A digital mapping method for linking high-resolution remote sensing images to individual tree crowns

Remote sensing data provides unique information about the Earth’s surface that can be used to address ecological questions. Linking high-resolution remote sensing data to field-based ecological data requires methods to identify objects of interest directly on georeferenced remote sensing digital images while in the field. Mapping individual trees with a GPS often has location error and is focused on the position of the tree stem rather than the crown, often creating a mismatch between field data and the pixel information. We describe a mapping process that uses a consumer-grade GPS and tablet computer to spatially match individual trees measured in the field directly to a digital image of their crowns taken from above the canopy. This paper outlines the reasons for using digital field mapping and a summary of the equipment and process, with supplemental material providing a detailed field protocol. As more remote sensing data with a resolution capable of resolving individual trees become available, the opportunities to leverage these data for ecological studies grow. We provide guidelines for those wanting to apply imagery to expand the spatial scale and extent of ecological studies.