LiDAR provides helpful information for felling operations

So how has Forest Research helped foresters assess which machinery will be best for individual operations?

News from Forest Research: July 2008

Digital surface model (top) - Loch Ness appears as the big flat area - and digital terrain model (bottom)Forestry Commission woodland along the banks of Loch Ness above the trunk road between Fort William and Inverness is becoming mature enough to be harvested. For areas such as this, Forest Research has developed a method for detecting individual trees and ground roughness to assist Forest Enterprise plan their felling operations.

It does this by using LiDAR technology which bounces laser pulses from an overhead plane to the area below and back; the range to an object is determined by measuring the time delay between transmission of a pulse and detection of the reflected signal.

The procedure has been used to give planners good information about the location and number of the largest trees, so they are able to plan the harvesting and extraction as effectively as possible.

The procedure followed a series of steps:

  1. Data was processed to filter out the last LiDAR return hits – ie the ones most likely to be ground level rather than canopy
  2. The first returns were processed to create a Digital Surface Model (DSM) - which represents the height of the ground vegetation
  3. The last returns were processed to generate a Digital Terrain Model (DTM). This model was further processed to calculate slope angle and ground roughness which is used to assess which logging machinery is suitable
  4. Finally a routine was developed to map the location of individual trees on the ground and calculate their height directly as the difference between the DSM and DTM.

What's of interest

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This and other news stories can be found in the July 2008 issue of FR Eye, our online newsletter.