Wednesday, 27 April 2011

Trip 4: The first Multi-temporal scanning of conifers using SALCA

The weather on our fourth trip is distinctly more overcast than our previous visits and the air is much cooler. Upon arriving at plot 2, the canopy has changed dramatically in just 1 week:

Phenological Observations - Plot 2:  There is leaf growth on the Birch and Rowan, but this is nothing compared to the Oak trees, which have completed first leaf and some of the trees are almost at full leaf in just one week. The canopy is now significantly covered with foliage. The undergrowth is greening up significantly, with large bracken unfurling and tangles of brambles appearing from autumn's leaf litter.

Fisheye photo at plot 2

The weather is improving as we make our way to site 3 and the sun is rapidly burning away all of the cloud cover.

Phenological Observations - Plot 3: The taller branches of the Sweet Chestnuts are starting to exhibit budburst with most even showing first leaf. The lower canopy consisting of younger trees is significantly more developed with leaves upto 50 mm in length. There is still little undergrowth, with just a few patches of moss appearing from the leaf litter

First leaf at plot 3

Phenological Observations - Plot 4: As expected, the coniferous canopy appears to have changed very little in one week, but the undergrowth has exploded into life. Bracken is the most common species here, growing in tall stalks in the shade, with bushier plants growing where there appears to be more sunlight. The maximum height is 1.3 m.

Setting up times are reducing with increased familiarity and we are currently taking steps towards analysis of the hemispherical fisheye photographs, which will provide a useful comparative result for Gap Fraction Analysis.

I am still very much on the menu as far as the mosquitos are concerned.

Oliver Gunawan
27th April 2011

Tuesday, 19 April 2011

The First multi-spectral scan of an evergreen stand

Delamere Forest, Cheshire, Plots 2, 3 and 4

Another bright and sunny morning has greeted our third field trip and as we are planning to visit all three sites today, our first scan in plot 2 is setup earlier than normal. We are also joined today by Jerry Joy, a Masters student at the University of Salford, who is conducting some research on how differing canopy cover affects GPS signals.

Jerry Joy with differential GPS receiver

Phenological observations - Plot 2: The oak trees are displaying a distinct difference from last week and are well into the first leaf stage of growth. The leaves on the birch trees are also continuing to grow and there is a definite 'greening' of the undergrowth, with a mass of brambles and bracken which are up to about 70cm.

First leaf on lower branch of Oak tree at plot 2

Phenological Observations - Plot 3: There is little phenological change in the larger Sweet Chestnut trees, with a small amount of bud burst visible. On the other hand, smaller Sweet Chestnuts and Rowans approx 3m high are exhibiting a first leaf and are already forming a secondary canopy. There is still very little undergrowth at this plot.

Fisheye photo from plot 4

Plot 4: The final plot is a mixture of Scots Pine and Corsican Pine. This is a predominantly evergreen stand, therefore phenological changes are not obvious in the canopy as new and old needles appear at the same time. This plot is to be used to compare against the deciduous plots and also to test how well SALCA can capture conifer trees in 3 dimensions.

Intensity image from plot 4 using the 1550nm laser

Phenological Observations - Plot 4: The ground is well covered by dead bracken and needle fall and there is a large covering of moss on the ground as well as vigorous bracken growth with immature plants growing up to 80m already.

The future of terrestrial laser scanning, today!

N.B. Mosquito repellent to be added to field equipment list.

Oliver Gunawan
19th April 2011

Tuesday, 12 April 2011

The Second SALCA Field Trip

Delamere Forest, Cheshire, Plots 2 and 3

Rain was forecast in the afternoon of our second field visit, so we only managed to get 2 full scans. However, this has given us an excellent opportunity to visit plot 3 - a stand composed mainly of Sweet Chestnuts, which have not yet completed bud burst, and the odd Rowan tree. A transect has been suggested in each of the plots to measure how the undergrowth develops in relation to canopy cover. Having processed the data from 8th April, we have decided to use the stronger ND1 filter instead of the ND0.6 as the 1550nm laser is still showing signs of saturation and we do not want to lose any more of the signal from the 1040nm.

