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Egypt is facing several hazardous environmental phenomena, particularly Sea Level Rise (SLR) and land subsidence. It has been considered to be one of the countries most likely to be affected by SLR because of the low elevation of the Nile Delta region’s northern coastal zone, like all world Deltas. For that, a GIS inundation model has been generated using an original high accuracy local digital elevation model for the Nile Delta region, Egypt (LDEM) and the SLR data measured by the tide-gauges. This model has been used to determine the vulnerable low laying areas to inundation from future SLR in 2050 and to determine land-use types and percentages that are most likely to be affected in the northern Mediterranean coast of Nile Delta region. Finally, a total Hazard Index Map (HIM) has been produced from combining SLR HIM, and the subsidence HIM for the study area which will present the full danger of the two phenomena on the coastal region. The results have shown that the inundated area calculated from the SLR in 2050 model is about 50 km2. From the land-use maps, the areas flooded by the sea represent almost 38.40 km2, 3.80 km2, 5.20 km2, and 2.60 km2 for the urban, agricultural lands, fishing farms, and bare areas, respectively. The authorities and decision makers should pay more attention to the hazardous effects due to the impacts of subsidence and SLR in the Nile Delta region, especially the northern coastal zone. More protection construction such as seawalls and breakwaters should be built at the northern coastal zone of the Nile Delta region vulnerable to inundation of SLR, to prevent the occurrence of the predicted inundation scenarios that could be occurred to this region in the future.

In this contribution, two gravimetric geoid models for Egypt; EGY-LGM2019 and EGY-FGM2019 are developed using the least-squares collocation and the Fast-Fourier Transformation methods, applying Rem...

The “Radio Occultation (RO)” method is one from the simple, accurate and high resolution methods that produces a complete atmosphere model. Each region/country optimizes a “Low Earth Orbiter (LEO)” satellite orbit that covers its climate requirements by processing the “Global Navigation Satellite System (GNSS)” received signal. Orbit optimization includes the six Keplerian parameters that define the orbit shape. The optimum values of the Keplerian parameters are based up on the number and the distribution of the observations located in the country or the case study region. In the present research, a GNSS-LEO orbit optimization is made for Egypt and the Middle East region. The research objective is to feed the case study region by an adequate and uniform distributed number of observations. Both of time and spatial distributions are taken in consideration in deferent orbits comparison. Two GNSS constellations, “Global Positioning System (GPS)” (29 satellites) and “Global Navigation Satellite System (GLONASS)” (24 satellites), data are used in the analysis. More than hundred orbit cases are used for analysis to find the optimum one.Research demonstrated that the proposed orbit parameters for Egypt area are: altitude = 1500 km, inclination = 0°, initial value of mean anomaly = 300° and the other parameters are set to 0 values. The average expected number of observations due to this orbit is 8 observations per day in Egypt. Results also showed that the proposed orbit parameters for Middle East region are: altitude = 1500 km, inclination = 0°, initial value of mean anomaly = 330° and the other parameters are set to 0 values. The average expected number of observations due to this orbit is 854 observations per day in the Middle East region. These orbits insure obtaining the maximum number of observations with the best spatial and time distribution. The only deference between the two orbits is the angle of the initial value of the mean anomaly. If it is set to 300°, the observations distribution is expected to be distorted over the Middle East region by a small value. And if it is set to 330°, the number of observations through Egypt will be reduced to 7 instead of 8 observations per day. Keywords: GNSS, Radio occultation, LEO, Atmosphere, Climatology

This study uses 3600 radiosonde profiles obtained by experimentation from four stations situated in Egypt within 2015–2016 period and Bevis linear regression method was applied to develop a new water vapor weighted temperature (Tm).Bevis, Schueler, Yao, Liou, Suresh Raju and Wayan models performances are assessed using the Tm estimated in this study. The biases of these six models were found to be 4.64 k, 10.12 k, 4.46 k, 4.64 k, 4.14 k and 11.53 k, respectively. Three others radiosonde stations data were used to test the estimated Tm and the above six Tm models, one inside Egypt and two from surrounding areas. The six models are outperformed by the estimated Tm by a root-mean square error of 3.95 k. Therefore Egypt Tm new model’s performance is slightly improved compared to the latter models within RMS of 4.49 k. A final case to develop Tm, Tm model is dividing into groups according to the surface temperature (TS) to improved RMS up to 3.1 K. Last but not least the developed Tm model will be of certain practical value in high-precision Precipitable Water Vapor (PWV) calculation in Egypt. Keywords: Weighted mean temperature (Tm), Radiosonde data, Precipitable water (PW)

Nowadays, a GNSS application is one of the main backbones of lifestyle. The GNSS signal that comes from space satellites to receivers on Earth suffers some delays. The troposphere layer is ...

