Friday, 8 July 2016

Return to Gabon

So we're back in Gabon, returning after 3 years to scan Yadvinder's GEM plots at Mondah where we previously scanned. And then on to Lopé where we'll revisit 2 previously scanned AfriTRON plots, and then a few more new ones established by Simon for the ESA BIOMASS cal/val campaign. This will be the first time we can look at possible changes over 3 years, against a backdrop of the recent very large El Niño event.

Andy is leading the field campaign, over 6 or 7 weeks, with Matheus, myself, Ewan and Joanna coming in and out over the duration. We've had huge help from ANPN Gabon, via Kath Jeffrey, Lee White, David Lehmann and others in organising permits, kit and logistics. Without them it's safe to say this wouldn't be happening. And they've also organised great local help, Leandre and Hector in particular, who are really helping to make the operation much more efficient.

Day 1 and we had this visitor following us on the road!
No you can't have my lunch.




A 'typical' view of the second GEM plot.
Leandre carrying the Riegl out of the plot. A job for a younger man than me these days!
One of the giants we're here to scan, in the centre of our plot. Photos just don't do these trees justice - this one is 50+ m tall, with the enormous buttressed root system and a canopy that seems to be in the clouds.
One thing we're doing here is testing out our new Geoslam ZEB-Revo handheld scanner, to see what it can do. In particular we want to see how well it can capture the tree trunks and diameter, given its relatively short range, and how quickly we can do plots. First results are very encouraging. I scanned our 1h plot in about 80 minutes, generating 500G of data, which took ~6 hrs to process. But Andy and I were surprised at the level of detail and how well the tree trunks were captured. The snapshots here don't really do the detail justice, but this looks very good indeed. It opens up the possibility of us covering many ha at this level of detail, for trunk diameter and shape, to augment the more detailed Riegl data.
A very small slice through the 1ha ZEB scan of the plot.
I also scanned a single large tree in the corner of the plot, looping around it 3 times. The results from this are also very encouraging indeed. Here's a slice showing the tree with 2 slightly smaller (but still huge!) trees next to it. The white points are a second horizontal slice through the cloud, shown in plan view below.

Scan of single large tree (well, 3 really).
A slice through the trunk of the large tree, at about 4m above the ground, with the other two smaller trees next to it, and the rest of the point cloud in gray around them. The larger tree diameter is around 1m.
So, good progress and some interesting results so far and I'm really looking forward to seeing what we can get from the ZEB in combination with the Riegl. It's hard work doing the high density scanning in this landscape though! ;-)



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