Error in Radar-Derived Soil Moisture due to Roughness Parameterization: An Analysis Based on Synthetical Surface Profiles
<p>Backscatter coefficients calculated for different values of RMS height and correlation length and a moisture content of 25 vol% for (a) an ASAR VV configuration and (b) a PALSAR HH configuration.</p> ">
<p>Backscatter coefficients calculated for different values of RMS height and correlation length and a moisture content of 25 vol% for (a) an ASAR VV configuration and (b) a PALSAR HH configuration.</p> ">
<p>Sensitivity of the soil moisture retrieval to RMS height (vol%/cm) for an ASAR VV configuration and a moisture content of (a) 5 vol%, (b) 15 vol%, (c) 25 vol%, and (d) 35 vol%.</p> ">
<p>Sensitivity of the soil moisture retrieval to RMS height (vol%/cm) for an ASAR VV configuration and a moisture content of (a) 5 vol%, (b) 15 vol%, (c) 25 vol%, and (d) 35 vol%.</p> ">
<p>Sensitivity of the soil moisture retrieval to RMS height (vol%/cm) for an ASAR VV configuration and a moisture content of (a) 5 vol%, (b) 15 vol%, (c) 25 vol%, and (d) 35 vol%.</p> ">
<p>Sensitivity of the soil moisture retrieval to RMS height (vol%/cm) for an ASAR VV configuration and a moisture content of (a) 5 vol%, (b) 15 vol%, (c) 25 vol%, and (d) 35 vol%.</p> ">
<p>Sensitivity of the soil moisture retrieval to correlation length (vol%/cm) for an ASAR VV configuration and a moisture content of (a) 5vol%, (b) 15vol%, (c) 25vol%, and (d) 35vol%.</p> ">
<p>Sensitivity of the soil moisture retrieval to correlation length (vol%/cm) for an ASAR VV configuration and a moisture content of (a) 5vol%, (b) 15vol%, (c) 25vol%, and (d) 35vol%.</p> ">
<p>Sensitivity of the soil moisture retrieval to correlation length (vol%/cm) for an ASAR VV configuration and a moisture content of (a) 5vol%, (b) 15vol%, (c) 25vol%, and (d) 35vol%.</p> ">
<p>Sensitivity of the soil moisture retrieval to correlation length (vol%/cm) for an ASAR VV configuration and a moisture content of (a) 5vol%, (b) 15vol%, (c) 25vol%, and (d) 35vol%.</p> ">
<p>Sensitivity of the soil moisture retrieval to RMS height (vol%/cm) for a PALSAR HH configuration and a moisture content of (a) 5 vol%, (b) 15 vol%, (c) 25 vol%, and (d) 35 vol%.</p> ">
<p>Sensitivity of the soil moisture retrieval to RMS height (vol%/cm) for a PALSAR HH configuration and a moisture content of (a) 5 vol%, (b) 15 vol%, (c) 25 vol%, and (d) 35 vol%.</p> ">
<p>Sensitivity of the soil moisture retrieval to RMS height (vol%/cm) for a PALSAR HH configuration and a moisture content of (a) 5 vol%, (b) 15 vol%, (c) 25 vol%, and (d) 35 vol%.</p> ">
<p>Sensitivity of the soil moisture retrieval to RMS height (vol%/cm) for a PALSAR HH configuration and a moisture content of (a) 5 vol%, (b) 15 vol%, (c) 25 vol%, and (d) 35 vol%.</p> ">
<p>Sensitivity of the soil moisture retrieval to correlation length (vol%/cm) for a PALSAR HH configuration and a moisture content of (a) 5vol%, (b) 15vol%, (c) 25 vol%, and (d) 35 vol%.</p> ">
<p>Sensitivity of the soil moisture retrieval to correlation length (vol%/cm) for a PALSAR HH configuration and a moisture content of (a) 5vol%, (b) 15vol%, (c) 25 vol%, and (d) 35 vol%.</p> ">
<p>Sensitivity of the soil moisture retrieval to correlation length (vol%/cm) for a PALSAR HH configuration and a moisture content of (a) 5vol%, (b) 15vol%, (c) 25 vol%, and (d) 35 vol%.</p> ">
<p>Sensitivity of the soil moisture retrieval to correlation length (vol%/cm) for a PALSAR HH configuration and a moisture content of (a) 5vol%, (b) 15vol%, (c) 25 vol%, and (d) 35 vol%.</p> ">
