Delta-T Devices SunScan SS1 User Manual page 76

Glossary
Beam fraction - the fraction of the Total incident PAR in the Direct beam.
Beam Fraction Sensor - The BF5 consists of an array of 7 photodiodes
under a specially shaped shadow mask, used for measuring Direct and
Diffuse light above the canopy.
Beer's law - a general law describing transmission through an absorbing
medium. The intensity falls off exponentially with distance through the
medium.
Cosine response - the response of a sensor to a ray of light is
proportional to the cosine of the angle of incidence of the ray (measured
from the perpendicular to the sensor surface).
CSV (Comma Separated Variable) a file format intended for importing into
spreadsheet or database programs. Fields are separated by commas, text
is enclosed in quotes. (SunScan use of this file format was discontinued in
2008, when we upgraded SunData to work on Windows Mobile PDAs. We
have replaced this file format with TAB format files, which behaves better
across international regions when imported into spreadsheets.
Data Collection Terminal - the Psion Workabout handheld computer,
previously used for driving the SunScan probe, and presenting and storing
the results, is now superseded by PDAs such as the Nomad, running
Windows Mobile.
Diffuse light - light scattered in the atmosphere. It is treated as coming
from all parts of the sky with equal intensity i.e. a Uniform Overcast Sky.
Direct beam - light coming directly from the sun, with no scattering.
Usually treated as if it comes from a point source.
ELADP - see Leaf Angle Distribution
Emulator - a setting in the SunData software that generates random
results, regardless of whether a SunScan probe is connected. Useful for
learning to use the software.
GMT - Greenwich Mean Time, also called Universal Time (UT). The
standard time used for astronomical measurements and calculations.
Hemispherical response - the response of the sensor is equal for all light
rays coming from above the plane of the sensor surface, independent of
angle.
LAD - see Leaf Angle Distribution.
LAI - see Leaf Area Index.
Leaf absorption - the fraction of intercepted PAR that is actually
absorbed by the leaf. The remainder is reflected or scattered.
Leaf Angle Distribution - a way of describing the distribution of
orientations in space of the canopy elements. We model this using the
Ellipsoidal Leaf Angle Distribution, which describes the distribution of
76  Glossary
SS1 User Manual v3.3