Design and Verification of a Low-Cost Multispectral Camera for Precision Agriculture Application

Abstract

With the rapid increase of the world population, climate changes, and the slow expansion of cultivated areas, only precision agriculture (PA) can provide enough food or resources. PA requires flexible instruments for measuring the spectral signatures of the crops to understand their conditions. Unfortunately, the high initial costs of multispectral (MS) cameras reduce the implementation of PA in small farms, which constitute a large portion of arable land in Europe and contribute with social bonds, local know-how, and cultural legacy. With the objective to speed up the use of MS imaging, in this article, we present a novel low-cost imaging device consisting of an MS camera with nine bands and a thermal imager, whose price is several times lower than commercially available ones. This article describes the design and the calibration of the imaging device based on the off-the-shelf components: Raspberry Pi, dedicated quad camera kit, thermal core, and multiband optical filters. The spectral reconstruction accuracy has a high average R2 score of 0.986. Finally, images from multiple sensors are aligned using phase-only correlation and dense optical flow, providing a method that can be implemented on all platforms. The presented solution is open source, permitting one to modify and expand the capabilities of the described device and adapt to specific needs. Moreover, the device is flexible as the thermal camera can be removed to reduce the total system cost if its usage is not required. Even if its primary application is PA, the proposed solution can be used for other applications.

Keywords

• Multipassband optical filters
• multispectral (MS) camera
• multispectral image registration
• precision agriculture (PA)
• thermal camera
• unmanned aerial vehicle (UAV)