Making Basic Measurements

Now that you’ve become familiar with the operating principles of the LAI-2200C and the instrument accessories, it is a good idea to make a few sample measurements. Be sure to review the practical considerations in Dealing with Sky Conditions and Canopy Types prior to collecting actual data because the use of improper measurement techniques will result in poor data quality.

Operation: One Sensor, One Control Unit

To try out a basic measurement, you will need one LAI‑2270C Control Unit, and one LAI‑2250 Optical Sensor, then follow Example 1 - One Sensor Measurement without scattering correction. You can do this in an actual canopy, of course, or simulate the canopy in the following manner:

1. Go somewhere with a good view of the sky, and use a 90 degree view cap when making A (above canopy) readings. Keep the sun out of the view.
2. Simulate B (below canopy) readings by aiming the sensor in the same direction as the above reading, but substituting a 45 degree view cap instead.

This will theoretically give you gap fractions of 0.5 for each ring, which will result in a leaf area index (LAI) of about 0.86 and a mean tilt angle (MTA) of 39 degrees (with default settings, and a uniform sky - see Figure 5‑1).

Once you have gotten familiar with a basic measurement, you will want to add scattering corrections. These are described in Dealing with Scattering. To try out a basic measurement with scattering corrections, you will need an actual canopy. Follow Example 2 - One Sensor Measurement with Scattering Correction.

Operation: Two Sensors, One Control Unit

To try out basic two sensor operation (Example 3 - Two Sensor Measurement without scattering correction) you will need one LAI‑2270C Control Unit, and two LAI‑2250 Optical Sensors. The first decision to be made involves how you wish to deal with matching the sensors. The approaches are described in Three Methods for FV2200 Matching. You may also choose to completely ignore the matching issue while you get familiar with two sensor operation. In that case, you will be following the steps for "Match Method 1" as you follow Example 3, since that one allows you to completely ignore all matching while collecting field data.

When you are ready to do actual measurements with two sensors, follow the instructions under Procedure 1.8 - Build a Match File for Two Sensors (Match Method 1). We recommend that you do "Match Method 1" and make a match file for your two sensors. Once that is done, the only time you would then deal with matching is when you import and adjust A records using FV2200 during post-processing (Procedure 3.6 - Interpolating A Records - FV2200).

Scattering correction on data collected with two sensors requires a bit more planning and field work, and you have several options. See the discussion in Protocol Suggestions for Direct Sun.

Importing A Readings from Separate Files (Console)

When A readings are collected autonomously, they need to be imported by the file that holds the B readings before LAI can be computed. This can be done on the control unit (described below) or with the FV2200 software see (Procedure 3.8 - Import A and Adjust A Records - FV2200).

Note: Importing on the console is not recommended if the files are large, or if the two sensors have not been matched

1. If it hasn’t been done already, transfer the records from the wand to the console: Go to MENU > Data > Wand > Download > select wand. Choose Create new file and name the file.
2. Go to MENU > Data > Console and select the file that is to receive the imported records. Select the file that has the B readings.
3. Select Edit from the menu, then select Import Observations.
4. Choose to import A records.
5. Press OK and the file will be recomputed using the imported records.
6. LAI values will recompute automatically and can be viewed at MENU > Data > Console > select file > View Header.

Data Management on the Console

In the following section, you'll learn about ways you can manage data and files on the console.

File Quick View

To view a summary of a file, navigate to Menu > Data > Console > select data file > Quick View. The file header is presented:

Quick View:

Viewing Data on the Console

To view data in a file, go to MENU > Data > Console > select data file > View. The following options are presented:

View Header:

View ANGLES/MASKS:

Displays angles and masks used for each ring.

View CNTCT#/STDDEV:

Displays contact number and Standard Deviation for each ring in the current file.

View AVGTRANS/GAPS:

Shows average transmittance and gap fraction for the current file.

View DISTS/ACFS:

Shows the distance vector (path lengths) and apparent clumping factor for each ring.

View Observations:

Shows values for individual readings. Use the left and right arrow keys to navigate through the list.

Reprocessing Data on the Console

A set of basic data processing features are available on the LAI-2200C Control Unit. Refer to Data Analysis with FV2200 for advanced data processing with the FV2200 software. To edit data that are stored on the control unit, go to MENU > Data > Console > select data file >Edit:

Edit Angles to change the angles (normally, the default values should be used).

Edit Mask to apply a mask to one or more rings. Masked rings are ignored when LAI is computed. The data for masked rings is retained in the file.

Edit Distances to change the default distances. This is useful for measuring isolated canopies (see Example 7 - Isolated Tree for an example).

Edit Transcomp to change how transmittance is computed. See Log Setup for a detailed explanation.

Import Observations to import A records from another file to the current file. This command imports all A records or just the ones that are closest in time to the existing B records in the target file.

Strip Observations to delete all A or B observations from a file.

Additional Data Management Features

Three data management options, in addition to those mentioned above, are available at MENU > Data > Console Data > select data file. These include:

Recompute to recalculate LAI and other variables.

Delete to permanently remove the selected file.

Rename to rename the file.

Connecting to a Computer

The LAI-2200C has a USB connection that can be used to transfer data to a computer.

Plug the USB cable into a USB port on your computer and the LAI‑2270C Control Unit. The LAI-2200C is recognized as a USB mass storage device when it is attached to a computer (PC, Mac, Linux platforms are supported). The LAI‑2270C will not be recognized if it is in Logging Mode or a menu, so be sure to enter the Monitor Mode by pressing EXIT, or just turn off the control unit.

When it appears on your desktop, the name of the LAI-2200C will be LAI unless it has been renamed. Inside the LAI directory, you will find a folder named Data, and inside Data you will find your logged data files.

These files can be manipulated in the normal ways: you can rename them, copy them to your computer (drag-and-drop or cut-and-paste), delete them, and open them with an application (FV2200, a spread sheet, etc.). You can also create other directories on LAI, and move any sort of file to them, but only files within the Data folder will be accessible to the console’s software.

In the root directory of LAI, you may see some files with .bin and .img extensions. The .bin and .img files hold copies of the firmware for the console and wand. Updating console or wand firmware involves downloading new files using the FV2200 "Check for Software updates" (Help > Check for Software updates > Show Wand and Console Information), putting them in the root directory of LAI, and then telling the console to do the update (see Instrument Firmware.

To disconnect the console from the computer, eject it before unplugging it—just as you would with any USB storage device.