Figure 4 - uploaded by El Hachemi Bouali
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Three Components of a Complex Number: In-Phase, Quadrature, and Phase Incoming radar wave information is detected and stored as a complex number. This requires the quantification of both magnitude (amplitude) and phase measurements. The digital representation of SAR data includes a real, in-phase (I) component and an imaginary, quadrature (Q) component. The phase is the angle measured between I and Q components (ESA, 2012b).
Source publication
The Nile Delta in Egypt is being threatened by two continuous and relatively slow hazards: encroachment from the Mediterranean Sea as sea levels rise and land subsidence of the delta itself. The magnitude of sea level rise has been actively monitored, while the subsidence of the Nile Delta has not been adequately quantified spatially and temporally...
Contexts in source publication
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... of when peak aerosol concentration occurs, both studies ( Favez et al., 2008;El-Askary & Kafatos, 2008) conclude that aerosol levels are relatively high throughout the entire year throughout the Nile Delta. Both atmospheric spatial (lateral) and temporal variations in aerosol concentrations are also observed (Figure 24). measurements, in terms of the Nile Delta, would appear to be greater than actual rates obtained via field measurements. ...
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... size, and abundance of each type of aerosol scatter radar waves differently. Figure 24 shows the high lateral and temporal variability of the AOD and fine mode fraction (FMF) across the Nile Delta. The use of radar interferometry becomes much more difficult over areas where atmospheric effects (and phase changes) completely differ between locations within one cropped area. ...
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... 39 shows the distribution of subsidence rates superimposed on the annual domestic and industrial water demand by governorate, from Figure 39. Figure 40 shows the general trend of groundwater extraction rates observed in 1992, which is that extraction rates increase southward, for many reasons: (1) the largest city in Egypt (Cairo) is located at the southern tip of the Nile Delta, (2) the delta transitions to more arid regions toward the south and the only source of water is groundwater, and (3) rainfall amounts decrease away from the Mediterranean Sea. Groundwater extraction rates taken from RIGW, et al. (1992). ...
Citations
... Numerous studies have recorded the vertical land subsidence velocities of the Nile Delta by using in situ observations [23,26,[28][29][30][31][32] as well as remote sensing techniques [15,19,[33][34][35][36][37][38][39][40]. Across the northern Delta, about 87 continuous sediment drill cores from the National Museum of Natural History (NMNH) of the Smithsonian Institution were used to provide estimates of its subsidence [41]. ...
... In recent years, a number of researchers have been interested in measuring land subsidence rates in the Nile Delta region by using radar interferometric techniques [15,19,31,38,39,43]. However, most The second estimation of the displacement using the Small Baseline Subset (SBAS) technique [11] was performed to recover the final processed displacement time series from the atmospheric artifacts, taking into account a coherence threshold applied to the input stack of the unwrapped phase ( Figure 10). ...
... In recent years, a number of researchers have been interested in measuring land subsidence rates in the Nile Delta region by using radar interferometric techniques [15,19,31,38,39,43]. However, most The deformation component can be isolated from the non-deformation component by addressing phase noise due to changing scattering properties over time. ...
The accurate detection of land subsidence rates in urban areas is important to identify damage-prone areas and provide decision-makers with useful information. Meanwhile, no precise measurements of land subsidence have been undertaken within the coastal Port-Said City in Egypt to evaluate its hazard in relationship to sea-level rise. In order to address this shortcoming, this work introduces and evaluates a methodology that substantially improves small subsidence rate estimations in an urban setting. Eight ALOS/PALSAR-1 scenes were used to estimate the land subsidence rates in Port-Said City, using the Small BAse line Subset (SBAS) DInSAR technique. A stereo pair of ALOS/PRISM was used to generate an accurate DEM to minimize the residual topography effect on the generated interferograms. A total of 347 well distributed ground control points (GCP) were collected in Port-Said City using the leveling instrument to calibrate the generated DEM. Moreover, the eight PALSAR scenes were co-registered using 50 well-distributed GCPs and used to generate 22 interferogram pairs. These PALSAR interferograms were subsequently filtered and used together with the coherence data to calculate the phase unwrapping. The phase-unwrapped interferogram-pairs were then evaluated to discard four interferograms that were affected by phase jumps and phase ramps. Results confirmed that using an accurate DEM (ALOS/PRISM) was essential for accurately detecting small deformations. The vertical displacement rate during the investigated period (2007-2010) was estimated to be -28 mm. The results further indicate that the northern area of Port-Said City has been subjected to higher land subsidence rates compared to the southern area. Such land subsidence rates might induce significant environmental changes with respect to sea-level rise.
