Mitigation of Tropospheric Delay in SAR and InSAR Using NWP Data: Its Validation and Application Examples
Abstract
:1. Introduction
2. Methodology
2.1. Atmospheric Path Delay in the Neutral Atmosphere
2.1.1. Air Refractivity and Neutral Atmospheric Propagation Delay
2.1.2. Integration of the Neutral Atmospheric Delay and Its Alternative Expressions
- (1)
- ;
- (2)
- ;
- (3)
- .
2.1.3. Coefficient Constants
2.2. Direct Integration Method Using Global NWP Products
2.3. Terminology: Tropospheric Delay
3. Validation of Integrated Tropospheric Delay
3.1. ECMWF Products
3.2. Validation Approaches
3.3. Validation of Integrated ZPD with GPS ZPD
3.3.1. Time-Series Comparison Using ERA-Interim and OP Data Sets at the Wettzell Station
3.3.2. Global Validation of ERA-Interim Products
3.4. Validation of Integrated SPD with SPD Estimated from CR Measurements
4. Applications
4.1. Application to Absolute Ranging Measurements
4.2. Application to Interferometric Measurements
4.2.1. PSI Processing—Test Site: Stromboli Volcano, Italy
4.2.2. Wide Area Interferometry—Sentinel-1 Interferogram
5. Conclusions
Author Contributions
Acknowledgments
Conflicts of Interest
Abbreviations
APL | Atmospheric pressure loading |
ASC | Ascending |
CD | Continental drift |
CR | Corner reflector |
DEM | Digital elevation model |
DLR | German Aerospace Center |
DSC | Descending |
ECMWF | European Centre for Medium-Range Weather Forecasts |
GNSS | Global navigation satellite system |
GPS | Global positioning system |
HRSL | High Resolution SpotLight |
ID | Ionospheric delay |
IFS | Integrated forecast system |
IGS | International GNSS Service |
InSAR | SAR interferometry |
METS | CR test site in Metaähovi (Finland) |
ML | Model level |
NWP | Numerical weather prediction |
OHIS | CR test site in GARS O’Higgins at the Antarctic Peninsula |
OMT | Overall model test |
OP | Operational data |
OTL | Ocean tidal loading. |
PSI | Persistent Scatterer (PS) interferometry |
SAR | Synthetic aperture radar |
SCR | Signal-to-Clutter Ratio |
SET | Solid Earth tide |
SPD | Slant range path delay |
SWD | Slant range wet delay |
TEC | Total electron content. |
TDX-1 | German TanDEM-X satellite |
TSX-1 | German TerraSAR-X satellite |
WTZR | Wettzell GNSS station in EPN (Germany) |
ZHD | Zenith hydrostatic delay |
ZPD | Zenith path delay |
ZWD | Zenith wet delay |
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Authors (Year) | (K/hPa) | (K/hPa) | (K/ hPa) | ZPD Diff. (mm) | |
---|---|---|---|---|---|
Mean | Std | ||||
Ideal Gas | |||||
Smith and Weintraubt [18] | |||||
Saastamoinen [21] | |||||
Rüeger [25] (best available) | <0.1 | ||||
Rüeger [25] (best average) | <0.1 | ||||
Healy [19] | <0.1 | ||||
Non-ideal Gases | |||||
Thayer [22] | |||||
Davis et al. [23] | |||||
Healy [19] | |||||
Non-ideal Gases—Approximated Equation | |||||
Bevis et al. [24] |
ECMWF Products | Horizontal Resolution (deg) | Vertical Resolution | IFS Release | Release Date |
---|---|---|---|---|
Operational | 0.100 | 137-Level | Cycle 41r2 | 8 March 2016 |
0.125 | 137-Level | Cycle 38r2 | 26 June 2013 | |
0.125 | 91-Level | Cycle 38r1 | 11 March 2008 | |
0.225 | 91-Level | Cycle 30r1 | 1 February 2006 | |
0.350 | 60-Level | Cycle 23r3 | 21 November 2000 | |
ERA-Interim | 0.750 | 60-Level | Cycle 31r2 | 1 January 2006 |
ERA5 | 0.280 | 137-Level | Cycle 41r2 | 1 January 2018 |
CR ID | Input Data | Mean (mm) | STD (mm) |
---|---|---|---|
WTZR 01 (ASC) | GPS ZPD | ||
ERA-Interim | |||
Operational | |||
WTZR 02 (DSC) | GPS ZPD | ||
ERA-Interim | |||
Operational | |||
METS (DSC) | GPS ZPD | ||
ERA-Interim | |||
Operational |
Test Site Code | Crossing Orbit Direction | IGS SPD | ECMWF SPD | ||
---|---|---|---|---|---|
Mean (mm) | STD (mm) | Mean (mm) | STD [mm] | ||
WTZR | ASC | ||||
DSC | |||||
OHIS | ASC | ||||
DSC | |||||
METS | DSC |
Beam | (mm/year) | (m) | ||||
---|---|---|---|---|---|---|
Nr. | Max | Min | Corr. (-) | Max | Min | Corr. (-) |
033 | ||||||
061 | ||||||
069 | ||||||
024 |
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Cong, X.; Balss, U.; Rodriguez Gonzalez, F.; Eineder, M. Mitigation of Tropospheric Delay in SAR and InSAR Using NWP Data: Its Validation and Application Examples. Remote Sens. 2018, 10, 1515. https://doi.org/10.3390/rs10101515
Cong X, Balss U, Rodriguez Gonzalez F, Eineder M. Mitigation of Tropospheric Delay in SAR and InSAR Using NWP Data: Its Validation and Application Examples. Remote Sensing. 2018; 10(10):1515. https://doi.org/10.3390/rs10101515
Chicago/Turabian StyleCong, Xiaoying, Ulrich Balss, Fernando Rodriguez Gonzalez, and Michael Eineder. 2018. "Mitigation of Tropospheric Delay in SAR and InSAR Using NWP Data: Its Validation and Application Examples" Remote Sensing 10, no. 10: 1515. https://doi.org/10.3390/rs10101515