Delta Electronics SS1-UM-1.05 - Manual (Page 18)

18
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SunScan Tutorial Document code: SS1-UM-1.05
Setting up a measurement session
Working through the menu options
In normal use the SunData software calculates Leaf Area Index ( LAI ) based on
readings from the SunScan probe and from the Beam Fraction Sensor (if fitted).
These calculations also require information about the distribution of leaf angles and
absorption of light by leaves within the canopy and knowledge of the solar angle
calculated from the time of day and local latitude and longitude.
SunScan probe Average PAR within canopy
Beam fraction PAR above canopy
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Ratio of Direct to Total light
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ELADP setting Leaf Angle Distribution Leaf Area Index
Absorption setting Leaf PAR Absorption
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Time and date
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Latitude setting Solar zenith angle
Longitude setting
Before it can make sensible calculations of the Leaf Area Index, SunData needs to
know what values to use for the above settings.
♦
Press Menu , use the
← ← ← ← → → → →
arrow keys to
select the Settings menu, and the
↑↑↑↑↓↓↓↓
keys to highlight Site , and press Enter .
Type in a Name for your present site, and
set the Latitude and Longitude by
pressing Del and typing in the
appropriate values. When everything is
correct, to accept it
♦
Press Menu again, then select Time & Date and press Enter . Now set the local
time and date in the dialog box. You also need to set the appropriate offset from
GMT for your time zone. Set
Local time is GMT to between -12.0 and +13.0
hours. Remember to make allowance for any special seasonal offsets, such as
“Summer Time”, “Daylight Saving”. For example: British Summer Time is
GMT+1, India is GMT+5.5, and USA EST is GMT - 5.0.
♦
Press Enter to accept the settings and return to the Title screen.
Note: The date and time formats can be changed, but for the moment just get the
information correct. To change am to pm, select it, and press
p (or a ).
♦
Use the
← ← ← ← → → → →
arrow keys to set the Absorption to
0.85 . Set the ELADP ( E llipsoidal L eaf A ngle
D istribution P arameter) to 1. Press Enter to accept
these settings.
Later sections in Measurement Options and LAI Theory give explanations and
advice on choosing values for these parameters.
♦
Set the Display format to LAI . Leave the ‘Sample’ and ‘Plot’ names unchanged.
The options for Display ( LAI , PAR and All ) have an important effect on the display
of readings but they also interact with the setting for Ext sensor ( BFS or none ) to
determine the sequence of readings required.