5.15.3. False Colour Composite (FCC) images

In displaying a colour composite image, basically three primary colours (red, green and blue) are used. When the three primary colours are mixed in various proportions, they can produce different colours in the visible spectrum. As we know that each spectral band in visible part is associated with a colour, so three images taken in three different wavelength regions are superimposed after passing them through three colour filters to obtain a colour composite image. If the colour of an object in the colour composite image may not have any resemblance to its actual colour, the output image is known as a False Colour Composite (FCC).

False Colour Composite images are created by combining three different wavelengths of light into a single image. Each of these wavelengths corresponds to a specific primary colour: red, green, or blue. When these wavelengths are combined, they produce various colours that help highlight specific features in the image. For instance, the Near Infrared (NIR) band might represent red in an FCC image, even though in reality, it does not look red to our eyes. This technique can reveal features that are not easily visible in natural colours.

Imagine a movie editor using different filters to enhance specific aspects of a scene. For example, the editor might change the colour of the grass to bright red to emphasize its health in a garden scene. In this way, even though the grass isn't actually red, this 'false' colour can help viewers quickly identify healthy versus unhealthy areas.

There could be many possible combinations of producing a FCC image, however, a common scheme for displaying a multispectral image is NIR band in red, red band in green, and green band in blue colour.

To create a standard False Colour Composite, specific combinations of spectral bands are often utilized. In the commonly used method, the Near Infrared band is displayed as red, the red band as green, and the green band as blue. This method effectively highlights vegetation because healthy vegetation reflects more infrared light, causing it to appear bright in the FCC image. This technique contrasts features like water and bare soil, which reflect differently in the selected bands.

Think about a chef who needs to cook expertly with just a few ingredients. By choosing different combinations of spices and flavours, the chef can create vibrant dishes. Similarly, a remote sensing analyst selects specific bands to combine, showcasing the landscape’s features in a way that tells a more comprehensive story than what natural colours might convey.

In a FCC, vegetation would appear in different shades of red/orange colour, depending on the types and conditions of the vegetation. These shades of colours help identification of various vegetation types from FCC image. The vegetation types will have high reflectance in the NIR band as compared to the Red band. Clear water will appear as dark-bluish due to higher reflectance in green band. Bare soils, roads and buildings may appear in various shades of blue, yellow or grey, depending on their composition.

Color interpretation of False Colour Composite images is crucial in remote sensing. Vegetation typically appears in shades of red or orange since they reflect more infrared light. Water often shows up dark because it reflects less light in the green band, while soils and built structures can vary greatly in appearance based on their materials. Understanding these color relationships allows analysts to discern different land uses and conditions effectively.

Think of a colorful palette an artist uses to mix paints. Each color tells a different part of the story of a painting. Similarly, in FCC images, each color represents different features of the land. If vegetation is bright red, like a vibrant red flower among the greens in a garden, the analyst can quickly tell where plants are thriving compared to bare soil or water, helping them to interpret the land in a visually impactful way.

False Colour Composite images are widely used for various applications such as land cover classification, vegetation health assessment, and environmental monitoring due to their ability to distinguish important features effectively.

FCC images play a significant role in practical remote sensing applications. They help in identifying land uses, assessing the health of crops and forests, and monitoring changes in landscapes over time. By clearly distinguishing features like vegetation, water, and urban areas, FCC images make it easier for researchers and land managers to make informed decisions regarding environmental management and conservation.

Think of a doctor performing an examination. The doctor uses reports and scans to understand a patient's health. Similarly, environmental scientists leverage FCC images to 'examine' the land, assessing its health and managing resources efficiently. Just like a doctor's observations can lead to treatment plans, the insights drawn from FCC images guide actionable strategies for managing our planet.

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