Multispectral
In remote sensing, multispectral image data refers to data sets that are composed of several spectral channels. The recording is made with so-called multispectral cameras .
Multispectral data therefore contain information about reflected or emitted electromagnetic radiation of different wavelengths . The simplest example of multispectral data is a digital color photograph that contains information about red, green, and blue light. The term multispectral camera is mainly used for sensors that record green, red and near infrared light for scientific purposes. These remote sensing data can also contain mid-infrared and partially thermal-infrared wavelengths.
Examples of remote sensing satellites with multispectral sensors are Landsat , Spot and ASTER . The MKF 6 camera developed in the GDR is best known in German-speaking countries ; further examples are the HRSC and the WAOSS .
Demarcation
Sensors that have a large number of narrow, continuous spectral channels are referred to as hyperspectral sensors ; those that only absorb light of a single wavelength range, as mono - or panchromatic , depending on the width of the range .
Scientific and commercial applications
Due to the increased number of spectral channels compared to conventional digital photography, there are a number of fields of application for multispectral technology in professional photography. If the spectral channels are arranged in a suitable manner in the visible region of the electromagnetic spectrum, the spectra of the recorded objects can be mathematically reconstructed from the sensor signals. This is a great advantage compared to conventional digital photography , which only provides three channels. The appearance of the recorded object under any type of light can be calculated with very high accuracy from the spectra known in each image point. Due to its color fastness, the multispectral recording technology is clearly superior to conventional digital photography.
In astrophotography , direct color images are rarely made, but are increasingly being replaced by multispectral images that are obtained by superimposing filtered sky images in 3 or 4 color areas. In the trichromatic color filters are used in red, green and blue.