Spectral resolution is the ability of a satellite sensor to detect distinct ranges of wavelengths in the electromagnetic spectrum. Essentially the radiation that the sensors receive from the ground can be detected across various wavelengths, including ultraviolet, visible (red, green, blue), infrared and microwave. Ranges of wavelengths are defined as bands in remotely sensed imagery.
Colour images that are taken with a standard camera will include three bands: red, green and blue. Satellite sensors have the ability to provide images with additional bands, which commonly include near infrared and short-wave infrared. In the case of SAR sensors, they detect radiation in the microwave spectral range.
Satellite sensors that can collect only a few bands, with each band having a larger range of wavelengths, have a lower spectral resolution. For example, with cameras that take black-and-white images, they only include a single band, which generally spans the full visible range (red, green and blue). With cameras that take colour images, they include each of the three individual bands: red, green and blue.
The colour camera, therefore, has a higher spectral resolution than the black-and-white camera. With satellite sensors, they may have the ability to detect very small wavelength ranges. For instance, they may include multiple red, green and blue bands, each with smaller wavelength ranges than a standard camera. The more individual narrow bands that a satellite sensor collects, the higher the spectral resolution of that satellite. Sensors with high spectral resolution can be useful for extracting additional information about ground features.
The type of spectral bands included with an image will affect the available image outputs.