Delta-T Devices SunScan SS1 User Manual page 77

canopy elements as in the same proportions as the surface of an ellipsoid.
Using this model, a wide range of different canopy types can be described
by a single parameter, the Ellipsoidal Leaf Angle Distribution Parameter
(ELADP), which is the ratio of the horizontal to vertical axes of the
ellipsoid. An ELADP much greater than 1 describes a canopy of mostly
horizontal leaves, an ELADP near 0 describes a canopy of mainly vertical
leaves.
Leaf Area Index (LAI) - the surface area of leaf per unit of ground area
(assuming leaves are flat, and including only one side of each leaf).
Instruments like the SunScan cannot differentiate between leaf and stem,
so could more correctly be said to estimate Plant Area Index.
Local time - the time used in your particular time zone. It varies from
GMT by an amount depending on longitude, political boundaries, and any
daylight saving time.
Mean Leaf Angle (also Mean Tip Angle, Mean Inclination Angle) is the
average angle of all the leaf elements relative to the horizontal, weighted
according to area. This can be directly related to ELADP.
PAR - Photosynthetically Active Radiation is visible light of wavelength
400 nm - 700 nm. It is measured in units of μmol.m-2.s-1 (micromoles per
square metre per second) or formerly μE (micro-Einstein). The normal
daylight maximum is a little over 2000 μmol.m-2.s-1 .
PAR mapping - the study of distribution and variation of PAR within and
below a canopy.
PRN a text file format intended for directly printable output.
Spread - a measure of the relative variation in light intensity along the
SunScan probe. It is calculated as the Standard Deviation divided by the
Mean (sometimes called coefficient of variation).
SunData software- the software used to drive the SunScan probe and
calculate and store the results.
SunScan probe - the long light sensitive wand and handle used for light
readings within the canopy.
TAB - a text file format in which data fields are separated by TAB
characters. This file format is easily imported into spreadsheets such as
Excel, and can incorporate different conventions for number and date
formats.
Total PAR - the sum of Direct beam PAR and the Diffuse light PAR.
Transmission fraction - the fraction of incident light that passes through
a given canopy. It can refer to Direct, Diffuse, or Total incident light.
Zenith angle - the angle between the centre of the sun and the point
directly overhead.
Glossary  77
SS1 User Manual v3.3