Satellite- or aircraft-borne instruments are able to take images of forests and other land covers, and do so across whole landscapes and regions. The resulting images are more than just photographs: they contain layers of detail about different properties of the forest canopy, for example how foliage reflects different wave-bands of light. These properties, cross-referenced with data gathered on the ground, tell us different aspects about what is going on – and how forests change in space as well as time.
“We’ve been increasingly using this ‘top-down’ approach to the study of forests. In particular, we have been developing uses of a new kind of remote sensor – a type of laser scanning known as lidar – in forest science,” explained Dr Simonson, Research Associate in FECG. “For lidar, think radar, though the technology uses laser light rather than radio waves. Lidar involves the firing of laser pulses at very high frequency (many thousands per second) and detecting the backscatter off different objects. In the context of forests, these objects are tree leaves, branches, under-storey plants and the ground surface. These reflectance signals can be timed to minute precision and, based on the speed of light, the relative heights of these objects can be determined.”
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Lidar images © Will Simonson Cambridge Conservation Initiative