Establishing representative sample designs with aerial photographic observations

Abstract

Low altitude aerial photography of boaters on the Lower St. Croix Wild and Scenic Riverway was examined for utility in determining representative sample size and distribution. During the summer of 1977 a questionnaire effort on the Lower St. Croix was undertaken to assess Riverway Social Carrying Capacity. Questionnaire distribution was undertaken at both purposive and random sites along the river. Additional spatial user information was obtained from several map question responses. During that same summer over 9600 aerial photographic exposures were taken along the Lower St. Croix. Spatial information from both the questionnaire effort and aerial photographs was analyzed with graphic computer output. Differences between the two data collection formats (photography and questionnaires) were examined. Use of aerial photography to determine accurate sample strategies and optimum sample size was explored. A minimum 34 percent reduction in sample size and subsequent costs would have been possible if photography preceded ground‐based questionnaire distribution. In addition to improved accuracy with time/dollar savings, aerial photographs proved effective in use level and area density determinations.

Key words:

• sampling design
• remote sensing
• aerial photography
• river recreation
• spatial patterns
• Lower St. Croix River