Soil electrical conductivity estimated by time domain reflectometry and electromagnetic induction sensors: Accounting for the different sensor observation volumes

This paper dealt with the calibration of an EMI sensor for monitoring the time dynamics of root zone salinity under irrigation with saline water. Calibration was based on an empirical multiple regression approach largely adopted in the past and still applied in practice for its relative simplicity....

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Main Authors: Ali Saeed, Alessandro Comegna, Giovanna Dragonetti, Nicola Lamaddalena, Angelo Sommella, Antonio Coppola
Format: Article
Language:English
Published: PAGEPress Publications 2017-12-01
Series:Journal of Agricultural Engineering
Subjects:
Online Access:http://www.agroengineering.org/index.php/jae/article/view/716
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spelling doaj-3db1ccd0bf4f403587c7f10bb96540632020-11-25T03:35:49ZengPAGEPress PublicationsJournal of Agricultural Engineering1974-70712239-62682017-12-0148422323410.4081/jae.2017.716480Soil electrical conductivity estimated by time domain reflectometry and electromagnetic induction sensors: Accounting for the different sensor observation volumesAli Saeed0Alessandro Comegna1Giovanna Dragonetti2Nicola Lamaddalena3Angelo Sommella4Antonio Coppola5School of Agricultural, Forestry, Food and Environmental Sciences, University of Basilicata, PotenzaSchool of Agricultural, Forestry, Food and Environmental Sciences, University of Basilicata, PotenzaLand and Water Division, Mediterranean Agronomic Institute - International Centre for Advanced Mediterranean Agronomic Studies, BariLand and Water Division, Mediterranean Agronomic Institute - International Centre for Advanced Mediterranean Agronomic Studies, BariDepartment of Agriculture, Federico II University, NaplesSchool of Agricultural, Forestry, Food and Environmental Sciences, University of Basilicata, PotenzaThis paper dealt with the calibration of an EMI sensor for monitoring the time dynamics of root zone salinity under irrigation with saline water. Calibration was based on an empirical multiple regression approach largely adopted in the past and still applied in practice for its relative simplicity. Compared to the more complex inversion approaches, it requires an independent dataset of local σb measured within discrete depth intervals, to be compared to horizontal and vertical electrical conductivity (ECaH and ECaV) readings for estimating the parameters of the empirical regression equations. In this paper, we used time domain reflectometry (TDR) readings to replace direct sampling for these local σb measurements. When using this approach, there is the important issue of taking into account the effect of the different sensor observation volumes, making the readings not immediately comparable for empirical calibration. Accordingly, a classical Fourier’s filtering technique was applied to remove the high frequency part (at small spatial scale) of the original data variability, which, due to the different observation volume, was the main source of dissimilarity between the two datasets. Thus, calibration focused only on the lower frequency information, that is, the information at a spatial scale larger than the observation volume of the sensors. By this analysis, we showed and quantified the degree to which the information of the set of TDR readings came from a combination of local and larger scale heterogeneities and how they have to be manipulated for use in EMI electromagnetic induction sensor calibration.http://www.agroengineering.org/index.php/jae/article/view/716Soil salinityelectromagnetic inductiontime domain reflectometrysensors observation volumeFourier’s analysis.
collection DOAJ
language English
format Article
sources DOAJ
author Ali Saeed
Alessandro Comegna
Giovanna Dragonetti
Nicola Lamaddalena
Angelo Sommella
Antonio Coppola
spellingShingle Ali Saeed
Alessandro Comegna
Giovanna Dragonetti
Nicola Lamaddalena
Angelo Sommella
Antonio Coppola
Soil electrical conductivity estimated by time domain reflectometry and electromagnetic induction sensors: Accounting for the different sensor observation volumes
Journal of Agricultural Engineering
Soil salinity
electromagnetic induction
time domain reflectometry
sensors observation volume
Fourier’s analysis.
author_facet Ali Saeed
Alessandro Comegna
Giovanna Dragonetti
Nicola Lamaddalena
Angelo Sommella
Antonio Coppola
author_sort Ali Saeed
title Soil electrical conductivity estimated by time domain reflectometry and electromagnetic induction sensors: Accounting for the different sensor observation volumes
title_short Soil electrical conductivity estimated by time domain reflectometry and electromagnetic induction sensors: Accounting for the different sensor observation volumes
title_full Soil electrical conductivity estimated by time domain reflectometry and electromagnetic induction sensors: Accounting for the different sensor observation volumes
title_fullStr Soil electrical conductivity estimated by time domain reflectometry and electromagnetic induction sensors: Accounting for the different sensor observation volumes
title_full_unstemmed Soil electrical conductivity estimated by time domain reflectometry and electromagnetic induction sensors: Accounting for the different sensor observation volumes
title_sort soil electrical conductivity estimated by time domain reflectometry and electromagnetic induction sensors: accounting for the different sensor observation volumes
publisher PAGEPress Publications
series Journal of Agricultural Engineering
issn 1974-7071
2239-6268
publishDate 2017-12-01
description This paper dealt with the calibration of an EMI sensor for monitoring the time dynamics of root zone salinity under irrigation with saline water. Calibration was based on an empirical multiple regression approach largely adopted in the past and still applied in practice for its relative simplicity. Compared to the more complex inversion approaches, it requires an independent dataset of local σb measured within discrete depth intervals, to be compared to horizontal and vertical electrical conductivity (ECaH and ECaV) readings for estimating the parameters of the empirical regression equations. In this paper, we used time domain reflectometry (TDR) readings to replace direct sampling for these local σb measurements. When using this approach, there is the important issue of taking into account the effect of the different sensor observation volumes, making the readings not immediately comparable for empirical calibration. Accordingly, a classical Fourier’s filtering technique was applied to remove the high frequency part (at small spatial scale) of the original data variability, which, due to the different observation volume, was the main source of dissimilarity between the two datasets. Thus, calibration focused only on the lower frequency information, that is, the information at a spatial scale larger than the observation volume of the sensors. By this analysis, we showed and quantified the degree to which the information of the set of TDR readings came from a combination of local and larger scale heterogeneities and how they have to be manipulated for use in EMI electromagnetic induction sensor calibration.
topic Soil salinity
electromagnetic induction
time domain reflectometry
sensors observation volume
Fourier’s analysis.
url http://www.agroengineering.org/index.php/jae/article/view/716
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