Comparison Between Vegetation Index Obtained by Active and Passive Proximal Sensors

Victor Hugo Rohden Prudente,Lucas Volochen Oldoni,Luiz Almeida,Willyan Ronaldo Becker,Erivelto Mercante,Bruno Bonemberger Da Silva,Jerry Adriani Johann,Carlos Henrique Wachholz De Souza

doi:10.5296/jas.v9i2.18462

Abstract

Proximal sensors have been used to characterize the crop biophysical properties by reflectance values and/or using Vegetation Indices (IV). Our goal with this work is to compare NDVI (Normalized Difference Vegetation Index) spectra-temporal profiles obtained by active (GreenSeeker 505 Handheld) and passive (FieldSpec4 model Standard-Res) proximal sensors to monitor soybeans and beans. It was monitored agricultural fields with soybeans Nidera 5909RG variety and beans Imperador variety, located in the municipality of Cascavel, Parana state, Brazil. The proximal sensors were used to monitor the crop's conditions on different Days After Sowing (DAS). NDVI from FieldSpec4 (NDVI FS) showed a higher correlation with GreenSeeker NDVI (NDVI GS) in the wavelengths of 649 nm and 771 nm for soybeans (rs = 0.9105) and 646 nm and 792 nm for beans (rs = 0.9382). The inter-calibration of NDVI GS values in function of NDVI FS, considering the entire phenological cycle, resulted in RMSE = 0.0520 and dr = 0.8630 for soybeans and RMSE = 0.0636 and dr = 0.8890 for beans. NDVI values showed saturation during the major vegetative development of the crops, interfering in the inter-calibration process. In general, the NDVI GS and NDVI FS were similar in terms of their spectral-temporal pattern. According to our results, the active sensor could be used to crop monitoring, resulting in a lower cost and less climatic interference.

Highlights

Food security is a global concern due to the continued population growth and the stagnant number of food production areas (Harfenmeister, Spengler, & Weltzien, 2019)
The results have shown that it is possible to monitor the soybean and bean with the NDVI from the different sensors with similar results
The NDVI GS and NDVI from FieldSpec4 (NDVI FS) had similar spectro-temporal patterns and were found a strong concordance correlation, around 0.9, between the NDVI from the different sensors from soybean and beans. This indicates the possibility of providing the intercalibrate process, which can be used NDVI from one sensor to estimate the NDVI values to the other sensor

Summary

Introduction

Food security is a global concern due to the continued population growth and the stagnant number of food production areas (Harfenmeister, Spengler, & Weltzien, 2019). In this context, soybean and beans, present in many people's food base, are two of the more important crops related to the food demands. Mainly through spectro-temporal profiles, could be related to the crop biomass, allowing monitoring crop phenological development (Johann, Vieira, Lamparelli, & Duft, 2013). The Vegetation Indexes (VI) are spectro-temporal examples that could be used to express the phenological crop cycle (Almeida et al, 2015; Formaggio & Sanches, 2017; Johann et al, 2016).

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Conclusion