Delta-T Devices SunScan SS1 User Manual page 33

Measuring Leaf Area Without a Beam Fraction
Sensor
This is the most complicated option.
For an overview see Take LAI Readings on pages 17 & 18.
Each LAI reading below the canopy requires a previous Incident reading
and a Beam Fraction reading above the canopy.
If measuring LAI without a Beam Fraction Sensor, SunData ensures you
first measure Beam Fraction at least once. (This provides both the
Incident Total and incident Diffuse radiation readings.)
For second and subsequent readings it is appropriate to just check the
Incident total above the canopy, which is quicker. SunData does not insist
you take more Beam Fraction readings, though you may do so if you wish.
If measuring LAI
without a Beam Fraction Sensor,
SunData ensures you first measure
Beam Fraction at least once.
Measuring Incident Radiation
Hold the probe level above the canopy for this reading.
Measuring Beam fraction
Hold the probe level above the canopy as before, but now cast a small
shadow from greater than 50 cm above the probe to shade 5 to 25cm of
SS1 User Manual v3.3
Read Average
YES
Beam Fraction
measured
already?
NO
What to Measure and How  33