small-scale soil moisture determination with ground
TRANSCRIPT
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Small-scale soil moisture determination withground-penetrating radar (GPR)
Jan Igel & Holger Preetz
Leibniz Institute for Applied Geophysics, Hannover, Germany
04/05/2010
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 1 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Moisture distribution in the topsoil
Depends on:
Weather conditions
Vegetation and rooting
Texture
Humus content
Bulk density
Aggregates
Cultivation
Example: Moisture distribution in asandy topsoil
In general, soil-moisture distribution is not homogeneous
The actual distribution is important for all non-linear processes(evapotranspiration, water flow, heat storage . . . )
small-scale variability is needed for numerical simulations
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 2 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Moisture distribution in the topsoil
Depends on:
Weather conditions
Vegetation and rooting
Texture
Humus content
Bulk density
Aggregates
Cultivation
Example: Moisture distribution in asandy topsoil
In general, soil-moisture distribution is not homogeneous
The actual distribution is important for all non-linear processes(evapotranspiration, water flow, heat storage . . . )
small-scale variability is needed for numerical simulations
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 2 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Moisture distribution in the topsoil
Depends on:
Weather conditions
Vegetation and rooting
Texture
Humus content
Bulk density
Aggregates
Cultivation
Example: Moisture distribution in asandy topsoil
In general, soil-moisture distribution is not homogeneous
The actual distribution is important for all non-linear processes(evapotranspiration, water flow, heat storage . . . )
small-scale variability is needed for numerical simulations
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 2 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Methods to determine soil moisture spatially
Point measurementsSoil sampling andgravimetric moisturedetermination
TDR (time-domainreflectometry)
+ simple and accurate− invasive and time consuming
Gap←→
Field and regional scale
Remote sensing
+ fast and suitable for large areas− limited spatial resolution− limited penetration in soil− influence of vegetation
There is a need for soil-moisture measurements on larger areaswith high spatial and temporal resolution→ Geophysical techniques: ERT, EMI, (MRT), GPR . . .GPR is a promising method and has been successfully used forsoil-moisture determination since several yearsChallenge: Optimise technique regarding high spatial resolutionand measuring progress
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 3 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Methods to determine soil moisture spatially
Point measurementsSoil sampling andgravimetric moisturedetermination
TDR (time-domainreflectometry)
+ simple and accurate− invasive and time consuming
Gap←→
Field and regional scale
Remote sensing
+ fast and suitable for large areas− limited spatial resolution− limited penetration in soil− influence of vegetation
There is a need for soil-moisture measurements on larger areaswith high spatial and temporal resolution→ Geophysical techniques: ERT, EMI, (MRT), GPR . . .GPR is a promising method and has been successfully used forsoil-moisture determination since several yearsChallenge: Optimise technique regarding high spatial resolutionand measuring progress
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 3 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Methods to determine soil moisture spatially
Point measurementsSoil sampling andgravimetric moisturedetermination
TDR (time-domainreflectometry)
+ simple and accurate− invasive and time consuming
Gap←→
Field and regional scale
Remote sensing
+ fast and suitable for large areas− limited spatial resolution− limited penetration in soil− influence of vegetation
There is a need for soil-moisture measurements on larger areaswith high spatial and temporal resolution→ Geophysical techniques: ERT, EMI, (MRT), GPR . . .GPR is a promising method and has been successfully used forsoil-moisture determination since several yearsChallenge: Optimise technique regarding high spatial resolutionand measuring progress
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 3 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Soil moisture determination by GPR
Dielectric permittivity is correlated to soil moisture: ε = f (ΘV )
