A method for reflectance index wavelength selection from moisture-controlled soil and crop residue samples

A. Hamidisepehr; M. P. Sama; A. P. Turner; O. O. Wendroth

doi:10.13031/trans.12172

A method for reflectance index wavelength selection from moisture-controlled soil and crop residue samples

A. Hamidisepehr, M. P. Sama, A. P. Turner, O. O. Wendroth

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11 Scopus citations

Abstract

Reflectance indices are a method for reducing the dimensionality of spectral measurements used to quantify material properties. Choosing the optimal wavelengths for developing an index based on a given material and property of interest is made difficult by the large number of wavelengths typically available to choose from and the lack of homogeneity when remotely sensing agricultural materials. This study aimed to determine the feasibility of using a low-cost method for sensing the moisture content of background materials in traditional crop remote sensing. Moisture-controlled soil and wheat stalk residue samples were measured at varying heights using a reflectance probe connected to visible and near-infrared spectrometers. A program was written that used reflectance data to determine the optimal pair of narrowband wavelengths to calculate a normalized difference water index (NDWI). Wavelengths were selected to maximize the slope of the linear index function (i.e., sensitivity to moisture) and either maximize the coefficient of determination (R²) or minimize the root mean squared error (RMSE) of the index. Results showed that wavelengths centered near 1300 nm and 1500 nm, within the range of 400 to 1700 nm, produced the best index for individual samples. Probe height above samples and moisture content were examined for statistical significance using the selected wavelengths. The effect of moisture was significant for both bare soil and wheat stalks, but probe height was only significant for wheat stalk samples. The index, when applied to all samples, performed well for soil samples but poorly for wheat stalk samples. Index calculations from soil reflectance measurements were highly linear (R² > 0.95) and exhibited small variability between samples at a given moisture content, regardless of probe height. Index calculations from wheat stalk reflectance measurements were highly variable, which limited the usefulness of the index for this material. Based on these results, it is expected that crop residues, such as wheat stalks, will reduce the accuracy of remotely sensed soil surface moisture measurements.

Original language	English
Pages (from-to)	1479-1487
Number of pages	9
Journal	Transactions of the ASABE
Volume	60
Issue number	5
DOIs	https://doi.org/10.13031/trans.12172
State	Published - 2017

Bibliographical note

Funding Information:
This is Publication No. 17-05-083 of the Kentucky Agricultural Experiment Station and is published with the approval of the director. This work is supported in part by the USDA National Institute of Food and Agriculture, Multi-state Project S1069. This work is supported in part by the National Science Foundation under Grant No. 1539070, Collaboration Leading Operational UAS Development for Meteorology and Atmospheric Physics (CLOUD-MAP), to Oklahoma State University in partnership with the University of Oklahoma, the University of Nebraska-Lincoln, and the University of Kentucky. Special thanks to Jason Walton of the Department of Plant and Soil Sciences at the University of Kentucky for his help with preparing soil samples and collecting the wheat stalk residue used in this study.

Funding Information:
This is Publication No. 17-05-083 of the Kentucky Agricultural Experiment Station and is published with the approval of the director. This work is supported in part by the USDA National Institute of Food and Agriculture, Multistate Project S1069. This work is supported in part by the National Science Foundation under Grant No. 1539070, Collaboration Leading Operational UAS Development for Meteorology and Atmospheric Physics (CLOUD-MAP), to Oklahoma State University in partnership with the University of Oklahoma, the University of Nebraska-Lincoln, and the University of Kentucky. Special thanks to Jason Walton of the Department of Plant and Soil Sciences at the University of Kentucky for his help with preparing soil samples and collecting the wheat stalk residue used in this study.

Publisher Copyright:
© 2017 American Society of Agricultural and Biological Engineers.

