Pilot study using drones and open-source tools to assess Scots pine regeneration in a remote location

This report covers a pilot study funded by eLTER Transnational Access, which aimed to determine the suitability of using drones and an open-source workflow to monitor natural tree regeneration at the Cairngorm ECN site in the Cairngorms National Park, Scotland. The method made use of a consumer grade drone and optical photogrammetry to create a digital surface model (DSM) of each sampling plot. DSMs were then processed through a QGIS workflow to identify and count trees to be compared against ground-truthed data. We find that the method accurately detected c70 % of trees within the plots, and those missed were either small (generally < 50 cm in height) or growing in very close proximity to other trees. We suggest simple measures that could strongly improve the accuracy of detecting smaller trees, and which would result in a practicable, low-cost method for monitoring tree regeneration in mountainous terrain.