free waterεr ≈ 80
bound waterεr « 80air
εr = 1
soil matrix4 ≤ εr ≤ 9
Groundwave
air
soil
T RT R
soil
groundwave
v ≈ c0√εsoil
r
Reflection at ground surface
air
soil
T RT R
soil
groundwave
R ≈ 1−√
εsoilr
1+√
εsoilr
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 4 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Soil moisture determination by GPR
Dielectric permittivity is correlated to soil moisture: ε = f (ΘV )
free waterεr ≈ 80
bound waterεr « 80air
εr = 1
soil matrix4 ≤ εr ≤ 9
Mixing modelsVolume dependent: Dobson, CRIM . . .Structure dependent: DeLoor, Maxwell-Garnet . . .Empirical: Topp or site specific
Groundwave
air
soil
T RT R
soil
groundwave
v ≈ c0√εsoil
r
Reflection at ground surface
air
soil
T RT R
soil
groundwave
R ≈ 1−√
εsoilr
1+√
εsoilr
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 4 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Soil moisture determination by GPR
Dielectric permittivity is correlated to soil moisture: ε = f (ΘV )
Groundwave
air
soil
T RT R
soil
groundwave
v ≈ c0√εsoil
r
Reflection at ground surface
air
soil
T RT R
soil
groundwave
R ≈ 1−√
εsoilr
1+√
εsoilr
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 4 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
GPR groundwave, principle
Moveout measurement (MO)
soil
air
T R
Simulated GPR data
slopegroundwave ∝ 1/vsoil
→ εsoil
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 5 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
GPR groundwave, principle
Moveout measurement (MO)
soil
air
T R
Simulated GPR data
slopegroundwave ∝ 1/vsoil
→ εsoil
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 5 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
GPR groundwave, principle
Moveout measurement (MO)
soil
air
T R
Simulated GPR data
slopegroundwave ∝ 1/vsoil
→ εsoil
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 5 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
GPR groundwave, principle
Moveout measurement (MO)
soil
air
T Rairwave
groundwave
Simulated GPR data
airwave
groundwave
v = dx/dt
slopegroundwave ∝ 1/vsoil
→ εsoil
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 5 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Groundwave measurements
Conventional methodfirst moveout (MO) measurementthen constant-offset (CO) measurement
82 Dielectric permittivity ε
part, x > xopt). In this mode, the permittivity distribution along a profile canbe deduced rapidly. However, it can be a challenge to identify the ground wavein solely a CO measurement especially in laterally and vertically heterogeneoussoils where numerous phases will interfere.
A combination of both methods was proposed by Du (1996) and showed to bethe most appropriate to this date. First, a moveout measurement is carried outby separating the transmitter and receiver antenna. The optimal transmitter-receiver offset xopt is determined to the distance where the air and groundwave are separated and do not influence one another or interfere with reflectedwaves. Then, the profile is mapped with a CO setup as illustrated in Fig. 4.20.This ensures the correct identification of the different phases in the radargram.
-
?
x
t
aw
gw
moveout constant offset
0 x1 xopt
∝ 1/c0
∝ 1/vsoil
Figure 4.20: Schematic traveltime diagram of a ground wave measurementconsisting of a moveout measurement from x1 to xopt followed by a constantoffset measurement at x > xopt (aw: air wave, gw: ground wave).
The approach introduced above has some basic disadvantages:
� Measurements in two modes (MO or CMP and CO) have to be carried outwhich require a modification of the layout and thus are time consuming.
� Processing and interpretation of the mixed MO and CO data is timeconsuming, too. This is especially the case when 2d permittivity distri-butions are to be determined which requires a large amount of parallelprofiles.
Drawbacks:time consuming due to two measuring modes (MO and CO)velocity determination from MO sometimes difficult (heterogeneity)lateral resolution limited by optimal T–R-distance
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 6 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Groundwave measurements
Conventional methodfirst moveout (MO) measurementthen constant-offset (CO) measurement
82 Dielectric permittivity ε
part, x > xopt). In this mode, the permittivity distribution along a profile canbe deduced rapidly. However, it can be a challenge to identify the ground wavein solely a CO measurement especially in laterally and vertically heterogeneoussoils where numerous phases will interfere.
