Abstract

The present study is aimed at investigating the potentialities of the COSMO/SkyMed (CSK) constellation for ground elevation measurement with particular attention devoted to the impact of the improved spatial resolution wrt the previous SAR sensors.Assuming no movement and successful orbital error removal, the main problem in height computation derives from the atmospheric artifacts (APS). Different strategies can be adopted to filter out this signal:1.By processing stack of images and through advanced multi-temporal interferometric analysis, it is possible to infer with sub-metric precision the height of targets which behave coherently in time (persistent scatterers). These techniques allow to filter out the atmospheric signal thanks to its decorrelation in time and correlation in space. The main drawback is related to the availability of coherent scatterers on the scene. High resolution sensors (as CSK) allow to increase the density of the measurable targets.2.By using tandem-like high resolution interferometric pairs and a reference low resolution DEM, it is possible to filter the differential phase field in order to remove the atmospheric artifacts. The filtered InSAR phase may hence improve the accuracy of the original DEM. 3.Through Numerical Weather Models (NWM), it is possible to estimate the InSAR phase related to the interaction between microwave and atmosphere.In the present work we explored all the mentioned strategies for APS mitigation. The selected test site was Parkfield (California, USA), where a consistent number of both Stripmap HIMAGE and Enhanced Spotlight right-descending HH acquisitions are available with very close incidence angles. Both dataset were hence used to experiment the reliability of multi temporal analysis for height computation (strategy 1). Our results are in line with indications found in recent literature, proving the potential of PSI to provide sub-metric precision of height measurements. Satisfactory performances may be achieved also by properly filtering the differential interferometric phase derived by using CSK tandem-like pairs (strategy 2). In particular, when normal the baselines exceed 300 m, it is possible to derive DEMs fulfilling the HRTI Level 3 specifications on the relative vertical accuracy. On the contrary, the mitigation of atmospheric artifacts through NWM (strategy 3) is still uncertain especially for X-band InSAR. Our preliminary results confirm the indications coming from other similar studies: NWM are effective for the long wavelengths (>20 km) and for vertical stratification which depends on the hydrostatic component of the troposphere, while, when dealing with the turbulent component of the low troposphere, this approach is unfeasible. SAR processing indeed requires millimetric accuracy in the zenith atmospheric delay while the outcomes of the NWM are in the order of centimeters, as confirmed by the validation performed through independent RAOBS and GPS ZTD data.

Autore Pugliese

• Bovenga Fabio

Tutti gli autori

• D. O. Nitti; F. Bovenga

Titolo volume/Rivista

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Anno di pubblicazione

2012

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Settori ERC

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