IP and LAI-2200 are
y Coops et al., (2004),
DHP and LAI-2000
ear regression with an
lies may be explained
ements, measurement
ng software to derive
in the Coops et al,
s and the Eucalyptus
nificantly taller and
) the species found in
I values reported in
1 the study area in
er biomass of the tree
et al., (2004) also
this study compared
ot. Lastly, different
JAI from DHP in the
emiView 2.1 software
efine a threshold for
sky elements for gap
software used in this
a
ve
Rushworth
an increased coverage
ing the measurement
iparison of results at a
s (Nelder, 1962). The
t level of a variety of
o be undertaken at a
leasurements.
1al point scale will be
metrics for both the
| same metrics from
stermining the degree
fferent metrics will be
mine the degree of
the ratio of woody to
. will enable the ratio
calculated. This ratio
ink between LAI and
nents for comparison
with each other over
s each instrument has
- example, FCOVER
is derived over a FOV,
gregated of the same
FCOVER can be
and then compared to
for testing of various
os, will enable the
minimum number of measurements and their location to be
determined in order to characterise the variability of each
metric for the entire plot. This will provide insight as to the
approximate sampling scheme required for each plot location
as each site is relatively homogenous.
A further comparison will be made between the height profile
from the modified FPC and the bottom of canopy returns from
the TLS data. The dense TLS dataset will provide a reference
dataset for the modified FPC measurements and give an
indication of the robustness of the FPC sample density.
An investigation will be conducted io determine whether a
more accurate extent of the individual FOV point measurement
from the passive sensors can be derived from TLS. The
restricted FOV from each passive instrument will be projected
out from the centre of the TLS point cloud to determine a
theoretical extent of the sampling radius. The restricted FOV
will be 115 degrees, as the 57.5 degrees azimuth angle was
found to be favourable to derive LAI (Wilson, 1963). Once the
approximate sample radius is calculated, it will be utilised as a
more geometrically accurate sample size at each point
measurement for validation and calibration of aerial and
satellite remote sensing datasets.
2.5 Future Planned Research
As Project 2.07 is still in the first year of a three year study, the
majority of the research is yet to be conducted. The two study
areas that are the focus of this future research are Rushworth
and Watts Creek. Both areas provide for a good comparison as
the vegetation species and distribution are different, as well as
climatic factors. Below is an outline of a subset of future
planned activates, intended research and preliminary
methodology.
Airborne data collection: Aerial data consisting of ALS and
imagery will be acquired at the 5x5km extent for each site. The
ALS scanner to be flown is a Riegl LMS Q560. The
approximate flying height is 1km and a ground sample density
of 20 points/m^. The absolute horizontal and vertical accuracies
expected are +0.3m and +0.2m respectively. The ASIA Eagle
and Hawk passive scanners are to be flown to provide a
seamless high spatial resolution (<Im pixel size) dataset
(NERC, 2012). The sensors provide radiometric resolution
from 400nm to 2500nm.
Study Area Scale Characterisation: A major aim is to collect
the in situ data for scaling to aerial and satellite remotely
sensed datasets. The in situ data will be utilised for both
calibration and validation of the aerial imagery and LiDAR
captured for Project 2.07. The site sampling scheme is pivotal
fo ensure the in situ data will provide a robust scaling method.
The centre 3x3km of the site is to be stratified into nine 1km
grids, each with one randomly selected plot location. The
sampling design for each plot will follow the SLATS Star
Transect protocol (TERN, 2012). The design consists of three
100m long transects centred at the middle of the plot (Figure 4).
The first transect is aligned in the North-South direction, where
the next two transects are placed at 60? rotations from the
centre point.
For each of the three 100m transects, an LAI value is recorded
at every meter interval using the LAI-2200, totalling 300
measurements. The DHP and CI-110 capture one image at the
centre of the plot, one image at each point 25m away from the
centre, and one image at the end of each arm, totalling 13
images from each instrument. The TLS is to complete one scan
at the centre point. However, due to logistical constraints the
TLS will be utilised at only a subset of the nine plots for each
site.
s
a
Figure 4: SLATS Star Transect Sample Design.
240°
180*
The in situ measurements will be related to the passive aerial
datasets though transfer functions (Zheng & Moskal, 2009).
Transfer functions enable the metric to be derived at the scale
of the data captured by remote sensing instrument. ALS can
derive gap fraction through ratios of below canopy returns to
total returns (Morsdorf ef al., 2006). A future aim is to compare
the LAI derived dataset at the site scale against the MODIS
LAI product. Furthermore, the MODIS product could be
validated from the in situ measurements collected from this
research.
3. CONCLUSION
LAI and canopy cover are important for forest managers and
decision making. This paper outlined a comparison between
two passive terrestrial remote sensing technologies used to
derive LAI metrics. The area investigated contained dry
sclerophyll forest is representative of vegetation found in
Victorian land systems. Preliminary results indicated a poor
correlation between two passive instruments for deriving LAI.
Future research will be conducted to examine the differences in
instruments and methods, and include other active and passive
terrestrial sensors for comparison. The in situ data can be
utilised for both calibration and validation of the coincident
aerial imagery and LiDAR.
4. REFERENCES
Baret, F., Hagolle, O., Geiger, B., Bicheron, P., Miras, B., Huc,
M. et al (2007). LAI, fAPAR and fCover
CYCLOPES global products derived from
VEGETATION. Part 1: Principles of the algorithm.
Remote Sensing of Environment, 110(3), 275-286.
Caldas, L. S., Luttge, U., Franco, A. C., & Haridasan, M.
(1997). Leaf heliotropism in Pterodon pubescens, a