Onion is a high-value crop that is highly susceptible to price fluctuations in the Philippines due to weather conditions, global political situations, and other factors. Accurate mapping and yield monitoring is crucial for managing these fluctuations and ensuring stable supply chains. Unlike multispectral satellite images, hyperspectral images offer higher spectral resolution that enable it to differentiate subtle variations in the spectral signatures of onions compared to other crops. Thus, this study explores the effectiveness of PRISMA hyperspectral imagery for mapping onion fields through two distinct methodologies: K-means unsupervised classification and Linear Spectral Unmixing (LSU). The PRISMA image, captured on February 4, 2024, covers the area of Bongabon, Nueva Ecija, known as the onion capital of the Philippines, and its surrounding municipalities. The Level 2D product was denoised using Minimum Noise Fraction (MNF) by Forward MNF followed by Inverse MNF. The dimensionality of the image was then reduced using Principal Component Analysis (PCA). Three sets of data inputs - PC 1-2, PC 1-4, and 175 PRISMA bands - were classified using K-means. Separately, linear spectral unmixing was performed using four representative spectral signatures for each class - onion, rice, and soil – extracted from denoised PRISMA using known field locations. By comparing the outcomes of these methodologies, this research evaluates their accuracies in delineating the onions, with LSU providing more precise quantification of onion extent. The results highlight the potential of hyperspectral remote sensing in precision farming and in effective mapping and monitoring of onion yields to help mitigate market volatility.
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