You must look into the Suunto while simultaneously sighting along side it to see the tree. Particular care is needed if the operator suffers from astigmatism. A height and range measuring instrument of medium size and weight. It is robust and only moderately expensive. The hand unit contains an angle reading device and a simple computer chip to calculate height above the transponder.
Care is needed on leaning trees .
A transponder attached to a tree bole on a leaning tree will result and a biased estimate of tree height unless the lean is exactly at 90 o to the observer. The Criterion uses laser light to determine distance from a tree. A built in angle reader and a simple computer chip calculates tree height. The LEM uses laser light to determine distance from a tree. A built in angle reader and a simple computer chip calculates tree height.