456 Trees In 16 Minutes: Putting The Emesent GX1 To Work In Woodland

How much useful forestry data can you collect in a single walk? Our colleague James Pick took the Emesent GX1 into a young broadleaf woodland to find out, and the results speak for themselves.

The capture

James walked about 1.15 km of paths in 16 minutes, carrying the GX1 by hand. That one walk produced 454 million points, colourised using the scanner’s four cameras and processed with SLAM (simultaneous localisation and mapping) in Emesent Aura.

The GX1 has RTK GNSS on board, so the point cloud was tied to the British National Grid without any ground control points.

How the Emesent GX1 data was analysed

• A ground model was built, so every point could be measured as height above ground.
  
• The cloud was sliced at breast height (1.0 to 1.6 m) and a circle fitted to each trunk to calculate diameter at breast height (DBH). The median fit was within about 8 mm.
  
• Anything that didn’t continue upwards as a real stem, such as shrubs, branches and noise, was removed.
  
• Each tree’s height was taken from the canopy directly above it.

The results

• 456 trees individually located, each with a trunk diameter and height
  
• Average diameter of 15 cm, with the largest at 46 cm
  
• Typical height of 11 m, with the tallest at about 18 m
  
• Between 400 and 500 stems per hectare

The same walk mapped 4.3 hectares of canopy. Applying the measured stem density to that area gives an estimate of around 2,000 trees across the site. Trees were measured individually within roughly 10 m of the route, so for a full tree-by-tree inventory you’d walk lines 15 to 20 m apart, which would still take well under an hour here.

Every measurement comes from geometry rather than colour, so it works in shade, in poor light or with no imagery at all. The Emesent GX1 is available from Coptrz, and you can read more about Emesent’s Trimble integration in our earlier post.

FAQs

Can the Emesent GX1 be used for forestry surveys?

Yes. In this test, one 16-minute walk located 456 trees and measured each one’s diameter and height.

Does the Emesent GX1 need ground control points?

No. Its on-board RTK GNSS tied the data to the British National Grid without ground control.

Does the GX1 work in poor light?

Yes. The measurements come from lidar geometry rather than colour, so shade and low light aren’t a problem.

Final thoughts

Want to see it on your own site? Book a demo of the Emesent GX1 with Coptrz.