A combination of both methods was proposed by Du (1996) and showed to bethe most appropriate to this date. First, a moveout measurement is carried outby separating the transmitter and receiver antenna. The optimal transmitter-receiver offset xopt is determined to the distance where the air and groundwave are separated and do not influence one another or interfere with reflectedwaves. Then, the profile is mapped with a CO setup as illustrated in Fig. 4.20.This ensures the correct identification of the different phases in the radargram.
-
?
x
t
aw
gw
moveout constant offset
0 x1 xopt
∝ 1/c0
∝ 1/vsoil
Figure 4.20: Schematic traveltime diagram of a ground wave measurementconsisting of a moveout measurement from x1 to xopt followed by a constantoffset measurement at x > xopt (aw: air wave, gw: ground wave).
The approach introduced above has some basic disadvantages:
� Measurements in two modes (MO or CMP and CO) have to be carried outwhich require a modification of the layout and thus are time consuming.
� Processing and interpretation of the mixed MO and CO data is timeconsuming, too. This is especially the case when 2d permittivity distri-butions are to be determined which requires a large amount of parallelprofiles.
Drawbacks:time consuming due to two measuring modes (MO and CO)velocity determination from MO sometimes difficult (heterogeneity)lateral resolution limited by optimal T–R-distance
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 6 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Groundwave measurements: Optimised layout
Layout with 2 receivers
Benefit of new layout
only time differences have to be determinedzero crossings can be picked instead of first arrivals→ easy data processing
only constant-offset measuring mode is needed→ fast measuring progress
small distance between both receivers possible→ high spatial resolution
Result of FD-simulation andexperiment
Conventional layoutlower spatial resolutionbad fit of absolute values forsmall structures
Optimised layout (2 receivers)high spatial resolutiongood fit of absolute values
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 7 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Groundwave measurements: Optimised layout
Layout with 2 receivers
Benefit of new layout
only time differences have to be determinedzero crossings can be picked instead of first arrivals→ easy data processing
only constant-offset measuring mode is needed→ fast measuring progress
small distance between both receivers possible→ high spatial resolution
Result of FD-simulation andexperiment
Conventional layoutlower spatial resolutionbad fit of absolute values forsmall structures
Optimised layout (2 receivers)high spatial resolutiongood fit of absolute values
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 7 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Groundwave measurements: Optimised layout
Layout with 2 receivers
Benefit of new layout
only time differences have to be determinedzero crossings can be picked instead of first arrivals→ easy data processing
only constant-offset measuring mode is needed→ fast measuring progress
small distance between both receivers possible→ high spatial resolution
Result of FD-simulation andexperiment
Conventional layoutlower spatial resolutionbad fit of absolute values forsmall structures
Optimised layout (2 receivers)high spatial resolutiongood fit of absolute values
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 7 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Groundwave measurements: Optimised layout
Layout with 2 receivers
Benefit of new layout
only time differences have to be determinedzero crossings can be picked instead of first arrivals→ easy data processing
only constant-offset measuring mode is needed→ fast measuring progress
small distance between both receivers possible→ high spatial resolution
Result of FD-simulation andexperiment
Conventional layoutlower spatial resolutionbad fit of absolute values forsmall structures
Optimised layout (2 receivers)high spatial resolutiongood fit of absolute values
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 7 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Groundwave measurements: Optimised layout
Layout with 2 receivers
FD-simulation (CO)
R1
R2
v = R1R2/∆t
εr = c20/v2
Result of FD-simulation andexperiment
Conventional layoutlower spatial resolutionbad fit of absolute values forsmall structures
Optimised layout (2 receivers)high spatial resolutiongood fit of absolute values
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 7 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Groundwave measurements: Optimised layout
FD-model: lateral resolution?
Background: dry sand (εr = 3)Anomalies: moist sand(εr = 9, separation = 10 cm)
FD-simulation:GPR analysis – input model
−1 −0.5 0 0.5 12
3
4
5
6
7
8
9
10
x [m]
ε r [ ]
model1 receiver
Result of FD-simulation andexperiment
Conventional layoutlower spatial resolutionbad fit of absolute values forsmall structures
Optimised layout (2 receivers)high spatial resolutiongood fit of absolute values
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 7 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Groundwave measurements: Optimised layout
FD-model: lateral resolution?
