png)

Finally, tighten the hook end around the roll of tape by turning 
the hook around the roll to take up the slack

  ![DBH tape 6](https://johngodlee.xyz/img_full/dbh/roll_6.png)

Like this, the tape should stay together in a rucksack or pocket, 
allowing it to be quickly unrolled to take a measurement, without 
risk of it tangling round whatever else is stored next to it in the 
bag.