Delta SS1-UM-1.05 User Manual download pdf (Page 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

ïï

Ratio of Direct to Total light

ïï

ELADP setting Leaf Angle Distribution Leaf Area Index

Absorption setting Leaf PAR Absorption

ïï

Time and date

üü

ïï

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 (Ellipsoidal Leaf Angle

Distribution Parameter) 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.

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Delta SS1-UM-1.05 User Manual Page 18

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