The issue

CSIRO's initial idea was to develop an improved instrument for scanning the forest top from a low-flying aircraft.

However, after discussions with industry, it was decided that an advanced ground-based lidar (the light equivalent of radar), which can provide much more detail of forest structure than air-borne instruments, would offer greater benefits to the industry.

What CSIRO did

The prototype ECHIDNA™ has motorised controls that rotate it on its tripod, allowing the entire hemisphere above to be scanned.

A separately rotating mirror scans an arc of constant azimuth while the laser fires its pulses.

The receiver telescope collects the returned light waves, and the digitised data is stored in memory before being dumped to disk.

Scanning, laser firing and recording are all under computer control.

The whole system is powered in the field using a small generator, although a commercial version would run on batteries.

Funded by the Forest and Wood Products Research and Development (R&D) Corporation, trials of the prototype have been conducted successfully in:

• plantations of shining gum in Tasmania
• blackbutt and flooded gum on the NSW north coast.

Further trials are planned in:

• radiata pine forests near Mount Gambier in South Australia
• native forests near Tumbarumba, NSW.

The outcomes

Positioned on the forest floor, the lidar-based system – which works on the principle of radar but uses laser radiation instead of microwaves – measures over a radius of 100 metres or more:

• tree basal area
• stem taper
• canopy height
• canopy foliage distribution
• leaf area index
• leaf angle distribution.

‘The combination of a broad beam scan and digitising the entire waveform of the returning pulse makes the instrument unique,’ says one of the system's developers, Dr Darius Culvenor.

‘The validation work will continue until early next year but the results obtained so far are consistent with theory and are very promising.’

Further research

The possibility of developing an airborne version of ECHIDNA™ is also under consideration.

In the meantime, the research team is investigating options for a more portable, user-friendly ground-based version that will deliver interpreted data, such as basal area and canopy height, direct to the user.

CSIRO is confident that much smaller and lighter versions, as portable as survey instruments, will be available once ECHIDNA™ is fully proved and commercialised.

The potential of lidar technology to provide valuable data for forest inventory and management has been recognised for some time.

About the researchers

The Project Scientists were:

• Dr David Jupp
• Dr Jenny Lovell
• Dr Glenn Newnham
• Dr Darius Culvenor