Managers of cable yarding systems, confronted with inherently high owning and operating costs in a very competitive economic environment, need timely, inexpensive and accurate estimates of yarding production. Yarding time, and thereby production, depend on the location of the turn relative to the landing to which it must be transported. Among the important location attributes of a turn are distance and slope to the landing. For all of the turns on a setting the frequency distributions of these attributes are described by turn location parameters. Among the turn location parameters (TLPs) used by forest engineers are average yarding distance and average yarding slope. The assumptions under which a relatively new class of TLP estimators has been developed are discussed in this paper. Recognition of these assumptions and full appreciation of the limitations thereby imposed on the use of the estimators are essential to judicious application of the methodology. Formulas and procedures are given for calculation of numerical estimates and, in order to clarify and illustrate their use, an example is given.
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