scholarly journals Application of a high-resolution weather model in the area of the western Gulf of Corinth for the troposhperic correction of interferometric synthetic aperture radar (InSAR) observations

2019 ◽  
Author(s):  
Νικόλαος Ρουκουνάκης
Keyword(s):  
Water Vapor ◽  
High Resolution ◽  
Synthetic Aperture Radar ◽  
Precise Point Positioning ◽  
Synthetic Aperture ◽  
Interferometric Synthetic Aperture Radar ◽  
Gulf Of Corinth ◽  
Weather Model ◽  
Point Positioning ◽  
Aperture Radar

Το αντικείμενο της διδακτορικής διατριβής είναι η ανάπτυξη μίας καινοτόμου μεθοδολογίας για την αφαίρεση της τροποσφαιρικής επίδρασης από εφαρμογές διαστημικής γεωδαισίας (GNSS και InSAR), οι οποίες αποτελούν σημαντικά εργαλεία για την παρακολούθηση περιβαλλοντικών παραμέτρων όπου απαιτείται υψηλή ακρίβεια ανίχνευσης (της τάξεως των χιλιοστών του μέτρου), όπως για παράδειγμα η μέτρηση επιφανειακών μετατοπίσεων του φλοιού της γης εξαιτίας τεκτονικών φαινομένων. Η τροπόσφαιρα εισαγάγει μια καθυστέρηση στο ηλεκτρομαγνητικό σήμα, η οποία διορθώνεται μερικώς (μόνο για τα GNSS), με την χρήση εξειδικευμένων τροποσφαιρικών μοντέλων. Επιπροσθέτως, η ατμοσφαιρική διαστρωμάτωση και οι έντονες χωροχρονικές διακυμάνσεις των υδρατμών μέσα σε αυτήν παράγουν ένα πρόσθετο «θόρυβο» στην παραμόρφωση του εδάφους που υπολογίζεται με την μεθοδολογία της συμβολομετρίας (InSAR). Επομένως, η γνώση των τροποσφαιρικών παραμέτρων κατά μήκος του μέσου διάδοσης μπορεί να χρησιμοποιηθεί για τον υπολογισμό και την ελαχιστοποίηση της επίδραση του θορύβου αυτού, έτσι ώστε το εναπομένον σήμα να περιγράφει την παραμόρφωση, ως επί το πλείστον, λόγω τεκτονικών ή άλλων γεωφυσικών διεργασιών. Ο πρωταρχικός στόχος της παρούσας διδακτορικής διατριβής είναι η σύζευξη της κατακόρυφης συνιστώσας των μετρήσεων GNSS υψηλής ακρίβειας (Precise Point Positioning), με τα δεδομένα εξόδου ενός μετεωρολογικού μοντέλου υψηλής ανάλυσης (WRF), ώστε να εξακριβωθεί η εγκυρότητα των αποτελεσμάτων και να παραμετροποιηθεί κατάλληλα το μοντέλο. Ταυτόχρονα, η τρισδιάστατη «τομογραφία» της τροπόσφαιρας που προκύπτει, μας επιτρέπει την ανάκτηση, με μεγαλύτερη ακρίβεια, του συνολικού ποσοστού των υδρατμών στην κατακόρυφη στήλη (Integrated Water Vapor ή IWV) από τα τροποσφαιρικά δεδομένα των μετρήσεων, μετατρέποντας έτσι, δυνητικά, ένα επίγειο δίκτυο δεκτών GNSS σε μετεωρολογικό προγνωστικό εργαλείο. Επιπλέον, η μελέτη επεκτείνεται στην διόρθωση της τροποσφαιρικής επίδρασης σε συμβολογραφήματα από περιοδικές λήψεις InSAR, κατά την ίδια περίοδο, για την περιοχή του Δυτικού Κορινθιακού Κόλπου. Κατ’ αυτόν τον τρόπο, η μεθοδολογία συνδυάζει σημειακές μετεωρολογικές παρατηρήσεις (GNSS) με τρισδιάστατα χωρικά μετεωρολογικά δεδομένα (WRF), για την παραγωγή αναλυτικών χαρτών ζενιθείας τροποσφαιρικής διόρθωσης (ZTD), που χρησιμοποιούνται για την αφαίρεση του θορύβου από τις απεικονίσεις InSAR.

scholarly journals Tropospheric Correction of Sentinel-1 Synthetic Aperture Radar Interferograms Using a High-Resolution Weather Model Validated by GNSS Measurements

2021 ◽  
Vol 13 (12) ◽  
pp. 2258
Author(s):  
Nikolaos Roukounakis ◽  
Panagiotis Elias ◽  
Pierre Briole ◽  
Dimitris Katsanos ◽  
Ioannis Kioutsioukis ◽  
...  
Keyword(s):  
High Resolution ◽  
Synthetic Aperture Radar ◽  
Weather Prediction ◽  
Data Availability ◽  
Synthetic Aperture ◽  
Phase Gradient ◽  
Gulf Of Corinth ◽  
Spatial Coverage ◽  
Gnss Measurements ◽  
Aperture Radar

