By Steve Nix
The user's perspective view is compensated for by the dbh graduations (inch marks get shorter as tree diameter increases) which makes it possible to measure a 40 inch diameter tree with a 25 inch long Biltmore stick. Most commercial scaling sticks are calibrated for using at a distance of 25" from the eye and the stick length can also be used to measure eye to tree distance.
Because of the difficulty maintaining exact distance and keeping the stick in the absolute vertical or horizontal, the stick must be regarded as a fairly crude measuring device. The cruising stick is handy for quick estimates but is not generally used by foresters for generating precise cruise data.