Rachel Gaulton and Mark Danson with SALCA at plot 3

Phenological Observations - plot 2: The Oak buds in the higher branches are still yet to burst here, however, bud burst has occurred lower down and in younger trees. The Birch trees have already undergone first leaf, but have not yet reached full leaf. The undergrowth is just starting to green up and is mainly composed of bracken starting to unfurl and brambles, with small amounts of moss present.

Fisheye photo from plot 2

Phenological Observations - plot 3: Bud burst has occurred on smaller Sweet Chestnuts, but not yet on the larger trees. The leaves are already out on the Rowans. There is very little undergrowth here, just a small amount of moss.

Fisheye photo from plot 3
The image below displays some of the information we have captured. The fisheye plot shows the intensity of the returned pulses of energy from targets surrounding SALCA. Different substances reflect different amounts of energy and intensity values give us information on how much energy has been reflected from the target. 

Intensity image from plot 3 using the 1550nm laser. Dark blue indicates the highest intensity, whereas brown indicates  lower intensities.
There is still plenty of data to collect and a lot of analysis to complete, but we are really happy with the progress that we have made so far.

Oliver Gunawan
12th April 2011

Friday, 8 April 2011

The First SALCA Trip

Delamere Forest, Cheshire, Plot 2

Just completed the first field measurements with SALCA at Delamere Forest, Cheshire. We selected a mixed Oak/Silver Birch stand (plot 2) that has been used in our previous research with Riegl laser scanners. The main aim was to test the equipment and in particular the new generator, and the filters that we have acquired to try to minimise saturation of some of the close-range waveforms.

It took some time getting ready for this first field trip with plenty of equipment to gather together, including generator, tripod, digital camera, not to mention a host of spirit levels, laptops and cables, this is definitely shaping up to be a 2-person job and one where the off-road pram really comes into its own - despite the funny looks you get from walkers and cyclists in the forest. The set up all worked out in the field and we couldn't have picked a better day for it, with clear blue skies overhead.

Phenological observations: We arrived about a week after bud burst of the birch trees and leaf opening had already started. There are buds on the oaks but the buds have not yet started to open. A recce of the area showed that the sweet chestnut stands were less advanced with only the first signs of bud growth.

Fisheye photo directly above plot 2
We completed two scans at full resolution, which will be compared to hemispherical photos of the canopy. However, the scans took considerably longer than the assumed 'fat-hour' per scan, with full scans completing in about 2 hours, so a low resolution scan was also completed to check the feasibility of this as an option. I will definitely have to bring something to do next time.

SALCA in operation

 We will now have to start the data analysis in order to assess the effects of the different filters and in readiness for the next trip scheduled for next week.

All in all, this was a hugely successful trip: we have collected a lot of data, established our first sampling plot and ensured that the power supply works without any problems.

Oliver Gunawan
8th April 2011

Friday, 1 April 2011

Introduction to the SALCA Diaries

We have just completed a twelve-month NERC-funded project to develop and test a full-waveform multispectral terrestrial laser scanner for characterising vegetation canopies. The project was part of the NERC’s Technology Proof of Concept Scheme and it enabled us to complete the build of the Salford Advanced Laser Canopy Analyser (SALCA), develop software for data analysis and carry out a series of laboratory-based calibration and validation experiments. Professor Philip Lewis and Dr Matt Disney from University College London were project partners and worked on a ray tracing model to simulate SALCA measurements. We have worked closely with Dr Guy Pearson (Halo Photonics Ltd) who built the laser scanner to our design and specifications and he continues to help with R and D aspects of the project.

The Salford Advanced Laser Canopy Analyser (SALCA)

Rachel has now moved to a lectureship at the University of Newcastle where she will continue to work on the SALCA experiments. On 1st April 2011 we started work on a NERC Small Grant project to carry out field trial of SALCA aimed at capturing forest canopy dynamics through weekly measurements in a range of forest stands at Delamere Forest, Cheshire. Oliver Gunawan is now working as an RA on the project and the SALCA diaries are designed to tell you what we are doing, to share the results and provide a forum for discussion. We hope you find it interesting.

Mark Danson and Rachel Gaulton
1 April 2011