The gravity field and steady-state ocean circulation explorer (GOCE) satellite mission has provided numerous Global Geopotential Models (GGMs) with different processing methodologies and model accuracies. In the current contribution, the latest releases of GOCE-based GGMs are evaluated on the regional scale using the available terrestrial GPS/Levelling and gravity data collected over Egypt. To overcome the spectral inconsistency between the GOCE-based GGMs and the ground-based data, the spectral enhancement method (SEM) is applied. Five of GOCE-based GGMs have been used, namely GOSG01S, IGGT_R1, IfE_GOCE05s_ GO_CONS_GCF_2_SPW_R5 (SPW_R5 in the following) and NULP-02. The evaluation process of GOCE-based GGMs with the available ground data over Egypt considering the SEM method shows remarkable improvements obtained from the SPW_R5 model. The model provides lower differences of the standard deviations with respect to the EGM2008 and the other applied geopotential gravity models as well as the applied ground-based gravity and GPS/Levelling data. The findings regarding the ground-based data show obvious reductions of about 15.16% and 32.22% achieved by the GOCE-based model in term of standard deviations differences of gravity anomalies and geoid heights, respectively. Therefore, the SPW_R5 model is recommended to be applied as a reference model for compensating the long-to-short wavelength (up to spherical harmonics degree/order 280) components when modelling the gravimetric geoid over Egypt.

It’s essential to find out the delay caused by the troposphere layer to be able to get more accurate results. The precise positioning is very essential for accurate geodetic applications e.g., Crustal deformation and military purposes. The delay is usually modeled as a zenith value and a mapping function to map it to the observed angle. The current research develops a new mapping function model for Egypt through a least square analysis using ten radiosonde stations. The proposed model is a development of Herring continued fraction equation for dry case and wet case separately. The developed model coefficients depend on latitude and day of year. The produced model as well as Niell, Vienna and Chao models are all evaluated using Precise Tropospheric Delay database (PTD). The test data are 36 days over the year 2015 representing winter, spring, summer and fall. The obtained results clearly showed the proposed model is more accurate for Egypt than other models for both dry and wet cases. Keywords: Mapping function, Troposphere, Database, PTD

For space geodetic measurements, estimates of tropospheric delays are highly correlated with site coordinates and receiver clock biases. Thus, it is important to use the most accurate models for the tropospheric delay to reduce errors in the estimates of the other parameters. Both the zenith delay value and mapping function should be assigned correctly to reduce such errors. Several mapping function models can treat the troposphere slant delay. The recent models were not evaluated for the Egyptian local climate conditions. An assessment of these models is needed to choose the most suitable one.The goal of this paper is to test the quality of global mapping function which provides high consistency with precise troposphere delay (PTD) mapping functions. The PTD model is derived from radiosonde data using ray tracing, which consider in this paper as true value.The PTD mapping functions were compared, with three recent total mapping functions model and another three separate dry and wet mapping function model. The results of the research indicate that models are very close up to zenith angle 80°. Saastamoinen and 1/cos z model are behind accuracy. Niell model is better than VMF model. The model of Black and Eisner is a good model. The results also indicate that the geometric range error has insignificant effect on slant delay and the fluctuation of azimuth anti-symmetric is about 1%. Keywords: Tropospheric delay, PTD, Mapping function

The determination of high-resolution geoid for marine regions requires the integration of gravity data provided by different sources, e.g. global geopotential models, satellite altimetry, and shipb...

The space-based GNSS RO technique is a promising tool for monitoring the Earth’s atmosphere and ionosphere (Mousa et al., 2006). The current paper presents the distribution of the occultation event...