Keywords

Near-infrared reflectance
Normalized difference water index
Remote sensing
Soil moisture
Spectroscopy

ASJC Scopus subject areas

Forestry
Food Science
Biomedical Engineering
Agronomy and Crop Science
Soil Science

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10.13031/trans.12172

Cite this

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title = "A method for reflectance index wavelength selection from moisture-controlled soil and crop residue samples",

abstract = "Reflectance indices are a method for reducing the dimensionality of spectral measurements used to quantify material properties. Choosing the optimal wavelengths for developing an index based on a given material and property of interest is made difficult by the large number of wavelengths typically available to choose from and the lack of homogeneity when remotely sensing agricultural materials. This study aimed to determine the feasibility of using a low-cost method for sensing the moisture content of background materials in traditional crop remote sensing. Moisture-controlled soil and wheat stalk residue samples were measured at varying heights using a reflectance probe connected to visible and near-infrared spectrometers. A program was written that used reflectance data to determine the optimal pair of narrowband wavelengths to calculate a normalized difference water index (NDWI). Wavelengths were selected to maximize the slope of the linear index function (i.e., sensitivity to moisture) and either maximize the coefficient of determination (R2) or minimize the root mean squared error (RMSE) of the index. Results showed that wavelengths centered near 1300 nm and 1500 nm, within the range of 400 to 1700 nm, produced the best index for individual samples. Probe height above samples and moisture content were examined for statistical significance using the selected wavelengths. The effect of moisture was significant for both bare soil and wheat stalks, but probe height was only significant for wheat stalk samples. The index, when applied to all samples, performed well for soil samples but poorly for wheat stalk samples. Index calculations from soil reflectance measurements were highly linear (R2 > 0.95) and exhibited small variability between samples at a given moisture content, regardless of probe height. Index calculations from wheat stalk reflectance measurements were highly variable, which limited the usefulness of the index for this material. Based on these results, it is expected that crop residues, such as wheat stalks, will reduce the accuracy of remotely sensed soil surface moisture measurements.",

keywords = "Near-infrared reflectance, Normalized difference water index, Remote sensing, Soil moisture, Spectroscopy",

author = "A. Hamidisepehr and Sama, {M. P.} and Turner, {A. P.} and Wendroth, {O. O.}",

note = "Funding Information: This is Publication No. 17-05-083 of the Kentucky Agricultural Experiment Station and is published with the approval of the director. This work is supported in part by the USDA National Institute of Food and Agriculture, Multi-state Project S1069. This work is supported in part by the National Science Foundation under Grant No. 1539070, Collaboration Leading Operational UAS Development for Meteorology and Atmospheric Physics (CLOUD-MAP), to Oklahoma State University in partnership with the University of Oklahoma, the University of Nebraska-Lincoln, and the University of Kentucky. Special thanks to Jason Walton of the Department of Plant and Soil Sciences at the University of Kentucky for his help with preparing soil samples and collecting the wheat stalk residue used in this study. Funding Information: This is Publication No. 17-05-083 of the Kentucky Agricultural Experiment Station and is published with the approval of the director. This work is supported in part by the USDA National Institute of Food and Agriculture, Multistate Project S1069. This work is supported in part by the National Science Foundation under Grant No. 1539070, Collaboration Leading Operational UAS Development for Meteorology and Atmospheric Physics (CLOUD-MAP), to Oklahoma State University in partnership with the University of Oklahoma, the University of Nebraska-Lincoln, and the University of Kentucky. Special thanks to Jason Walton of the Department of Plant and Soil Sciences at the University of Kentucky for his help with preparing soil samples and collecting the wheat stalk residue used in this study. Publisher Copyright: {\textcopyright} 2017 American Society of Agricultural and Biological Engineers.",

year = "2017",

doi = "10.13031/trans.12172",

language = "English",

volume = "60",

pages = "1479--1487",

number = "5",

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T1 - A method for reflectance index wavelength selection from moisture-controlled soil and crop residue samples

AU - Hamidisepehr, A.

AU - Sama, M. P.

AU - Turner, A. P.

AU - Wendroth, O. O.

N1 - Funding Information: This is Publication No. 17-05-083 of the Kentucky Agricultural Experiment Station and is published with the approval of the director. This work is supported in part by the USDA National Institute of Food and Agriculture, Multi-state Project S1069. This work is supported in part by the National Science Foundation under Grant No. 1539070, Collaboration Leading Operational UAS Development for Meteorology and Atmospheric Physics (CLOUD-MAP), to Oklahoma State University in partnership with the University of Oklahoma, the University of Nebraska-Lincoln, and the University of Kentucky. Special thanks to Jason Walton of the Department of Plant and Soil Sciences at the University of Kentucky for his help with preparing soil samples and collecting the wheat stalk residue used in this study. Funding Information: This is Publication No. 17-05-083 of the Kentucky Agricultural Experiment Station and is published with the approval of the director. This work is supported in part by the USDA National Institute of Food and Agriculture, Multistate Project S1069. This work is supported in part by the National Science Foundation under Grant No. 1539070, Collaboration Leading Operational UAS Development for Meteorology and Atmospheric Physics (CLOUD-MAP), to Oklahoma State University in partnership with the University of Oklahoma, the University of Nebraska-Lincoln, and the University of Kentucky. Special thanks to Jason Walton of the Department of Plant and Soil Sciences at the University of Kentucky for his help with preparing soil samples and collecting the wheat stalk residue used in this study. Publisher Copyright: © 2017 American Society of Agricultural and Biological Engineers.

