Delta-T Devices SunScan SS1 User Manual page 38

Setting ELADP
The default setting of 1.0 (spherical leaf angle distribution) is a good
starting point.
If you are unable to estimate the ELADP any other way, set ELADP to 1.0.
You can check how much this affects your results in the field by making
several measurements in one place within a canopy using different
ELADP values, and comparing the LAI values calculated.
Estimating ELADP in the field
If the canopy shows a clear predominance of horizontal or vertical leaves,
then choose a small volume of the canopy that is representative. Count
the number of leaves that are at more than 45° from the vertical (i.e.
mostly horizontal), and the number of leaves that are less than 45° from
the vertical. If the leaves are curved, pick the angle at the widest part of
the leaf. The ELADP can be estimated as the number of horizontal leaves
), multiplied by /2 (1.6).
(N ) divided by the number of vertical leaves (N
h v

N

h
ELADP
2
N
v
The factor /2 comes from the fact that the vertical leaves are distributed
about the vertical axis, so for any light ray, some will be seen face-on, and
some edge-on. In effect, the ellipsoidal distribution is being further
approximated as a cylindrical distribution.
If you set ELADP to 1024, and Absorption to 1.0, the LAI calculations will
be equivalent to the simple Beer's law inversion based on black,
horizontal leaves.
38  What to Measure and How
SS1 User Manual v3.3