True Color RGB Image

What is it?

True color images are simply photos or digital data that appears to the human eye as "real" colors, i.e. a combination of the additive primary colors of red, green, and blue. When added together in equal amounts, these colors form pure white light. Color images are generally more useful than panchromatic (black and white) images, as the human eye can discriminate many more shades of color than it can shades of grey.

The wavelength range represented by visible color is small; from 0.4-0.7 microns. However, the human eye is optimized for its detection. Wavelengths above and below this range must be measured using instruments capable of detecting electromagnetic radiation that the human eye cannot, such as Landsat or HyMap.

True and false color images: Eastern Sierra conifer forests, California

Dataset: HyMap      Image credit: Brigette Martini, UCSC
Characteristics: 126 band, 3m pixel, north is to the right
Processing Shown: Image on the left is a true-color RGB image of a subset of HyMap imagery showing the densely forested Horseshoe Lake basin located in the eastern Sierra. The image on the right is a false color image of the same region. The image on the right is actually what is called a color-infrared image. Wavelengths of light that we normally assign to green are shifted upwards and assigned instead to red. Now, green forests appear to be red to the human eye. This is not the "true" color of a forest from the human perception; it's a "false" color. Wavelengths normally seen as red in a true color image are instead shifted upwards into the infrared range. The human eye is incapable of detecting infrared light, hence again, this image is a false color image.

What is Remote Sensing?

• Definitions
• Radiation and Matter
• Spectral Signatures
• Classification
• True Color RGB
• Groundtruth
• Accuracy Assessment/Field Validation
• Instruments
   - Passive vs. Active
- Envir. vs. Resource
- Multispectral
- Hyperspectral
- Panchromatic

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