PY - 2017

Y1 - 2017

N2 - Reflectance indices are a method for reducing the dimensionality of spectral measurements used to quantify material properties. Choosing the optimal wavelengths for developing an index based on a given material and property of interest is made difficult by the large number of wavelengths typically available to choose from and the lack of homogeneity when remotely sensing agricultural materials. This study aimed to determine the feasibility of using a low-cost method for sensing the moisture content of background materials in traditional crop remote sensing. Moisture-controlled soil and wheat stalk residue samples were measured at varying heights using a reflectance probe connected to visible and near-infrared spectrometers. A program was written that used reflectance data to determine the optimal pair of narrowband wavelengths to calculate a normalized difference water index (NDWI). Wavelengths were selected to maximize the slope of the linear index function (i.e., sensitivity to moisture) and either maximize the coefficient of determination (R2) or minimize the root mean squared error (RMSE) of the index. Results showed that wavelengths centered near 1300 nm and 1500 nm, within the range of 400 to 1700 nm, produced the best index for individual samples. Probe height above samples and moisture content were examined for statistical significance using the selected wavelengths. The effect of moisture was significant for both bare soil and wheat stalks, but probe height was only significant for wheat stalk samples. The index, when applied to all samples, performed well for soil samples but poorly for wheat stalk samples. Index calculations from soil reflectance measurements were highly linear (R2 > 0.95) and exhibited small variability between samples at a given moisture content, regardless of probe height. Index calculations from wheat stalk reflectance measurements were highly variable, which limited the usefulness of the index for this material. Based on these results, it is expected that crop residues, such as wheat stalks, will reduce the accuracy of remotely sensed soil surface moisture measurements.

AB - Reflectance indices are a method for reducing the dimensionality of spectral measurements used to quantify material properties. Choosing the optimal wavelengths for developing an index based on a given material and property of interest is made difficult by the large number of wavelengths typically available to choose from and the lack of homogeneity when remotely sensing agricultural materials. This study aimed to determine the feasibility of using a low-cost method for sensing the moisture content of background materials in traditional crop remote sensing. Moisture-controlled soil and wheat stalk residue samples were measured at varying heights using a reflectance probe connected to visible and near-infrared spectrometers. A program was written that used reflectance data to determine the optimal pair of narrowband wavelengths to calculate a normalized difference water index (NDWI). Wavelengths were selected to maximize the slope of the linear index function (i.e., sensitivity to moisture) and either maximize the coefficient of determination (R2) or minimize the root mean squared error (RMSE) of the index. Results showed that wavelengths centered near 1300 nm and 1500 nm, within the range of 400 to 1700 nm, produced the best index for individual samples. Probe height above samples and moisture content were examined for statistical significance using the selected wavelengths. The effect of moisture was significant for both bare soil and wheat stalks, but probe height was only significant for wheat stalk samples. The index, when applied to all samples, performed well for soil samples but poorly for wheat stalk samples. Index calculations from soil reflectance measurements were highly linear (R2 > 0.95) and exhibited small variability between samples at a given moisture content, regardless of probe height. Index calculations from wheat stalk reflectance measurements were highly variable, which limited the usefulness of the index for this material. Based on these results, it is expected that crop residues, such as wheat stalks, will reduce the accuracy of remotely sensed soil surface moisture measurements.

KW - Near-infrared reflectance

KW - Normalized difference water index

KW - Remote sensing

KW - Soil moisture

KW - Spectroscopy

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JF - Transactions of the ASABE

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A method for reflectance index wavelength selection from moisture-controlled soil and crop residue samples

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

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