WinSCANOPY: Canopy Structure and Solar Radiation Analysis
Image Analysis for Plant Science
img0
Regent Instruments Inc. since 1991

 

 

WinSCANOPY


For sales informations,
contact us by email

sales@regentinstruments.com

img1  
Analysis Process

This page illustrates the steps that lead to the analysis of an image in WinSCANOPY

1. Load an image
2. Specify the region to analyse
3. Sample identification
4. Analysis validation
5. Data saving

1. Load an image  

Image loading is done in a few mouse clicks (click the disk icon and select the image name from a list). WinSCANOPY then displays the image on screen.

2. Specify the region to analyse  

To analyse an image, you must indicate which region of it is of interest (the hemisphere). This can be done by three methods depending on the information you have about the lens and camera.

a) The easiest method is when you own a lens and camera that have been calibrated by Regent Instruments. In this situation WinSCANOPY reads from our calibration file the necessary parameters to identify the region to analyse, so the only thing you have to do is to click the image. This file indicates to WinSCANOPY where is the centre of the hemisphere, what is the radius that produces a 180 degrees field of view and how to compensate for lens distortions. These parameters can easily be overridden to reduce the field of view at the zenith or the horizon for example.

b) You can also specify the region to analyse interactively by doing the following steps:

1. Move the mouse cursor close to the image center.
2. Click and hold down the mouse button. A large circle with a radius line is drawn over the image. You can adjust the circle diameter by pressing keyboard keys and change its position by moving the mouse.

 
 

3. Centre the circle in the hemisphere area by moving the mouse.
4. When the cursor circle is perfectly synchronized with the hemisphere boundary, release the mouse button.

c) You can also specify the region to analyse numerically by entering the centre position and radius size in pixels. You can determine these parameters experimentally. Although some freeware manufacturers claim this step is "easy", you will have to invest material resources and significant time to do this precisely (the final often cost being larger than buying a complete calibrated system ready to use).

3. Sample identification  

When you release the mouse button after the hemisphere creation, WinSCANOPY automatically displays the sample identification window that allows you to set the information specific to the image being analysed. You can customize this window's information (you choose which information is shown) which includes details about the camera settings, localization, operators, weather, etc... Higher end versions of WinSCANOPY automatically extracts from the image file the camera and lens settings (time, date, exposure, aperture, camera model, firmware version...) that were used to acquire the image (useful to verify if the lens focal length was at the right position) and read GPS data (latitude, longitude and altitude) if such a device was connected to the camera at image acquisition (contact us before purchasing if GPS is important for you). Some of this information is used for the analysis, latitude and longitude are used to calculate solar paths for example, while the rest is simply reproduced in the data files along with the measurements. When you click OK in this identification window, the analysis begins and is displayed after completion.

Once a hemisphere has been created, subsequent images produced with the same camera and lens can be analysed rapidly by activating a menu command. The hemisphere’s diameter and position in the image are also saved in the measurement data file so these parameters can be verified after the analysis. The analysis data and settings are also saved with the image (in the same tiff file) and can be retrieved later by WinSCANOPY for verification or reanalysis.

If you open images that have a different resolutions or aspect ratios than the one used for calibration, WinSCANOPY will automatically scale and reposition the hemisphere so the right area is analysed.

4. Analysis validation  

When the analysis is complete, it is visible in the main window. The sky grid, divided in the number of azimuthal and zenithal divisions that you choose, is displayed in yellow. Messages to the operator and partial analysis data are displayed to the left of the image. More data can be found in WinSCANOPY's data files.

 
 

Additional information about a sky region can be displayed by clicking the sky region in the image.

Suntracks, each containing the sun’s position in the image for different hours of a particular day, are displayed with rainbow-style colors (the color is related to the intensity of the radiation level above the canopy). The summer and winter solstices are also drawn. Dates can be displayed close to the suntracks

When you click a suntrack, information about its closest point to the clicked position will also be displayed. This includes the date, the hour and the instantaneous radiation value for that moment of the day. Its data are also displayed in the graphic above the image and summarized to the left of the image.

Menus in the upper-right corner of the graphic (all versions except Basic) allow you to select the type of data and the relevant options you wish to be displayed. The leftmost pop-up menu contains nine items, each representing a different type of data which can be displayed on the graphic. These data types include:

  1) Radiation level per hour of the day for the active suntrack  
   
  2) Radiation level per day  
   
  3)Gap fractions in function of zenith or azimuthal direction  
   
  4) Leaf angle distribution  
   
  5) Sunfleck frequency distribution (number in function of duration in minutes)  
   
  6) Sunfleck duration (total in minutes) per day of the growing season  
   
  7) Gaps size cumulative distribution  
   
  8) Leaf projection coefficient in function of zenith angle  
   
  9) Clumping index in function of zenith angle  
   
5. Data saving  

At the end of the analysis, data are automatically saved by WinSCANOPY in standard ASCII text format that is well adapted to manipulation into spreadsheet-style programs like Microsoft Excel. You have entire control on what is saved in data files. You can choose to save or not:

  1. Title lines that indicate each columns content
  2. The settings used to analyse the image (all parameters entered by the operator, if the image has been edited or filtered before analysis), information about the camera, lens, image (size, name...) and the analysed hemisphere position and size to name a few
  3. The measurement data (LAI, Openness, Radiations...).

Data produced by WinSCANOPY fall into these categories (the list below is incomplete):

  • Global data. These are measurements that have a single value for the entire image. Some examples of global data are the site factors, openness, daily radiation for the growing season and leaf area index. WinSCANOPY's analysis settings are also saved in the global data line along with the image information (file name, photo #, date, location,...).
  • Gap fractions per sky region, per elevation ring and per direction. Openness per elevation ring.
  • Radiation per day. This include six data types: direct and indirect (diffuse), above and below canopy and total radiation. These are output values for the sun position interval chosen by the operator (every three minutes for example) and a total values for the day. Radiation is clearly presented by day and month (10 June 2000) rather than by Julian or decimal days (like day 322).
  • Leaf angle density and cumulative leaf angle density.
  • A table of the percentage of time that direct radiation is received at the photo location; per hour for each month.
  • Sunfleck distribution and duration.
  • Clumping index in function of zenith angle and per sky region.
  • Leaf projection coefficient in function of zenith angle.
  • Measured and theoretical gaps size distribution.