Portable Multispectral Camera for Environmental Monitoring

Introduction. Passive spectral remote sensing techniques have come a long way to become the main source of information on the Earth’s surface and atmosphere. Multispectral and hyperspectral cameras are now produced on a mass scale; however, their wider use is still impeded by high cost. Commercially available affordable complementary metal–oxide semiconductor (CMOS) image sensors provide a suitable basis for the development of low-cost multispectral cameras.

Aim. To design and test a portable multispectral camera intended for environmental monitoring in the field.

Materials and methods. The camera design is based on a single CMOS image sensor. Spectral bands are selected by interchangeable interference filters installed in two gear wheels. The optical system of the camera forms a parallel beam of light before its passing through a filter followed by focusing in the sensor plane. Filter switching is performed by a stepping motor. Its rotation, as well as image acquisition and storage, is controlled by a Raspberry Pi single-board computer. Multispectral images were processed using scripts in the Python language.

Results. The optical design of the newly created camera was tested to assess the size and spectral uniformity of its field of view. In addition, the camera was used to obtain several images of vegetation cover. Further, spatial distributions of two vegetation indices – the normalized difference vegetation index (NDVI) and the green–red vegetation index (GRVI) – were calculated. These distributions allowed areas occupied by vegetation to be successfully detected and coniferous trees to be separated from deciduous ones.

Conclusion. The results obtained have confirmed the feasibility of the proposed optical and mechanical design for remote assessment of the ecological status of vegetation cover.

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