The co-registration begins with obtaining the DEM in SAR coordinates followed by the matching algorithm and the spectral diversity method which includes considering the interferometric phase applied over the overlapping areas of the bursts. The space component is intended to provide free of charge easily accessible data for registered users [ 5 ]. best site to buy a research paper pdf First, the resolution of Sentinel-1 IW images in the azimuth direction is four times worse than in the range direction.
In the case of the Trinity Glacier, the underlying reason is the strong surface velocity gradients that deform the surface features e. However, their approach considered the use of all azimuth and range velocity components solving by least-squares, while our approach discards the azimuth offsets from the estimation to avoid undesired ionospheric effects and, simultaneously, to avoid Sentinel-1 shortcomings such as its lower azimuth resolution. buy custom paper online wristbands This type of SAR acquisition implies the antenna steering from aft to fore during burst acquisition leading to an azimuth variant Doppler centroid [ 9 ], which is corrected with a deramping operation of the Doppler spectrum.
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Offset tracking, on the contrary, is capable of capturing these type of velocity gradients, making this methodology especially useful to retrieve region-wide surface velocity fields. New Smart Spell Checker. Similarly, for Ekblaw Glacier, both our results and those of van Wychen et al. These relations are given in Equation 2 below, where the matrix form is also displayed: The offset-tracking technique, in turn, proves to be more useful for fast-flowing glaciers.
The comparison between methodologies illustrates the difficulties of MCF to resolve the velocity field of a few tongues from the western glaciers of the POW Icefield. Open Access This article is freely available re-usable Remote Sensing , 9 5 , ; doi: Supplementary Materials The following are available online at www.
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It is precisely this fine resolution that allows us to discern the ice divide between the eastern and western flowing glaciers Figure S2. On the other hand, the method failed to work in areas with strong velocity gradients and areas of fast glacier movement e. writing a letter of recommendation for customer service After a full co-registration is achieved, a deramping of the SLC images for correcting the azimuth phase ramp is required to apply oversampling in the offset tracking procedures [ 49 ].
The aim of the paper is to show the performance of the Sentinel-1 SAR Single Look Complex SLC Interferometric Wide-swath level-1 product with a nominal resolution of 5 and 20 m in the across- and along-track directions, respectively for retrieving glacier surface velocities using offset tracking and differential interferometry D-InSAR techniques. A StyleWriter edition to suit your budget and writing needs. report writing help good lab Finally, many research papers indicate a clear increase in ice mass losses and associated contribution of Canadian Arctic glaciers to sea-level rise during recent years.
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This approach would allow for obtaining surface velocity fields within featureless accumulation areas, while avoiding the ionospheric effects typical of Arctic and Antarctic areas [ 21 ]. We can observe how the northern component of the velocity increases and decreases depending on the direction of glacier flow. The recently deployed Sentinel-1B satellite will improve the interferometric capabilities of the Sentinel-1 constellation by reducing the de-correlation and the amount of movement between consecutive acquisitions [ 12 ].
The different nature and dynamics of these glaciers, together with the presence of wide ice-free areas which allows performing a finer co-registration between acquisitions makes this location optimal to test and apply different SAR surface velocity estimation methodologies. This type of SAR acquisition implies the antenna steering from aft to fore during burst acquisition leading to an azimuth variant Doppler centroid [ 9 ], which is corrected with a deramping operation of the Doppler spectrum. The velocity maps are overlaid on top of Sentinel-1 SAR images taken between 10 and 17 February
Moreover, offset tracking is less affected by de-correlation than differential interferometry. This makes it difficult to give a proper error estimate. Furthermore, we see a possible application of the ascending and descending passes to speckle tracking. We exclusively applied the intensity offset tracking algorithm.