Social scientists at the U.S. Geological Survey Fort Collins Science Center partnered with researchers from the University of Washington and Department of the Interior to document the approaches agencies commonly use to estimate visitation and review approaches that are less commonly used. 

Estimating visitation can be a challenging task; it may be straightforward to count visitors to places like museums where every visitor pays an entrance fee, but many public lands and waters are free to visit and have numerous entrance and exit points. Agencies use a variety of different methods to navigate this challenge based on the characteristics and context of different locations. Common methods to estimating visitation across agencies include using sensors that count traffic on roads or trails, direct observation of visitors, visitor surveys, and administrative data such as entrance fees, permits, or trail registers. Often, multiple sources of data are combined to generate the most accurate estimates. 

This report also reviews recent research into new and emerging data and approaches for estimating visitation. Digital mobility data based on locations of mobile devices and geolocated social media are the most studied new source of information on visitation. While these data have underlying biases, they can be effective for measuring visitation when calibrated using on-the-ground counts.