Using False color in ArcGIS

Introduction

This project was looking at controlled burn fields and using false colors to visualize healthy and unhealthy vegetation. This is possible due to the sensor used on the aircraft, which along with the tradition RGB bands it gathers both near-infrared (nIR) and infrared (IR) bands. Visualizing these bands is done by replacing the specific RGB bands with the IR or nIR bands. In the images the red band was replaced with IR or nIR, the green band was replaced with the red band of the visual light spectrum and the blue band was replaced with the green band

The first two figures are the standard RGB photo of a field where a controlled burn took place, figure one will be the before picture and figure 2 will be the after.

Figure 1

Figure 2

The images are slightly different, as the post-burn was taken later in the day (as the fields had to be burned before the next series of images were taken) One will notice a small patch of green in one of the fields as the burn didn't completely burn all the vegetation. This leads to an interesting color splotch in the center of the field when the colors are changed. 

One will also notice the fact that the post-burn image is duller and less colorful as it was again taken later in the day and didn't have as much sun to brighten the image. This will lead to duller color changing when the colors are replaced. This is an important fact to keep in mind when taking IR images, as the light of the day will influence how the image is produced.

Method and Discussion

Taking these images and using the color filtering process stated earlier as IR to appear in the red band, red in the green band and green in the blue band. Seen in figure 3 (pre-burn) and figure 4 (post-burn)

Figure 3

Figure 4

In the images, healthy vegetation appears as red, this is because of healthy vegetation reflects IR strongly, as it is damaging to vegetation. This makes the whole image very pink and red as there is a lot of healthy vegetation.












In the post-burn images, the 5 burned fields appear green due to the color filtering. As it can be easier to see the large green patches in a farmer's field of unhealthy vegetation other than picking out brown patches of plants verse just dirt. There is also a small pink patch in one of the fields, which was touched on earlier. This is just a patch of healthy vegetation that wasn't burned.





The next ability with the camera was to look at the normalized difference vegetation index (NDVI) this measures the plant health. This is considered the classic indicator of plant health, as live green plants absorb solar energy they appear white in the images. Black, in contrast, is the dead/unhealthy vegetation, which can be seen in the 5 burn fields. Figure 5 is the pre-burn and Figure 6 is the post-burn.

Figure 5

Figure 6

Conclusion

Using both these options when viewing farmland can be very beneficial instead of trying to discern unhealthy vegetation from other brown and unhealthy looking things around the vegetation. This can help focus farmers so that they know where they should apply chemicals and other methods to save their unhealthy crops. This can save time and money for farmers as they now don't have to spray the whole field with chemicals and just an affected spot.