Estimating visitor use at attraction sites and trailheads in Yosemite National Park using automated visitor counters

Data on visitor use are essential to the planning and management of National Park units in order to assess visitor impacts to the resource, estimate the quality of the visitor experience, and to inform facilities planning. Recently, automated infrared monitors have become a popular tool to estimate visitor-use levels at attraction sites and along trails in national parks and related protected natural areas. However, there are counting errors associated with all automated counters, thus procedures are required to convert raw counter data to accurate estimates of recreational use. The purpose of this study was to assess the performance (i.e., degree of error) of automated trail traffic counters and document procedures to correct counting errors associated with their use to measure visitor use. This study was conducted in Yosemite National Park in the summer of 2007 and used automated visitor counters to estimate visitor use at attraction sites and trailheads in Yosemite Valley. A total of 135h of direct observation counts were conducted in tandem with the use of automated counters at six study sites to estimate counting errors in the automated counter data. A series of statistical procedures was used to calibrate raw monitor data to accurate estimates of visitor use at each of the study sites. Results of the study suggest there is a strong statistical relationship between observation-based visitor counts and monitor counts (R²>0.95), which supports confidence in the use of monitors to estimate recreational use in national parks and protected natural areas.