The potential of citizen science data to complement satellite and airborne lidar tree height measurements: Lessons from the GLOBE Program

The Global Learning and Observations to Benefit the Environment (GLOBE) Program is an international science, citizen science, and education program through which volunteers in participating countries collect environmental data in support of Earth system science. Using the program's software application, GLOBE Observer (GO), volunteers measure tree height and optional tree circumference, which may support the interpretation of NASA and other space-based satellite data such as tree height data from the Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) and Global Ecosystem Dynamics Investigation instrument. This paper describes tree heights data collected through the GO application and identifies sources of error in data collection. We also illustrate how the ground-based citizen science data collected in the GO application can be used in conjunction with ICESat-2 tree height observations from two locations in the United States: Grand Mesa, Colorado, and Greenbelt, Maryland. Initial analyses indicate that data location accuracy and the scientific relevance of data density should be considered in order to align GLOBE tree height data with satellite-based data collections. These recommendations are intended to inform the improved implementation of citizen science environmental data collection in scientific work and to document a use case of the GLOBE Trees data for the science research community.