Everything surrounding us, we see, are in their original colour composition. This is called True Colour Composite. For instance, we see vegetations as green, sky as blue, soil as brown, etc. So, False Colour clearly means that objects are not in their original colour composition. Whenever any object will be shown in any colour rather than its actual colour, then this will be a false colour.

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Standard False Colour Composite
Standard False Colour Composite of a LISS III image

In remote sensing, False colour is basically concerned with the analysis of satellite images. It refers to a colour rendering method, where the objects are not shown in their original colour composite, which a photograph (true colour image) would show. It is also called ‘Pseudo Colour’. It is all about the representation of a multispectral image.

The Actual Meaning

A false colour image leaves out the natural colour representation to simplify the identification of features that are not easily understandable. For example, in a satellite image, near infrared band is used to detect vegetation.

Formation

Generally human eye catches the visual part of the spectrum, as it uses three spectral bands (Red, Green, and Blue). These bands are combined to create a false colour image. At least two of these three spectral bands are needed for encoding of the false colour, and many other bands can be combined with it.

Basic Principle of FCC

In the true colour images, the RGB (R-Red, G-Green, B-Blue) spectrum is encoded through the corresponding RGB spectral bands, resulting a RGB to RGB mapping.
Standard False Colour Encoding
Standard False Colour Encoding
But for False Colour Composite, this relationship changes. The usual false colour encoding refers to put a RGB image through the visible spectrum and represent it quite differently, such as "GBR to RGB". The conventional false colour encoding of a satellite image is "NRG (Spectral bands) to RGB (Object's colour)", as it means that Red coloured objects will be encoded through the Near-infrared band, Green coloured objects through the Red bands, and Blue through the Green bands. It is important to note that, Blue spectral band is generally avoided as some objects could not be clearly recognised through this. Thus, this Standard False Colour Composite (SFCC) yields the typical vegetation in red colour.

Uses of False Colour Encoding

Uses of false colour encoding can be majorly observed for satellite imagery. Such as follows:
  • Remote sensing satellites, e.g. Linear Imaging Self-sensing System (LISS), Landsat, etc.
  • Space probes, e.g., Galileo.
  • Space telescopes, e.g., Hubble Space Telescope, etc.
These are some common uses, and there are many more fields, where false colour composite or encoding is used.


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