Ranger sticks
The forester's stick is an aid for measuring or estimating tree heights (see height measurement ).
It can be made with very simple means and hardly requires any knowledge of mathematics . It was popular with forest workers and is an almost forgotten measuring device .
The disadvantage next to the uncertainty that always a "measurement assistant" with a scale , usually a folding rule and possibly a piece of chalk is needed.
The forester's stick uses the idea of determining 1/11 of the apparent tree height, marking it on the tree, measuring it and converting it to the actual tree height by multiplying it by 11.
The stick consists of a bar or similar that is 11 base units long and on which the route of one base unit is marked. If the base unit is e.g. B. 5 cm, the stick is 55 cm long and has a mark at 5 cm.
Due to the laws of perspective , an object appears smaller the further away the observer is from this object. So it is possible to "fit" the height of a tree into the length of the stick held vertically on the outstretched arm, if one is far enough away. The marking must be provided at the lower end of the stick.
The measuring assistant is instructed by shouting to put a mark on the tree trunk (or to hold the hand / finger there) where the mark can be seen from the perspective of the person measuring.
If this height on the trunk is multiplied by 11, the person measuring gets the approximate height of the tree.