Relascope

The relascope, invented by Walter Bitterlich, is a multi-use instrument for forest inventory.

This instrument is used mostly for applications involving variable radius sample plots in a forest survey.

[1] The Relascope is very similar to the angle gauge and the wedge prism in that it can be used to find the basal area of a tree from a point depending on the basal area factor in a variable radius sampling method.

This is done in the same manner as when one uses a transit using a set of trigonometric formulae based on height and angle.

When taking height, users measure either 66 or 120 feet from the tree; this is the reason for the multiple scales in the relascope.

Users then look first at the top of the tree or at the highest point on the bole that they want to measure and record the number from the height dial inside the scope, then they look at the bottom of the tree to find a positive or negative number.