Tip:
Highlight text to annotate it
X
This article sheds light on the use of calculating the “relative-brightness” of red, green, and blue channels.
This article sheds light on the use of calculating the “relative-brightness” of red, green, and blue channels.
We will be using these same calculations...
This article uses the same methodology to track spring “green-up” in leaves.
This graph shows that the green % calculated from a digital camera can give insight as to when a leaf begins to “green-up” as compared with other techniques.
...another study
Here we see the changes in a deciduous canopy over the year of all three channels.
The spike in red indicates the onset of leaf senesence and leaf fall.
The spike in green reveals canopy “green up” and leaf fall.
While the higher blue values correspond with winter snowfall
This will appear when you open the software.
You will want your tree to have a FULL CANOPY COVER, so you can avoid background pixels
The box will allow you to crop you image using polygons, rectangles, ovals, or freehand. Freehand will be easist for your purposes.
As you begin to crop, try to crop the entire edge of your tree canopy.
If you spend more time than me, you want to capture as many of the leaves as possible.
This image is not a great example because the photo was taken in the evening. You can clearly see a lot of solar reflectance from the sun.
After you have selected your “region of interest,” you can crop the picture.
You may want to clear the outside of your selection for asthetic reasons, though it will not change your data either way.
To obtain the data, select Analyze -> Tools -> Color Histogram
Your mean digital numbers will appear. Digital numbers are not a unit, they are simply a number between 0 and 255 that represents the brightness of each channel
Again, here are your raw digital numbers...