Publisher's Synopsis
Excerpt from Photo Stratification Improves Northwest Timber Volume Estimates
Although stratification may be by either type map or photo sampling, type mapping is not usually undertaken unless the type map itself is an inventory objective, since photo plots, when combined with field plots in a stratified sam pling design, do a better job of stratification at less cost.
Although double sampling for stratification offers the potential for esti mating timber volumes more efficiently than a simple field plot sample, there is no guarantee of success. The inventory forester who wonders how well the method might work for him must be guided primarily by the experience of others who have used it. In particular, he will need to know whether double sampling will result in lower sampling errors than might be obtained by simple field sur veys of equal cost, and if so, how much of a reduction in sampling error he can expect. If he decides to adopt the method, he will need to decide how many strata to identify and what boundaries to give them. In addition, he will need to decide how to allocate the field samples among these strata. The theoretical basis for answering these questions can be found in Cochran Unfortunately, localized reports on the results of practical experience are harder to find. Although a number of inventory organizations in the United States and at least one in Canada use double sampling for stratification, only a few have published results and these are inconsistent (1, 2, 4, Additional reports on field experience with forest inventory applications of double sampling for stratification are needed, particularly for the Pacific Northwest where no such published data are available. To help fill this need.
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