Friday, 27 January 2017

Historic London trees

We've been looking at working a little closer to home recently. Not that tropical forests, ancient woodlands and the like aren't interesting enough, just that in an old city like London, there are some pretty incredible trees. These are tied intimately to the history and development of the city itself. The availability of new data sources, in particular the UK's Environment Agency open sourcing their extensive airborne lidar over urban areas, has led to us thinking about how we can use this.

London has a *lot* of trees, many of them large and spectacular London Planes,  Platanus x hispanica. This is arguably THE iconic London tree, with its mottled bark, huge leaves and (sometimes problematic!) seed pods. They line so many streets, parks and avenues, providing shade, cooling and habitat for birds and insects. They can occasionally take a chunk out of unwary double decker buses too.

We're looking at using the EA lidar data, in conjunction with colleagues at in Liverpool, and the GIS Unit at Kew Gardens, to identify and measure trees across London, and then use our ground-based lidar scanning to assess the size, volume and structure of a range of these. We're interested to see whether we can apply the same methods we do to tropical trees to urban/street trees in London, with their wide range of managed histories and shapes. We'd like to assess the amount of Carbon they store, their structure and how this relates to their environment.

As part of this work, we've started close to home, looking at trees in Camden, in collaboration with the Camden Council tree department. The first tree we've looked it is amazing - not a Plane, but an Ash. It's in the cemetery of St. Pancras Old Church, a very old (C11th) church tucked away behind the very modern and redeveloped Kings Cross. The Church history is interesting in itself, but there's an Ash tree in the yard with a very unusual back story. The railway being built in the mid C19th led to part of the cemetery needing to be excavated. A young Thomas Hardy was (supposedly) put in charge of moving displaced headstones, and placed them around the trunk of an Ash tree by the church. The tree and the headstones are now entwined, leaving a strange and rather haunting growing monument. The tree is struggling a bit, partly due to the unusual roots but also due to footfall around it. We are using our NERC NCEO-funded Riegl and ZEB-REVO lidars to scan the tree to build a detailed 3D model snapshot of it to help the Camden team plan their management in order to preserve this historic tree.
Scanning the "Hardy Tree". The railway line, and the modern world, is behind the wall.
A view of the scan data collected by Phil, of the whole church yard with the Hardy Tree to the front centre.

The tree, with the hedgerow surrounding it.

A closer view of the strange, leaf-like headstones around the trunk of the tree.

And this is how it looks 'for real'. Image: David Edgar.
Phil's path around the churchyard, carrying the ZEB-REVO handheld scanner. The Hardy Tree is the one at the front left of the Church with the loops around it.
Phil did a great job of capturing the tree with the ZEB and Riegl, and is currently processing the Riegl data - first example of a fly-through from those data is below. We will be extracting the 3D model of the tree and looking at the structure in detail, and then revisiting over the coming months to capture it leaf on, and then over time if we can.

Here's an additional animation that Phil produced, showing his walk through the church yard, alongside the ZEB data.

And here's the Sketchfab interactive model:


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