A novel phase unwrapping method based on network programming

We present methods and results from interferometric data processing of a long-lasting survey campaign monitoring the Planpincieux glacier, located on the Italian side of the Mont Blanc, using a ground-based synthetic aperture radar (GB-SAR). Monitoring a European Alpine glacier during the winter, when the meteorological conditions are highly variable, presents some difficulties in radar data interpretation. The main issues to tackle in interferometric processing are unwrapping errors and high amplitude dispersion (DA), mainly due to the high velocity and dielectric heterogeneity of the backscattering surface. To improve the reliability of the results, a coherence-driven pixel-selection criterion for identifying the glacier area and a simple approach to reduce possible unwrapping errors in interferograms with low coherence are here proposed. The development of a new 2D polynomial regression model, as a function of elevation, for atmospheric phase screen (APS) estimation is also discussed. A comparison with the results obtained with a vision-based approach gave showed good agreement. ARTICLE HISTORY

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“…As previously mentioned, the first step of the processing consisted of applying a 2D unwrapping algorithm (Costantini 1998).…”

Section: Resultsmentioning

confidence: 99%

“…The first step of the processing chain consists of applying a 2D unwrapping algorithm (Costantini 1998) to all the images. The unwrapping is performed on pixels selected with a coherence-driven criterion (Berardino et al 2002), with the condition γ>0:55; whereγ is the temporal mean coherence.…”

Section: Methodsmentioning

confidence: 99%

Monitoring Alpine glacier surface deformations with GB-SAR

Dematteis

Luzi

Giordan

et al. 2017

Remote Sensing Letters

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“…First, assisted by high-resolution (12 m) TanDEM-X DEM data, all SLC images have been coregistered based on a single master image, which optimizes the geometric and temporal coherence of the interferogram stack. The resampled SLC images were multi-looked by 6 and 14 in range and azimuth directions, respectively, and then used to generate initial interferograms with ground pixel sizes of about 45 m. Then, flat earth and topography phase components from initial interferograms have been removed using TanDEM-X DEM, and the interferograms were unwrapped using the Then, flat earth and topography phase components from initial interferograms have been removed using TanDEM-X DEM, and the interferograms were unwrapped using the Minimum Cost Flow (MCF) method [38]. Also, atmospheric correction to remove stratified tropospheric artifacts that tend to correlate with topography has been done on the interferograms by evaluating linear regression of unwrapped phase with respect to height.…”

Section: Methodsmentioning

confidence: 99%

Modeling Wildfire-Induced Permafrost Deformation in an Alaskan Boreal Forest Using InSAR Observations

et al. 2018

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Abstract:The discontinuous permafrost zone is one of the world's most sensitive areas to climate change. Alaskan boreal forest is underlain by discontinuous permafrost, and wildfires are one of the most influential agents negatively impacting the condition of permafrost in the arctic region. Using interferometric synthetic aperture radar (InSAR) of Advanced Land Observation Satellite (ALOS) Phased Array type L-band Synthetic Aperture Radar (PALSAR) images, we mapped extensive permafrost degradation over interior Alaskan boreal forest in Yukon Flats, induced by the 2009 Big Creek wildfire. Our analyses showed that fire-induced permafrost degradation in the second post-fire thawing season contributed up to 20 cm of ground surface subsidence. We generated post-fire deformation time series and introduced a model that exploited the deformation time series to estimate fire-induced permafrost degradation and changes in active layer thickness. The model showed a wildfire-induced increase of up to 80 cm in active layer thickness in the second post-fire year due to pore-ice permafrost thawing. The model also showed up to 15 cm of permafrost degradation due to excess-ice thawing with little or no increase in active layer thickness. The uncertainties of the estimated change in active layer thickness and the thickness of thawed excess ice permafrost are 27.77 and 1.50 cm, respectively. Our results demonstrate that InSAR-derived deformation measurements along with physics models are capable of quantifying fire-induced permafrost degradation in Alaskan boreal forests underlain by discontinuous permafrost. Our results also have illustrated that fire-induced increase of active layer thickness and excess ice thawing contributed to ground surface subsidence.

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“…Wrapped 32-bit interferogram files were exported to 8-bit image files, and individual pixels were manually modified using a standard raster graphics program so that areas of low coherence or high aliasing were clarified. The clarified 8-bit image was cast back to a 32-bit file, masked to remove problematic zones outside the area of interest, and unwrapped with a standard algorithm (Costantini, 1998). This result was then used to demodulate the original image.…”

Section: Interactive Unwrappingmentioning

confidence: 99%

Evolution of glacier-dammed lakes through space and time; Brady Glacier, Alaska, USA

Capps

Clague

2014

Geomorphology

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Glacier-dammed lakes and their associated jökulhlaups cause severe flooding in downstream areas and substantially influence glacier dynamics. The goal of this dissertation is to identify and characterize the evolution of glacier-dammed lakes in order to predict their future behaviour using ground-truthed remote sensing techniques and dendrochronology. Brady Glacier in southeast Alaska is particularly well suited for a study of these phenomena because it presently dams ten large (> 1 km 2 ) lakes and many smaller ones. This dissertation comprises three studies. First, I used interferometric synthetic aperture radar (InSAR) to identify and characterize three previously unknown subglacial lakes. InSAR allowed me to quantify the vertical displacement and volume of water discharged from the three lakes through time. From the fall of 1995 to the spring of 1996, subsidence ranged from 4 to 26 cm/day and the volume of water discharged ranged from 22,000 ± 2000 to 243,000 ± 14,000 m 3 /day. Subsidence and discharge rates declined significantly during the winter and continued at a lesser rate through March. Second, I used dendrochronology and precise elevation-constrained mapping to date glacially overridden and drowned trees at the glacier margin. Brady Glacier impounded Spur Lake to an elevation of 83 m a.s.l. around AD 1830 and 121 m a.s.l. around 1839. The glacier continued to advance, thickening by at least 77 m between ca. 1844 and 1859 at a site down-glacier of Spur Lake on the opposite glacier margin. Farther down-glacier, North Trick Lake began to form by 1861 and reached its highest elevation at approximately 130 m a.s.l. when Brady Glacier reached its maximum extent around 1880. Third, I georeferenced a variety of maps, airphotos, and optical satellite imagery to characterize the evolution of the glacier and lakes and also created five bathymetric maps. The main terminus of Brady Glacier has changed little since 1880. However, it downwasted at rates of 2-3 m/yr between 1948 and 2000, more than the regional average. The most dramatic retreat (2 km) and downwasting (123 m) occurred adjacent to glacierdammed lakes. These lakes will continue to evolve and play a pivotal role in the evolution of Brady Glacier. If downwasting and retreat continue at rates comparable to the past, the glacier may return to a tidewater regimen and retreat catastrophically until it stabilizes in shallow water.

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A novel phase unwrapping method based on network programming

Cited by 1,178 publications

References 15 publications

Monitoring Alpine glacier surface deformations with GB-SAR

Monitoring Alpine glacier surface deformations with GB-SAR

Modeling Wildfire-Induced Permafrost Deformation in an Alaskan Boreal Forest Using InSAR Observations

Evolution of glacier-dammed lakes through space and time; Brady Glacier, Alaska, USA

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