. A primer on stand and forest inventory designs. Forests and forestry Mensuration; Forest surveys. develop a stratified sampling plan. However, the proce- dure might be useful in sampling geo-political divisions- mapped counties within States for example. It might also reasonably be employed where an agency was exploring the forest, such as in large, unmapped tropical areas. Probability Proportional to Size () Sampling—There are several possible estimates of size that might be used to develop a sampling frame. Our example is acreage, but this is really a correlated measure of size. Rece
. A primer on stand and forest inventory designs. Forests and forestry Mensuration; Forest surveys. develop a stratified sampling plan. However, the proce- dure might be useful in sampling geo-political divisions- mapped counties within States for example. It might also reasonably be employed where an agency was exploring the forest, such as in large, unmapped tropical areas. Probability Proportional to Size () Sampling—There are several possible estimates of size that might be used to develop a sampling frame. Our example is acreage, but this is really a correlated measure of size. Recent sampling developments remind us that there should be a strong positive correlation between the measure of size and the actual variate of interest in order for sampling to provide improvements over simple random sampling. This is not strictly the case in the Enchanted Forest data, but for the purpose of this example there should be little loss in efficiency, and the acreage provides a convenient measure of size. When stands are sampled on the basis of proba- bility proportional to their area, several methods of select- ing samples are possible. An intuitively appealing method that yields a sample with probability proportional to area is to place a grid over the forest map. Only those stands in which a grid intersection is located are sampled in the field (fig. 26). Each grid intersection serves as the random Forest Boundary. Figure 26—Location of primary sampling units (shaded stands) and initial O Held Plot secondary sampling units using a superimposed grid. The secondary (Initial) units are located at 60 degrees and 6,203 feet from one another. This provides a selection of stands based upon a probability proportional to their size. 59. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Lund, H. G
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