Background: dry sand (εr = 3)Anomalies: moist sand(εr = 9, separation = 10 cm)
FD-simulation:GPR analysis – input model
−1 −0.5 0 0.5 12
3
4
5
6
7
8
9
10
x [m]
ε r [ ]
model1 receiver2 receivers
Result of FD-simulation andexperiment
Conventional layoutlower spatial resolutionbad fit of absolute values forsmall structures
Optimised layout (2 receivers)high spatial resolutiongood fit of absolute values
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 7 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Groundwave measurements: Optimised layout
Sandbox setup
Background: dry sand (εr = 3)Anomaly: moist sand(εr = 5.8, width = 15 cm)
Sandbox experiment:GPR analysis – TDR data
0.25 0.5 0.75 1 1.25 1.52
3
4
5
6
7
8
x [m]
ε r [ ]
in situ1 receiver
Result of FD-simulation andexperiment
Conventional layoutlower spatial resolutionbad fit of absolute values forsmall structures
Optimised layout (2 receivers)high spatial resolutiongood fit of absolute values
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 7 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Groundwave measurements: Optimised layout
Sandbox setup
Background: dry sand (εr = 3)Anomaly: moist sand(εr = 5.8, width = 15 cm)
Sandbox experiment:GPR analysis – TDR data
0.25 0.5 0.75 1 1.25 1.52
3
4
5
6
7
8
x [m]
ε r [ ]
in situ1 receiver2 receivers
Result of FD-simulation andexperiment
Conventional layoutlower spatial resolutionbad fit of absolute values forsmall structures
Optimised layout (2 receivers)high spatial resolutiongood fit of absolute values
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 7 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Moisture by groundwave in a sandy soil (grassland)
Site 1
0 2 4 6 8 100
2
4
6
8
10
x [m]
y [m
]
ΘV [%]
0
5
10
15
anisotropy: caused by formercultivation (grassland formerlyused as tillage)
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 8 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Moisture by groundwave in a sandy soil (grassland)
Site 1
0 2 4 6 8 100
2
4
6
8
10
x [m]
y [m
]
ΘV [%]
0
5
10
15
anisotropy: caused by formercultivation (grassland formerlyused as tillage)
Density function
0 5 10 15 200
0.1
0.2
0.3
ΘV [%]
p
datafit
normal distr.ΘV = 9±2%
Variograms94 Dielectric permittivity ε
0 1 2 3 40
0.2
0.4
0.6
0.8
1
h [m]
γ [ ]
x−direction
0 1 2 3 40
0.2
0.4
0.6
0.8
1
h [m]
γ [ ]
y−direction
Figure 4.30: Statistical analysis of the permittivity distribution determinedwith the ground wave at location 2. The directional variogram is calculated inx- and y-direction and an exponential model is fitted to the curves. The rangeof the fitted models is: ax = 1.0 m and ay = 0.3 m.
also be observed in this data might be explained as the trace of a vehicle.
amax = 1.5 m, amin = 0.3 m
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 8 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Moisture by groundwave in a sandy soil (grassland)
Site 1
0 2 4 6 8 100
2
4
6
8
10
x [m]
y [m
]
ΘV [%]
0
5
10
15
anisotropy: caused by formercultivation (grassland formerlyused as tillage)
Site 2
0 2 4 6 8 100
2
4
6
8
10
x [m]
y [m
]
ΘV [%]
0
5
10
15
isotropic pattern: area formerlynot used as tillage⇒ natural variability, a = 0.35 m
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 8 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Reflection at soil surface
Measuring layout Reflection at metal, soil and soilcovered by grass
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 9 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Reflection at soil surface
Measuring layout Reflection at metal, soil and soilcovered by grass
4.3 Determining the permittivity by the coefficient of reflection 69
metal soil soil + vegetation0
2
4
6
8
10
12
14
16
t [ns
]
normalised amplitude [ ]
Figure 4.8: Radar trace of a 1 GHz horn antenna showing a wave reflectedat a metal plate, a soil surface without vegetation and a soil surface withvegetation. The amplitude is normalised to the maximum amplitude of themetal reflection.
resolution.
