SALCA at the Manchester Science Festival

Mark Danson gave a series of public demonstrations of SALCA at the Salford Sci-Fest in October - part of the 2014 Manchester Science Festival. More than 2000 people attended the event held at the University's Media City Campus on Salford Quays. The demonstration included experiments to measure the speed of light, videos of SALCA in action, and a live demonstration of the instrument.

Lasers Light up the Forest

Sheffield A-level Geography student working at Delamere

This summer saw Phoebe Cox helping out with fieldwork at Delamere Forest. Phoebe, an A-level Geography student from Sheffield, completed a stand survey with Lucy, measuring tree diameters (dbh) and tree heights at the Beech plot. These data will be used to verify the canopy measurements made from the SALCA instrument providing validation of the height, height to base of live crown and dbh estimates. She also had an introduction to the SALCA instrument and battled through the undergrowth to see how the instrument worked in the pine plot.

The maximum tree height was around 33m

Keynote for Mark Danson

Mark Danson presented an Invited Keynote Talk at the Annual Conference of the Remote Sensing and Photogrammetry Society http://rspsoc2014.co.uk/, hosted by the University of Aberystwyth and Environment Systems, last week. Lucy Walker also presented a paper on SALCA measurement of 4D forest phenology. Both papers were well received and there were around 150 registered delegates. The Abstract of Mark's talk is reproduced below.

Mark Danson delivering Keynote at RSPSoc 2014

Laser spotlight on forest structure

Terrestrial laser scanners (TLS) are set to revolutionise measurement of the three-dimensional structure of vegetation canopies, completely replacing manual measurements or indirect estimates of canopy structure, based on light interception. TLS record millions of range measurements of the canopy and understorey elements, in a rapid and repeatable way, and this information can be used to estimate, amongst other things, tree biomass and canopy leaf area index (LAI), and to accurately reconstruct the complete three-dimensional structure of forest stands. Early attempts to extract quantitative information on vegetation from commercial TLS data soon encountered problems related to difficulty in using the radiometric information contained in the data. In response my team at the University of Salford worked with Halo Photonics Ltd. to develop and test the experimental Salford Advanced Laser Canopy Analyser, or SALCA for short, the world’s first dual-wavelength, full-waveform terrestrial laser scanner specifically designed for measuring forest canopy structure.  SALCA provides a test-bed for better understanding the interaction of lasers with vegetation canopies, and an open-access mode of working allows research partners and collaborators to fully explore the strengths and weaknesses of different data processing and information extraction algorithms. In the presentation I will outline the origins of the SALCA instrument, talk about the trials and tribulations of instrument development, discuss examples of the applications which are now being explored and, by example, highlight the importance and benefits of collaborative working in science. 

Developing a dual-wavelength full-waveform terrestrial laser scanner to characterize forest canopy structure

New publication on SALCA in Agricultural and Forest Meteorology - Open Access - click below to read

Developing a dual-wavelength full-waveform terrestrial laser scanner to characterize forest canopy structure

Destructive sampling of oak LAI at Alice Holt

A team from the Universities of Salford, UCL and Newcastle and Forest Research UK completed the destructive sampling of three 80 year old oak trees at Alice Holt in Surrey.

Following leaf off scanning in March and leaf-on scanning in June the three oaks were felled and all leaves removed by the team and bagged to determine their dry weight. We will estimate tree LAI through measurements of specific leaf area (SLA) on a sample of 800 leaves. More results to follow...but here's a short video to illustrate the approach...on YouTube

TLSIIG at Salford University

TLSIIG Salford 2014 brought together 26 researchers from around the world to discuss the technology and applications of TLS for vegetation studies.

Day 1 started after lunch with a PechKucha-style introduction from each of the groups. In all 13 groups presented their team and outlined their interest in TLS research. ‘Technical Corner’ followed with presentations from Mark Danson on SALCA and Brisbane calibration, Zhan Li on DWEL data processing and software challenges, Kim Calders on the Zeb-1 mobile laser scanner, Steve Hancock with an update on echo detection algorithms, Ian Paynter on the new CBL device, John Armston with an overview of Reigl TLS processing, and Mat Disney on the Riegl processing chain.

Day 2 focussed on progress with the TLSIIG Brisbane 2013 data processing and analysis and introduced some new group members – from UK Forest Research, Finnish Geodetic Institute, Technological University of Tampere, and University of Wageningen. After a lunch time demonstration of the highly portable CBL TLS by University of Massachusetts Boston, and the completely portable ZEB-1 by University of Wageningen , the afternoon break-out sessions focused on identifying key priorities for TLS research.  After a busy day the group was treated to a traditional British curry evening in Manchester city centre.

Day 3 explored the opportunities for funding the work of the group and was supported by the university of Salford Research and Innovation Team. Opportunities in the EU Horizon 2020 programme was a key focus and the discussions generated a wide range of ideas to bid for future funding.  A pleasant sunny evening was spent at Salford Quays where the group had a walking tour of the area and enjoyed some well-earned refreshments.

