Spectral Characterization of Avocado Persea Americana Mill. Cv. Hass Using Spectrometry and Imagery from the Visible to Near-Infrared Range

Abstract

Remote sensing technologies, such as spectral imaging, have great potential for crop monitoring. Spectral systems measure the energy reflected and emitted by a surface, typically between the visible and near-infrared regions of the electromagnetic spectrum. This paper presents a spectral characterization of avocado (Persea americana Mill. cv. Hass) using spectrophotometry and spectral imaging. The study uses data from four avocado farms, which were collected in situ using spectrometers and GreenSeeker sensors and remotely using satellites such as Landsat 8 and Sentinel 2. The spectral signatures captured by the in situ and remote sensors were compared and subsequently related to vegetation indices. Spectrometry revealed differences between young and mature leaves, particularly in the 480 nm to 650 nm region of the spectrum, which showed color changes in young avocado leaves. The analysis of satellite data highlighted significant differences between Sentinel 2 and Landsat 8 spectral signatures. These differences are likely due to several factors, including collection date, preprocessing, and spatial resolution of the data. Finally, the vegetation indices derived from in situ and satellite measurements displayed different scales. For in situ data, the Normalized Difference Vegetation Index (NDVI) values were around 0.9 for the spectrometers and 0.7 for the GreenSeeker sensors. However, the NDVI values derived from satellite data were around 0.4 for Sentinel 2 and 0.3 for Landsat 8.