What is false-colour processing?
While our eyes only detect a fraction of all light available, satellite sensors can actually capture – and send back – much more information. Furthermore, this information is relayed back to us in a format quite different from the photographs we are used to. For each band, satellites capture the spectral reflectance of the area within a specific narrow band of the light spectrum.
True-colour composite images use the red, green, and blue bands gathered by satellites to mimic the range of vision for the human eye, showing us images closer to what we would expect to see in a normal photograph.
Satellites also capture information in the non-visible part of the light spectrum. Different features: rock, bare soil, vegetation, burned ground, snow, sediment-rich water, etc. all have different reflectance properties in each band. This a called a 'spectral signature'.
To highlight specific features, one or more of the RGB bands can be substituted for another, such as infrared, or near infrared, which are not visible to the human eye. These images are referred to as false-colour images.
Additionally, to better discriminate between features and highlight changes in time, mathematical models can be applied to the data to produce a new kind of processed image. These are referred to as indexes.
When should I use false-colour infrared?
False-colour infrared processed images are created using the following bands : Near infrared (NIR), red, and green. In the processed images, the NIR band will be colorized red, the red band colorized green, and the green band colorized blue.
Tracking vegetation health
When looking at false-colour infrared images, you will notice that vegetation appears bright red in the image, instead of the usual green.
Since chlorophyll, which can be found in higher concentration in healthy vegetation has a really high reflectance in the NIR spectrum, displayed as red in the images, healthier vegetation will appear in a very vibrant red. Stressed vegetation will be in a subdued shade of red.
By contrast, fallow fields would appear in blue and white colors. In this band combination, cities and exposed ground will be often displayed as gray or tan, and clear water is often black (as it absorbs all three bands displayed).
Looking at minerals
Near-infrared data can also help identify types of rock and soil. Exposed rocks can be shown as brown, gray, yellow, and blue. Rock variations in colors mainly reflect the presence of iron minerals and variations in albedo (solar energy reflected off the surface).
How to obtain false-colour infrared data using EarthCache
Note: If you do not have an account, you can sign up for one here.
To obtain a true-colour image using EarthCache, simply select False-colour infrared processing as an output when creating or editing a pipeline through the dashboard.
To obtain a true-colour image using code, you can create or edit a pipeline using the following parameters:
False-colour infrared ID