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Soil electrical conductivity estimated by time domain reflectometry and electromagnetic induction sensors: Accounting for the different sensor observation volumes
- Source :
- Journal of Agricultural Engineering, Vol 48, Iss 4, Pp 223-234 (2017)
- Publication Year :
- 2017
-
Abstract
- 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.
- Subjects :
- Fourierâs analysi
Soil salinity
Mechanical Engineering
lcsh:S
Inversion (meteorology)
Bioengineering
lcsh:S1-972
Industrial and Manufacturing Engineering
Electromagnetic induction
Time domain reflectometry
lcsh:Agriculture
symbols.namesake
Fourier transform
EMI
Sensors observation volume
Linear regression
Spatial ecology
symbols
Environmental science
Time domain
lcsh:Agriculture (General)
Reflectometry
Remote sensing
Fourier’s analysis
Subjects
Details
- Language :
- English
- Database :
- OpenAIRE
- Journal :
- Journal of Agricultural Engineering, Vol 48, Iss 4, Pp 223-234 (2017)
- Accession number :
- edsair.doi.dedup.....9d6ac7110a4226d9c3d9165c8edb9d80