Shortwave infrared radiation (SWIR) is an electromagnetic spectrum with wavelengths ranging from 0.8 to 2.5 micrometers, which lies beyond the human eye's perception range. This spectrum range is utilized for identifying various materials and rock types. Objects and materials that are not distinguishable in the visible spectrum can be detected using shortwave infrared.

The SWIR range enables the identification of polymeric objects. The spectral characteristics of all plastic polymers have similar distinctive features in the range from 1 to 2.5 micrometers, which allows them to be consistently differentiated. While the color of polymeric objects is significant in the visible spectrum and strongly affects the ability to identify specific objects, it is irrelevant in the SWIR range. Based on the unique spectral features of polymers in the SWIR range, special polymer indices have been developed. The image illustrates how plastic greenhouses are identified in the SWIR range and plastic index.

Plastic Index (right) compared to images in visible (left) and shortwave infrared (center) ranges

Fig. Plastic Index (right) compared to images from the WorldView-3 satellite in visible (left) and shortwave infrared (center) ranges