Synthetic Aperture Radar Interferometry (InSAR) is a space geodetic technique used for mapping deformations of the Earth’s surface. It has been developed and used increasingly during the last thirty years to measure displacements produced by earthquakes, volcanic activity and other crustal deformations. A limiting factor to this technique is the effect of the troposphere, as spatial and temporal variations in temperature, pressure, and relative humidity introduce significant phase delays in the microwave imagery, thus “masking” surface displacements due to tectonic or other geophysical processes. The use of Numerical Weather Prediction (NWP) models as a tropospheric correction method in InSAR can tackle several of the problems faced with other correction techniques (such as timing, spatial coverage and data availability issues). High-resolution tropospheric modelling is particularly useful in the case of single interferograms, where the removal of the atmospheric phase screen (and especially the highly variable turbulent component) can reveal large-amplitude deformation signals (as in the case of an earthquake). In the western Gulf of Corinth, prominent topography makes the removal of both the stratified and turbulent atmospheric phase screens a challenging task. Here, we investigate the extent to which a high-resolution WRF 1-km re-analysis can produce detailed tropospheric delay maps of the required accuracy by coupling its output (in terms of Zenith Total Delay or ZTD) with the vertical delay component in GNSS measurements. The model is operated with varying physical parameterization in order to identify the best configuration, and validated with GNSS zenithal tropospheric delays, providing a benchmark of real atmospheric conditions. We correct sixteen Sentinel-1A interferograms with differential delay maps at the line-of-sight (LOS) produced by WRF re-analysis. In most cases, corrections lead to a decrease in the phase gradient, with average root-mean-square (RMS) and standard deviation (SD) reductions in the wrapped phase of 6.0% and 19.3%, respectively. Results suggest a high potential of the model to reproduce both the long-wavelength stratified atmospheric signal and the short-wave turbulent atmospheric component which are evident in the interferograms.

scholarly journals Integration PS-InSAR and MODIS PWV Data to Monitor Land Subsidence in Semarang City 2015–2018

2019 ◽  
Author(s):  
Reyhan Azeriansyah ◽  
Harintaka .
Keyword(s):  
Water Vapor ◽  
Synthetic Aperture Radar ◽  
Land Subsidence ◽  
Precipitable Water ◽  
Northern Region ◽  
Synthetic Aperture ◽  
Signal Interference ◽  
Interferometric Synthetic Aperture Radar ◽  
Entire Area ◽  
Aperture Radar

Land Subsidence is a slow on set disaster that can be found in coastal areas such as Semarang City. The cause is changing natural conditions and human activities. The observation method that is often done for this phenomenon is GNSS observation. The GNSS observations do not cover the entire area are the disadvantages of this method. Solution that can be used is to use a multi-temporal Interferometric Synthetic Aperture Radar (InSAR) method called Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR). In its application, PS-InSAR has a problem in the form of tropospheric errors that cause signal interference on SAR sensors when making acquisitions that contained in every Synthetic Aperture Radar (SAR) image. MODIS with the NIR band provide Precipitable Water Vapor (PWV) to estimate water vapor levels in the atmosphere. This component can be used in the PS-InSAR in order to eliminate the tropospheric effect on each image so that errors can be minimized and optimize the work of the PS-InSAR method. Based on the value of PS-InSAR before and after tropospheric correction, it is known that the area of Semarang City experienced a rate of land subsidence and the rate of uplift. Land subsidence rate occurs along the northern region, northeast to the east of Semarang City. Uplift rate only occurs in the southeast region due to dumping excavation activities for development and Banjir Kanal Barat due to the river revitalization process. Overall, Semarang City has experienced a land subsidence from 0 to 6.753 cm/year.

scholarly journals MITIGATION ATMOSPHERIC EFFECTS IN INTERFEROGRAM WITH USING INTEGRATED MERIS/MODIS DATA AND A CASE STUDY OVER SOUTHERN CALIFORNIA

2018 ◽  
Vol XLII-3 ◽  
pp. 1799-1803
Author(s):  
X. Wang ◽  
P. Zhang ◽  
Z. Sun
Keyword(s):  
Water Vapor ◽  
Synthetic Aperture Radar ◽  
Atmospheric Water Vapor ◽  
Synthetic Aperture ◽  
Atmospheric Effects ◽  
Interferometric Synthetic Aperture Radar ◽  
Atmospheric Water ◽  
Resolution Imaging ◽  
Aperture Radar

Interferometric synthetic aperture radar(InSAR), as a space geodetictechnology, had been testified a high potential means of earth observation providing a method fordigital elevation model (DEM) and surface deformation monitoring of high precision. However, the accuracy of the interferometric synthetic aperture radar is mainly limited by the effects of atmospheric water vapor. In order to effectively measure topography or surface deformations by synthetic aperture radar interferometry (InSAR), it is necessary to mitigate the effects of atmospheric water vapor on the interferometric signals. This paper analyzed the atmospheric effects on the interferogram quantitatively, and described a result of estimating Precipitable Water Vapor (PWV) from the the Medium Resolution Imaging Spectrometer (MERIS), Moderate Resolution Imaging Spectroradiometer (MODIS) and the ground-based GPS, compared the MERIS/MODIS PWV with the GPS PWV. Finally, a case study for mitigating atmospheric effects in interferogramusing with using the integration of MERIS and MODIS PWV overSouthern California is given. The result showed that such integration approach benefits removing or reducing the atmospheric phase contribution from the corresponding interferogram, the integrated Zenith Path Delay Difference Maps (ZPDDM) of MERIS and MODIS helps reduce the water vapor effects efficiently, the standard deviation (STD) of interferogram is improved by 23 % after the water vapor correction than the original interferogram.

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