Panchromatic band

The panchromatic band generally refers to the use of 0.5 micron to 0 Single band of about 75 microns, i.e. visible light band from green to back. The panchromatic remote sensing image is also the image acquisition of panchromatic wave band in the radiation of ground objects. Because it is a single wave band, it is a grayscale image displayed on the map. Panchromatic remote sensing images generally have high spatial resolution, but cannot display the color of ground objects. In practical operation, we often fuse it with multi-band image to obtain the image with both high resolution of panchromatic image and color information of multi-band image.

Multispectral band

Multi-band, also known as multi-spectrum, refers to the absorption of multiple single bands in the radiation of ground objects. The obtained image data will contain spectral information of multiple bands. Color images will be obtained by giving RGB color to different bands. For example, R, G and B are respectively assigned to the spectral information of R, G and B, and the simulated true color image will be obtained. Multi-band remote sensing images can obtain color information of ground objects, but the spatial resolution is low.

Hyperspectral band

Hyper-spectrum, that is, there are many spectra, up to hundreds. The interval between spectra is very small, maybe only a few nm. It contains rich information, which is opposite to multispectral, which generally has only seven or eight bands.

The different performance of different substances under different spectral signals can be drawn into a curve about spectral bands and spectral values. According to the difference of the curve, we can classify different substances in hyperspectral images.

False color

A composite image of any non-R, G, B band. Artificial synthesis is not the original natural color of the object. Pseudo-color synthesis is the most commonly used image synthesis method to improve the display effect of the object type to be determined. The difference from pseudocolor is that the data used in pseudocolor synthesis comes from multiple bands. False color is to enhance the visual effect of color images and make them look more eye-catching.

Multi-band monochrome images are synthesized into pseudo-color images. For example, landsat 7/ETM+has eight bands, and three of them are synthesized into pseudo-color images.

Standard false color synthesis, that is, 4, 3 and 2 bands are respectively given red, green and blue to obtain red image vegetation. Because it highlights the characteristics of vegetation, it is widely used, and is called standard false color.

True color

R. The composite display of G and B bands shows red, green and blue bands 3, 2 and 1 respectively. If the wavelength of the selected wave band in color synthesis is the same or similar to the wavelength of red, green and blue, then the color of the synthesized image will be similar to the true color. This synthesis method is called true color synthesis. The advantage of using true color synthesis is that the color of the synthesized image is closer to the natural color, consistent with the human visual perception of the ground object (target), and easier to recognize the ground object (target).

True color refers to that in each pixel value of a color image, there are three primary color components, R, G, and B. Each primary color component directly determines the primary color intensity of the display device to generate color.

Pseudo-color

The image display only contains one arbitrary band.

The color of each pixel is not directly determined by the value of each primary color component. Instead, the pixel value is used as the entry address of the color look-up table (CLUT) to find the R, G, B intensity values used in the display of an image, and the found R, G, B intensity values are combined to produce color.

Synthesis is a method of converting the gray level of a single-band gray image into color according to a specific mathematical relationship, and then performing color display. Its purpose is to enhance the ability to distinguish ground objects (targets) through the color expression of data.

For example, when passing the security check, the inspection of the package is a pseudo-color display. Its purpose is to highlight the dangerous goods in the package: liquid, knives.

Difference between true color, false color and pseudo-color

1.On the processing object: pseudo-color processing is for grayscale images, and pseudo-color processing is for color images.

2.In terms of processing methods: there are two methods for pseudo-color processing: gray level layering and direct color transformation.

(1) In short, gray level layering is used to layer different gray levels. The number of layers you want to divide is the number of layers, and then forced color is applied on each layer.

(2) The principle of direct color transformation is that any color can be composed of three primary colors, so the gray level of the black and white image is divided into three levels, and each level is given three RGB colors.

False color processing: It is a color image synthesized with multi-band images. Set a certain three bands of the remote sensing image as RGB three primary colors, and then synthesize the color pattern of the image.

Difference: A map of one band is a pseudo-color map, and a map of multiple bands (generally three) may be true color, false color, and standard false color.