Search

Search Results

• 1. [Article] Probability proportional to size sampling of Douglas-fir from aerial photography

  This experiment was designed to investigate the use of volume estimations from aerial photography and probability proportional to size (PPS) sample selection in the development of a practical sampling design ...

  Citation × Citation Citation Abstract Copy Title: Probability proportional to size sampling of Douglas-fir from aerial photography Author: Rogers, Roger Allan This experiment was designed to investigate the use of volume estimations from aerial photography and probability proportional to size (PPS) sample selection in the development of a practical sampling design for timber volume estimation on small land areas of Pacific Northwest Douglas -fir (Pseudotsuga menziesii, Franco). The major problem of measuring exact stand height to predict stand volume from aerial photos was overcome by the development of two new volume equations which use percent crown closure, visible crown diameter and height classes as the independent variables. By the use of height classes, the photo interpreter is required to separate stand heights as to tall, medium or short. Equations are presented for both board- and cubic-foot volumes. Two computer programs were developed which reduce office calculations to a minimum. The programs compute photo volumes per plot, total gross and net volume estimations per area, standard errors and select the field plots to be sampled. The sampling design was tested on four test areas, using both quarter- and one-acre photo plots, and quarter-acre fixed-area and variable-area field plots at four photo scales. Based on these results a sample of about 20 field measured quarter-acre field plots combined with a 100 percent photo cruise on 1:7,000 aerial photos would be expected to produce gross volume estimations for a forty-acre tract of + 10 percent. at a 68 percent confidence level. Title: Probability proportional to size sampling of Douglas-fir from aerial photography Author: Rogers, Roger Allan This experiment was designed to investigate the use of volume estimations from aerial photography and probability proportional to size (PPS) sample selection in the development of a practical sampling design for timber volume estimation on small land areas of Pacific Northwest Douglas -fir (Pseudotsuga menziesii, Franco). The major problem of measuring exact stand height to predict stand volume from aerial photos was overcome by the development of two new volume equations which use percent crown closure, visible crown diameter and height classes as the independent variables. By the use of height classes, the photo interpreter is required to separate stand heights as to tall, medium or short. Equations are presented for both board- and cubic-foot volumes. Two computer programs were developed which reduce office calculations to a minimum. The programs compute photo volumes per plot, total gross and net volume estimations per area, standard errors and select the field plots to be sampled. The sampling design was tested on four test areas, using both quarter- and one-acre photo plots, and quarter-acre fixed-area and variable-area field plots at four photo scales. Based on these results a sample of about 20 field measured quarter-acre field plots combined with a 100 percent photo cruise on 1:7,000 aerial photos would be expected to produce gross volume estimations for a forty-acre tract of + 10 percent. at a 68 percent confidence level. Close