<p>Mean and standard deviations of RMS height and correlation length for different profile lengths, sampled from large profiles with (a) (<span class="html-italic">s,l</span>) = (1 cm,5 cm) and (b) (<span class="html-italic">s,l</span>) = (1 cm,40 cm).</p> ">
<p>Mean and standard deviations of RMS height and correlation length for different profile lengths, sampled from large profiles with (a) (<span class="html-italic">s,l</span>) = (1 cm,5 cm) and (b) (<span class="html-italic">s,l</span>) = (1 cm,40 cm).</p> ">
<p>Mean and standard deviations of inverted soil moisture contents for different profile lengths. Inverted soil moisture contents are derived using roughness parameters from sampled profiles, originating from large profiles with (<span class="html-italic">s,l</span>) equal to (a), (b) (2 cm,5 cm), (c), (d) (1 cm,5 cm), (e), (f) (2 cm,40 cm) and (g), (h) (1 cm,40 cm), and initial moisture contents of (a), (c), (e), (g) 5 vol% and (b), (d), (f), (h) 25 vol%.</p> ">
<p>Mean and standard deviations of inverted soil moisture contents for different profile lengths. Inverted soil moisture contents are derived using roughness parameters from sampled profiles, originating from large profiles with (<span class="html-italic">s,l</span>) equal to (a), (b) (2 cm,5 cm), (c), (d) (1 cm,5 cm), (e), (f) (2 cm,40 cm) and (g), (h) (1 cm,40 cm), and initial moisture contents of (a), (c), (e), (g) 5 vol% and (b), (d), (f), (h) 25 vol%.</p> ">
<p>Mean and standard deviations of inverted soil moisture contents for different profile lengths. Inverted soil moisture contents are derived using roughness parameters from sampled profiles, originating from large profiles with (<span class="html-italic">s,l</span>) equal to (a), (b) (2 cm,5 cm), (c), (d) (1 cm,5 cm), (e), (f) (2 cm,40 cm) and (g), (h) (1 cm,40 cm), and initial moisture contents of (a), (c), (e), (g) 5 vol% and (b), (d), (f), (h) 25 vol%.</p> ">
<p>Mean and standard deviations of inverted soil moisture contents for different profile lengths. Inverted soil moisture contents are derived using roughness parameters from sampled profiles, originating from large profiles with (<span class="html-italic">s,l</span>) equal to (a), (b) (2 cm,5 cm), (c), (d) (1 cm,5 cm), (e), (f) (2 cm,40 cm) and (g), (h) (1 cm,40 cm), and initial moisture contents of (a), (c), (e), (g) 5 vol% and (b), (d), (f), (h) 25 vol%.</p> ">
<p>Mean and standard deviations of inverted soil moisture contents for different profile lengths. Inverted soil moisture contents are derived using roughness parameters from sampled profiles, originating from large profiles with (<span class="html-italic">s,l</span>) equal to (a), (b) (2 cm,5 cm), (c), (d) (1 cm,5 cm), (e), (f) (2 cm,40 cm) and (g), (h) (1 cm,40 cm), and initial moisture contents of (a), (c), (e), (g) 5 vol% and (b), (d), (f), (h) 25 vol%.</p> ">
<p>Mean and standard deviations of inverted soil moisture contents for different profile lengths. Inverted soil moisture contents are derived using roughness parameters from sampled profiles, originating from large profiles with (<span class="html-italic">s,l</span>) equal to (a), (b) (2 cm,5 cm), (c), (d) (1 cm,5 cm), (e), (f) (2 cm,40 cm) and (g), (h) (1 cm,40 cm), and initial moisture contents of (a), (c), (e), (g) 5 vol% and (b), (d), (f), (h) 25 vol%.</p> ">
<p>Mean and standard deviations of inverted soil moisture contents for different profile lengths. Inverted soil moisture contents are derived using roughness parameters from sampled profiles, originating from large profiles with (<span class="html-italic">s,l</span>) equal to (a), (b) (2 cm,5 cm), (c), (d) (1 cm,5 cm), (e), (f) (2 cm,40 cm) and (g), (h) (1 cm,40 cm), and initial moisture contents of (a), (c), (e), (g) 5 vol% and (b), (d), (f), (h) 25 vol%.</p> ">