Therefore, the footprint6 of the used horn antenna is determined by an exper-iment. The antenna is operated into the air and an aluminium foil is placed atthe same distance to the antenna as the ground will be during the field mea-surements. The size of the foil is varied stepwise and a radar trace is recordedin each case. In Fig. 4.9 the amplitude of the reflected wave is plotted versusthe size of the metal reflector. The size is varied in the direction perpendicularto the E-field of the emitted waves (i.e. the common profile direction of the an-tenna, see Fig. 4.7) while it is hold constant and is larger than the first Fresnelzone in the other direction (i.e. perpendicular to the normal profile direction).Then, the same experiment is carried out in the other direction, i.e. the sizeof the metal reflector is varied parallel to the E-field. The amplitudes are nor-malised to the reflection of a large metal plate. The amplitude of the reflected
6The footprint is the area which is illuminated by an antenna and defines the lateralresolution (Wessel, 2006).
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 9 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Field measurement
Reflection, site 1
0 2 4 6 8 100
2
4
6
8
10
x [m]
y [m
]
ΘV [%]
0
5
10
15
Groundwave, site 1
same pattern caused by cultivationsmall differences of absolute values and variability due to differentsampling depth and lateral resolution (≈ 25 cm vs. 13 cm)
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 10 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Field measurement
Reflection, site 1
0 2 4 6 8 100
2
4
6
8
10
x [m]
y [m
]
ΘV [%]
0
5
10
15
Groundwave, site 1
0 2 4 6 8 100
2
4
6
8
10
x [m]
y [m
]
ΘV [%]
0
5
10
15
same pattern caused by cultivationsmall differences of absolute values and variability due to differentsampling depth and lateral resolution (≈ 25 cm vs. 13 cm)
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 10 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Conclusion
GPR groundwave technique has been optimised regarding lateralresolution (≈ 10 cm) and measuring progress.
Analysing reflections at the ground surface shows similar results.
GPR can be used for fast, non-invasive, high-resolutionsoil-moisture mapping and provide important input for realisticnumerical simulations.Field measuremets on different grassland-sites demonstrate that
soil moisture shows high variability with correlation length of a fewdecimetressoil moisture distribution is influenced by the former cultivation andsoil may preserve this effect for a longer time.
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 11 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Conclusion
GPR groundwave technique has been optimised regarding lateralresolution (≈ 10 cm) and measuring progress.
Analysing reflections at the ground surface shows similar results.
GPR can be used for fast, non-invasive, high-resolutionsoil-moisture mapping and provide important input for realisticnumerical simulations.Field measuremets on different grassland-sites demonstrate that
soil moisture shows high variability with correlation length of a fewdecimetressoil moisture distribution is influenced by the former cultivation andsoil may preserve this effect for a longer time.
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 11 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Open questions and outlook
Vegetation has an impact on measuring results.Depth of investigation of the groundwave is still an object ofresearchz = fct (frequency, antenna separation, ε-distribution)→ inversion might provide information on the moisturedistribution with depth and further enhance lateral resolution.
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 12 /12
Title Motivation GPR–Moisture GPR–Groundwave GPR–Reflection Conclusion
Open questions and outlook
Vegetation has an impact on measuring results.Depth of investigation of the groundwave is still an object ofresearchz = fct (frequency, antenna separation, ε-distribution)→ inversion might provide information on the moisturedistribution with depth and further enhance lateral resolution.
EGU 2010 J. Igel & H. Preetz, LIAG Hannover Small-scale soil moisture determination with GPR 12 /12