Detecting young trees from space

Foresters need to know if young trees have survived their first five years. This usually requires visiting the planting site, but with tens of thousands of hectares planted per year, visiting all sites often proves too expensive. Recent aerial photography cannot help as the young trees are too small to be visible. In searching for a solution researchers hypothesised that even if the trees are too small to see, maybe we could ‘feel’ them using Synthetic Aperture Radar (SAR). A different technique to utilising optical data, SAR provides ‘fuzzy’ data on the presence of objects, their size, orientation and texture. The research found that this was possible and data on whether sites had tree cover or not has been derived for extensive areas of Britain and NFI are working to operationalise the process.