<p>Mean and standard deviations of inverted soil moisture contents for different profile lengths. Inverted soil moisture contents are derived using roughness parameters from sampled profiles, originating from large profiles with (<span class="html-italic">s,l</span>) equal to (a), (b) (2 cm,5 cm), (c), (d) (1 cm,5 cm), (e), (f) (2 cm,40 cm) and (g), (h) (1 cm,40 cm), and initial moisture contents of (a), (c), (e), (g) 5 vol% and (b), (d), (f), (h) 25 vol%.</p> ">
<p>Number of profiles required to obtain a standard deviation of RMS height or correlation length less than 10% of the mean for different profile lengths. Sampled profiles originate from large profiles with (<span class="html-italic">s,l</span>) equal to (a) (1 cm,5 cm) and (b) (1 cm,40 cm).</p> ">
<p>Number of profiles required to obtain a standard deviation of RMS height or correlation length less than 10% of the mean for different profile lengths. Sampled profiles originate from large profiles with (<span class="html-italic">s,l</span>) equal to (a) (1 cm,5 cm) and (b) (1 cm,40 cm).</p> ">
<p>Mean and standard deviations of inverted soil moisture contents for different numbers of profiles used. Inverted soil moisture contents are derived using roughness parameter series from sampled 4-m profiles, originating from large profiles with (<span class="html-italic">s,l</span>) equal to (a), (b) (1 cm,5 cm) and (c), (d) (1cm,40 cm), and for (a), (c) ASAR VV and (b), (d) PALSAR HH. Considered initial moisture contents are 5 vol% (crosses), 15 vol% (circles), 25 vol% (stars) and 35 vol% (squares).</p> ">
<p>Mean and standard deviations of inverted soil moisture contents for different numbers of profiles used. Inverted soil moisture contents are derived using roughness parameter series from sampled 4-m profiles, originating from large profiles with (<span class="html-italic">s,l</span>) equal to (a), (b) (1 cm,5 cm) and (c), (d) (1cm,40 cm), and for (a), (c) ASAR VV and (b), (d) PALSAR HH. Considered initial moisture contents are 5 vol% (crosses), 15 vol% (circles), 25 vol% (stars) and 35 vol% (squares).</p> ">
<p>Mean and standard deviations of inverted soil moisture contents for different numbers of profiles used. Inverted soil moisture contents are derived using roughness parameter series from sampled 4-m profiles, originating from large profiles with (<span class="html-italic">s,l</span>) equal to (a), (b) (1 cm,5 cm) and (c), (d) (1cm,40 cm), and for (a), (c) ASAR VV and (b), (d) PALSAR HH. Considered initial moisture contents are 5 vol% (crosses), 15 vol% (circles), 25 vol% (stars) and 35 vol% (squares).</p> ">
<p>Mean and standard deviations of inverted soil moisture contents for different numbers of profiles used. Inverted soil moisture contents are derived using roughness parameter series from sampled 4-m profiles, originating from large profiles with (<span class="html-italic">s,l</span>) equal to (a), (b) (1 cm,5 cm) and (c), (d) (1cm,40 cm), and for (a), (c) ASAR VV and (b), (d) PALSAR HH. Considered initial moisture contents are 5 vol% (crosses), 15 vol% (circles), 25 vol% (stars) and 35 vol% (squares).</p> ">
Abstract
:1. Introduction
- A series of surface height points (roughness profile) is defined along a 1-dimensional surface transect, mostly sampled by means of meshboard, pin profilometer or laser techniques [6]. Generally, profiles used in practice have a length between 1 m and 4 m [6–9], and the horizontal spacing between height points usually lies between 1 mm [5] and 2 cm [7].
- From this profile a linear trend is removed to compensate for the possibility that the measurement device was not aligned perfectly parallel to a horizontal reference surface [8].