On Day 4 some of the group visited Salford University’s forest test site at Delamere Forest in Cheshire. Again the CBL team were quickly in action scanning the Salford plots alongside the SALCA measurements being undertaken at the site. Beat manager Richard Topley welcomed the group to Delamere in a Q and A session over sandwiches and coffee, and then most of the group drove south to Alice Holt, in Surrey.

Day 5 started with an introduction to UK Forest Research by Peter Freer-Smith and then Eric Casella talked about how TLS methodologies can overcome limitations in estimating forest canopy gaps from conventional hemispherical photography. The group that took a walking tour (and more CBL scanning) of permanent test plots and three sites where the destructive sampling of individual oak tree is planned for early July. After a final pleasant lunch at a local pub, group members headed for home.

TLSIIG Salford 2014

The Terrestrial Laser Scanner International Interest Group (TLSIIG) meets at the University of Salford next week as part of the ongoing collaboration between groups in the UK, USA, Australia, Finland, Netherlands, and Belgium. Around 25 participants from 11 different research groups will meet to discuss progress on the TLS inter-comparison study in Brisbane in 2013. More later....

SALCA team head for the hills

SALCA headed north of the border into Scotland last week as part of Rachel's Royal Society project to examine forest health using remote sensing measurements. Mark, Rachel and Magdalena Smigaj, PhD student at Newcastle, braved the world-famous Scottish midges (Culicoides impunctatus) to collect SALCA data at five test plots in Aberfoyle Forest near Stirling in the Loch Lomand and the Trossachs National Park. 

Rachel and Magdelena equipped for the midges
SALCA seemed to work but how will the midges affect the point clouds?

The project is focussed on a series of instrumented plots, run by Dr Juan Suarez from UK Forest Research, where Red Band Needle Blight, caused by the pathogen Dothistroma septosporum, has infected Scots pine plantation forestry. There is great concern about the spread of the pathogen to other species and in particular to Scots pine in remnant Caledonian forest areas. We will examine the SALCA data to determine whether the foliage in the infected trees can be identified. The UK Natural Environment Research Council (NERC) will fly an airborne hyperspectral imager, full waveform lidar and thermal scanner over the site in the next few days to support the project.

Aberfoyle Forest and the Trossachs

Leaf-off scanning at Alice Holt

SALCA was scanning at Alice Holt, Surrey, UK, last week. The weather was showery and cold but Mark and Lucy managed to scan an Oak plot that is subject to long-term monitoring by Forest Research, and three additional plots where we will destructively sample three Oak trees in early July for woody biomass and total leaf area. We aim to test the application of SALCA for determining leaf area distributions, and the leaf-on leaf-off scans will allows us to test the use of SALCA's two wavelengths for automatic point cloud classification and separation of leaf hits from wood hits.

Full resolution SALCA scan in Oak plot at Alice Holt

Eric Casella (UK Forest Research) is coordinating the experiment and he has been busy scanning the various plots with a Leica TLS. He scanned the birch tree area below in leaf-off conditions and destructively sampled three of the trees for total woody biomass. This is really the 'gold standard' for biomass validation but the work involved is truly heroic. Cutting the trees down is just the start...

Now the hard work really starts...

SALCA returns to Delamere

SALCA has returned to Delamere Forest in Cheshire to start a year-long field campaign to monitor canopy phenology. Five plots have been located within the forest:

Plot 1: Mixed deciduous (mainly Oak and Silver birch)

Plot 2: Sweet Chestnut

Plot 3: Common Beech

Plot 4: Mixed evergreen coniferous (Corsican pine and Scots pine)

Plot 5: Japanese Larch (deciduous conifer)

Leaf-off measurements are nearly complete - just in time as green buds have already started appearing in the Silver birch. Spring is a busy time in the canopy so Mark and Lucy plan to scan frequently throughout this period to capture the 3D characteristics of development and activity within the canopy. The data collected at Delamere will form a significant part of Lucy's PhD.

SALCA at Plot 1

Following a review of the data we collected in Australia, and preparation for our upcoming field campaigns, we have recently implemented a couple of improvements to the instrument and scanning procedures. This has included introducing new filter combinatons to balance the power of the lasers and swapping the petrol generator (which gave up on our first day at Delamere!) with a 24v battery - this has the added benefits of being quiet and much easier to carry!

Mark at Plot 3

New TLS research at Forest Research

In mid January the SALCA team participated in discussions at Forest Research UK to plan a new TLS experiment to scan leaf-off and leaf-on woodland at Alice Holt, Surrey. The plan is to scan the plots in March and July and then to carry out destructive sampling to measure the wood biomass and total leaf area of a number of Oak trees. We were hosted by Eric Casella and James Morison (Forest Research) and others from University College London, University of Grenoble, France, and Tampere University of Technology (TUT), Finland

L to R. Andy Burt (UCL), Lucy Walker (USalford), Markku Akerblom (TUT), Rachel Gaulton (UNewcastle), Eric Casella (ForestResearch), Mark Danson (USalford), Pasi Raumonen (TUT), Mikko Kaasalainen (TUT), Mat Disney UCL), James Morison (Forest Research), Frank Hetroy (UGrenoble)