Weeds that blight Australian forest floors have a new enemy in the sky: miniature unmanned helicopters.
The CSIRO says the 12kg drones can whiz above the canopy at 5m a second for an hour at a time, capturing about 300 high-resolution images every minute.
The images, which are geo-tagged to within 10m, can then be analysed from the comfort of an office, with specialist weed-killing teams sent in to dispose of the pests.
Because they are so small and nimble, the drones can get to places where manned helicopters, which are conventionally used to spy forest-killing weeds, cannot.
"It's much safer and more convenient," said CSIRO robotics expert Dr Torsten Merz, who has been working on the technology for two years.
With a blade span of 180cm, the petrol-powered drones can fit in the back of a van and can beat the often expensive images captured by orbiting satellites.
Two of the mini helicopters tested near Cairns performed better than expected, Dr Merz said, locating the notoriously invasive "purple plague" shrub Miconia calvescens more thoroughly than manned helicopters.
But the drones face regulatory hurdles before they can be used more widely.
While they are capable of autonomous GPS-based navigation along pre-planned routes and have inbuilt hazard-dodging technology, the Civil Aviation Safety Authority requires all but the most advanced drone operators to keep airborne machines within line of sight.
Given the ruggedness of the terrain and the vast distances involved, that presents a problem, Dr Merz says.
"We require pilotless operations," he said.
"It's a problem because this is something that's not really on the agenda of the aviation authorities."
© AAP 2017