2. Soil moisture retrieval technique
3. Sensitivity of soil moisture retrieval to RMS height and correlation length
4. Sensitivity of soil moisture retrieval to roughness parameterization techniques
4.1. Generation of synthetical 1-dimensional surface profiles
4.2. Profile length
Experimental setup
Errors on roughness parameterization
Errors on soil moisture retrieval
4.3. Number of profile measurements
Experimental setup
Errors on roughness parameterization
Errors on soil moisture retrieval
4.4. Spacing between height points
Experimental setup
Errors on roughness parameterization
Errors on soil moisture retrieval
4.5. Instrument accuracy
Experimental setup
Errors on roughness parameterization
Errors on soil moisture retrieval
4.6. Trend removal
Experimental setup
Errors on roughness parameterization
Errors on soil moisture retrieval
5. Conclusions
Acknowledgments
References and Notes
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Model | Parameter | Value |
---|---|---|
Integral Equation Model | ||
ENVISAT ASAR configuration | Frequency | 5.3 GHz (C-band) |
Polarization | HH or VV | |
Incidence angle | 23° | |
ALOS PALSAR configuration | Frequency | 1.27 GHz (L-band) |
Polarization | HH or VV | |
Incidence angle | 34.3° | |
4-Component Dielectric Mixing Model | Bulk density | 1.2 g/cm3 |
Specific density | 2.65 g/cm3 | |
Sand content | 15% | |
Clay content | 11.4% | |
Temperature | 15°C |
Sample spacing | |||||
---|---|---|---|---|---|
‘Truth’ (1 mm) | 2mm | 5mm | 10mm | 15mm | |
s (cm) | 1 | 0.99 (0.00) | 0.98 (0.00) | 0.97 (0.01) | 0.96 (0.02) |
l (cm) | 5 | 5.02 (0.04) | 5.15 (0.11) | 5.34 (0.22) | 5.47 (0.40) |
s (cm) | 1 | 1.00 (0.00) | 1.00 (0.00) | 1.00 (0.00) | 0.99 (0.00) |
l (cm) | 40 | 40.02 (0.04) | 40.07 (0.21) | 40.20 (0.41) | 40.23 (0.37) |
s (cm) | 2 | 1.99 (0.01) | 1.97 (0.01) | 1.93 (0.02) | 1.91 (0.01) |
l (cm) | 5 | 5.07 (0.05) | 5.17 (0.08) | 5.43 (0.19) | 5.76 (0.52) |
s (cm) | 2 | 2.00 (0.00) | 2.00 (0.00) | 2.00 (0.01) | 1.99 (0.01) |
l (cm) | 40 | 40.03 (0.05) | 40.16 (0.28) | 40.30 (0.45) | 40.26 (0.58) |
Correct (s,l) | RMSE on s or l due to | |||||
---|---|---|---|---|---|---|
1mm noise | 2mm noise | 5mm noise | ||||
s (cm) | l (cm) | s (cm) | l (cm) | s (cm) | l (cm) | |
(1 cm,5 cm) | 0.0019 | 0.0316 | 0.0074 | 0.0775 | 0.0443 | 0.3782 |
(1 cm,40 cm) | 0.0017 | 0.1673 | 0.0068 | 0.4764 | 0.0421 | 2.9972 |
(2 cm,5 cm) | 0.0015 | 0.0447 | 0.0043 | 0.0316 | 0.0215 | 0.1265 |
(2 cm,40 cm) | 0.0009 | 0.0707 | 0.0035 | 0.1871 | 0.0219 | 0.9301 |
(s,l) of original profile | Soil moisture content (vol%) | RMSE (vol%) of retrieved soil moisture due to | |||
---|---|---|---|---|---|
1 mm noise | 2 mm noise | 5 mm noise | |||
(1 cm,5 cm) | 5 | 0.04 | 0.11 | 0.54 | |
(1 cm,5 cm) | 15 | 0.11 | 0.30 | 1.39 | |
