Thursday, 28 April 2016

Winter, summer, ground, air ....

Kim has been working on the airborne lidar data over Wytham, provided by David Coomes and co at Cambridge, and originally collected by NERC ARSF as part of the AIRSAR campaign. The data were collected on 24th June 2014, so leaf on and a year before our ground campaign. The image below shows the airborne lidar data over a ~100m transect across Wytham wood.
NERC ARSF lidar collected over the Wytham site, 2014.
 It's immediately obvious the difficulty that even this dense, high quality airborne lidar sensor has in seeing through the canopy. But this is also a lovely example of the power of lidar to show the vertical structure and density of the canopy the layering, and the range of heights over the ground. Below we see the same airborne data overlain on to the TLS summer (leaf on) data. It's worth emphasising what a good job Kim's done in manually overlaying these datasets to get the agreement we can see.

TLS data (green) collected summer 2015 (leaf on) overlaid on to the 2014 summer ALS data.
 Now we can see: how well the two datasets match up, but also the massive amount of detail that is missed when you look down. Clearly, the trade-off is the time and area you can do this. But what a fantastically rich dataset illustrating the canopy structure. We also have of course the leaf off TLS:
TLS data (red) collected winter 2015/16 (leaf off) overlaid on to the 2014 summer ALS data.
Again, this shows beautifully the profile of the canopy, but also how much more we see in winter than in summer of the upper branches. Unsurprisingly! As far as I'm aware no one's ever collected a dataset quite like this with the detailed TLS, ALS and then the spectral and biophysical data. We're all looking forward to exploring these data in more detail in conjunction with the spectral and spatial analysis with David's group, even radar, and the ground-based trait data collected by Yadvinder. And even the aerial photography is a thing of beauty ;-)
Aerial photograph of the Wytham site, with the lodge visible in the centre and the walkway just visible directly above the lodge towards the edge of the image.

Friday, 15 April 2016

Zebedee arrives


While we were away in Ghana, our new "toy" arrived, the ZEB-REVO hand-held TLS instrument (or Zebedee). I say "toy" because it's not - it's a highly-portable laser scanner, developed by CSIRO in Australia, with much lower power and range than our Riegl but with correspondingly much lower weight, hence the much greater portability. It's designed to be used on mobile platforms - cars, UAVs and the like; the platform in this case being our legs. The idea is that we can use it to augment the Riegl, combining both to provide additional information in environments where we may find it hard to move the Riegl around and/or where the understory causes a lot of occlusion. First tests show it's *very* easy to use, which is a key point. Also, so far I'm impressed with the SLAM software that automatically co-registers all the data into a single point cloud. It seems to work well as long as you capture enough objects & targets that the software can identify in post-processing. I'm really looking forward to getting it out into a real forest environment with the Riegl to start experimenting.
The Ginkgo trees in the UCL quad, done in around 1 minute, with ghost Lewis's everywhere.

A rather more careful and complete scan done by Phil of you know where.
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An animation of a walking down Gower Street, done by Kim. And below, a quick look inside the Dept. from a walk out of the lab and down the stairs.
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And finally .... Ewan's nice picture of two great minds at work. Look, how hard can it be, just switch it off and on again.


Kim's BES prize

We're all very proud of Kim, who was recently announced as the winner of the British Ecological Society Methods in Ecology and Evolution (MEE) RobertMay early career researcher award (see http://www.britishecologicalsociety.org/grants-awards/honours_awards_prizes/prize-for-the-best-paper-by-a-young-author/robert-m-may-prize/). Kim won for his paper "Nondestructive estimates of above-ground biomass using terrestrial laser scanning" (seehttp://onlinelibrary.wiley.com/enhanced/doi/10.1111/2041-210X.12301). The paper was the culmination of Kim's PhD work, and involved many of our long-term collaborators, and it was a key piece of evidence vindicating our approach to using TLS to estimate biomass. Kim's paper received quite a lot of attention when it was published, featuring on the UCL News front page amongst other places (see https://www.ucl.ac.uk/news/news-articles/1114/211114-laser-scanning-weighs-trees), and has already been cited 30 times in less than a year. I'm not surprised, and I've no doubt it will go on to be cited many times, given its groundbreaking demonstration of the maturity of TLS for biomass.