(1 cm,5 cm) | 25 | 0.21 | 0.57 | 2.61 | |
(1 cm,5 cm) | 35 | 0.34 | 0.92 | 4.15 | |
(1 cm,40 cm) | 35 | 0.39 | 2.08 | 8.31 | |
(2 cm,5 cm) | 35 | 0.24 | 0.26 | 0.51 | |
(2 cm,40 cm) | 35 | 0.23 | 0.46 | 2.76 |
Correct roughness values | ||||||||
---|---|---|---|---|---|---|---|---|
s (cm) | l (cm) | s (cm) | l (cm) | s (cm) | l (cm) | s (cm) | l (cm) | |
1 | 5 | 1 | 40 | 2 | 5 | 2 | 40 | |
Detrending type | Linear trended surface | |||||||
Linear 4-m | 0.99 (0.01) | 4.93 (0.13) | 0.91 (0.07) | 30.09 (7.48) | 1.97 (0.03) | 4.76 (0.25) | 1.80 (0.18) | 31.57 (6.00) |
Piecewise 1-m | 0.92 (0.03) | 3.80 (0.45) | 0.51 (0.04) | 8.31 (1.34) | 1.85 (0.06) | 3.77 (0.40) | 0.98 (0.12) | 7.45 (1.12) |
Second-order | 0.98 (0.02) | 4.67 (0.29) | 0.81 (0.10) | 24.22 (7.40) | 1.94 (0.04) | 4.51 (0.26) | 1.57 (0.19) | 22.00 (7.58) |
Third-order | 0.96 (0.02) | 4.36 (0.30) | 0.64 (0.05) | 15.02 (3.96) | 1.93 (0.03) | 4.37 (0.26) | 1.41 (0.16) | 17.84 (6.18) |
Cosine trended surface | ||||||||
Linear 4-m | 2.64 (0.13) | 50.07 (2.25) | 2.78 (0.42) | 54.30 (4.68) | 3.07 (0.26) | 28.13 (8.31) | 3.01 (0.74) | 44.81 (7.06) |
Piecewise 1-m | 0.95 (0.04) | 4.13 (0.49) | 0.58 (0.06) | 9.40 (1.47) | 1.85 (0.05) | 3.79 (0.36) | 1.00 (0.10) | 7.79 (1.47) |
Second-order | 1.32 (0.13) | 13.48 (6.67) | 1.10 (0.35) | 25.47 (8.16) | 2.17 (0.13) | 7.19 (2.03) | 1.88 (0.27) | 28.38 (8.27) |
Third-order | 1.04 (0.04) | 5.33 (0.53) | 0.79 (0.12) | 18.16 (4.72) | 1.95 (0.05) | 4.53 (0.30) | 1.47 (0.12) | 18.81 (5.13) |
© 2009 by the authors; licensee Molecular Diversity Preservation International, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).
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Lievens, H.; Vernieuwe, H.; Álvarez-Mozos, J.; De Baets, B.; Verhoest, N.E.C. Error in Radar-Derived Soil Moisture due to Roughness Parameterization: An Analysis Based on Synthetical Surface Profiles. Sensors 2009, 9, 1067-1093. https://doi.org/10.3390/s90201067
Lievens H, Vernieuwe H, Álvarez-Mozos J, De Baets B, Verhoest NEC. Error in Radar-Derived Soil Moisture due to Roughness Parameterization: An Analysis Based on Synthetical Surface Profiles. Sensors. 2009; 9(2):1067-1093. https://doi.org/10.3390/s90201067
Chicago/Turabian StyleLievens, Hans, Hilde Vernieuwe, Jesús Álvarez-Mozos, Bernard De Baets, and Niko E.C. Verhoest. 2009. "Error in Radar-Derived Soil Moisture due to Roughness Parameterization: An Analysis Based on Synthetical Surface Profiles" Sensors 9, no. 2: 1067-1093. https://doi.org/10.3390/s90201067
APA StyleLievens, H., Vernieuwe, H., Álvarez-Mozos, J., De Baets, B., & Verhoest, N. E. C. (2009). Error in Radar-Derived Soil Moisture due to Roughness Parameterization: An Analysis Based on Synthetical Surface Profiles. Sensors, 9(2), 1067-1093. https://doi.org/10.3390/s90201067