Ionospheric delay, can be derived from dual frequency GNSS signals, and then converted into the Vertical Total Electron Contents (VTEC) along the signal path. Various models were devised to calculate VTEC. Examples of such models are the polynomial function model and spherical harmonics model. A common hypothesis of these models is that they are constructed based on the assumption that the entire electron content in the ionosphere is concentrated in a single thin shell at a selected height above Earth. The primary goal of the current research to develop an algorithm capable of producing VTEC maps on an hourly basis, using carrier phase observations from dual frequency GPS receiver. The developed algorithm uses a single GPS station (Zero-difference) to map VTEC over a regional area. The carrier phase measurements are much more precise than the code pseudorange measurements, but they contain an ambiguous term. If such ambiguities are fixed, thence the carrier phase measurements become as unambiguous pseudoranges, but accurate at the level of few millimeters. In current research Sequential Least Square Adjustment (SLSA) was considered to fix ambiguity term in carrier phase observations. The proposed algorithm was written using MATLAB and Called (ZDPID). Two GPS stations (ANKR and BSHM) were used from IGS network to evaluate the developed code, VTEC values were estimated over these two stations. Results of the proposed algorithm were compared with the Global Ionosphere Maps (GIMs), which is generally used as a reference. The results show that the mean difference between VTEC from GIM and estimated VTEC at ANKR station is ranging from −2.1 to 3.67 TECU and its RMS is 0.44. The mean difference between VTEC from GIM and estimated VTEC at BSHM station is ranging from −0.29 to 3.65 TECU and its RMS is 0.38. Another three GPS stations in Egypt were used to generate regional ionosphere maps over Nile Delta, Egypt. The mean differences between VTEC from GIM and estimated VTEC at SAID station is ranging from −1.1 to 3.69 TECU and its RMS is 0.37, from −1.29 to 3.27 TECU for HELW station with RMS equal 0.39, and from 0.2 to 4.2 TECU for BORG station with RMS equal 0.46. Therefore, the proposed algorithm can be used to estimate VTEC efficiently.

The Global Geopotential Models (GGMs) of GOCE (Gravity Recovery and steady- state Ocean Circulation Explorer) differ globally as well as regionally in their accuracy and resolution based on the maximum degree and order (d/o) of the fully normalized spherical harmonic (SH) coefficients, which express each GGM. The main idea of this study is to compare the free-air gravity anomalies and quasi geoid heights determined from several recent GOCE-based GGMs with the corresponding ones from the Earth Gravitational Model 2008 (EGM2008) over Egypt on the one hand and with ground-based measurements on the other hand. The results regarding to the comparison of GOCE-based GGMs with terrestrial gravity and GPS/levelling data provide better improvement with respect to EGM2008. The 4th release GOCE-based GGM developed with the use of space-wise solution strategy (SPW_R4) approximates the gravity field well over the Egyptian region. The SPW_R4 model is accordingly suggested as a reference model for recovering the long wavelength (up to SH d/o 200) components of quasi geoid heights when modelling the gravimetric quasi-geoid over the Egypt. Finally, three types of transformation models: Four-, Five- and Seven-parameter transformations have been applied to reduce the data biases and to provide a better fitting of quasi geoid heights obtained from the studied GOCE-based GGMs to those from GPS/levelling data. These models reveal that the standard deviation of vertical datum over Egypt is at the level of about 32 cm.

An improved hybrid gravimetric geoid model for Egypt, EGY-HGM2016, has been recently computed implementing the least-squares collocation (LSC) method through the remove-compute-restore (RCR) procedure. The computation of EGY-HGM2016 involves different datasets in terms of gravity anomalies determined from the GOCE (gravity field and steady-state ocean circulation explorer)-based global geopotential model (SPW-R4) up to d/o 200 and EGM2008 from d/o 201 to 720 combined with terrestrial gravity datasets in terms of 2140 gravity field anomalies and about 121,480 marine surface gravity anomalies. In addition, orthometric heights from 17 GPS/levelling measurements have been considered during the modelling process to improve the determination of the hybrid gravimetric geoid over the Egyptian region. The EGY-HGM2016 model estimated over Egypt provides geoid heights that are ranging from 7.677 to 21.095 m with a standard deviation (st. dev.) of about 2.534 m in the northwest of the country excluding the involvement of the orthometric heights from GPS/levelling measurements. When the later dataset is considered during the implementation of LSC process, hybrid residual height anomalies ranging from −1.5 to +0.9 m, with a mean of 0.22 m and a st. dev. of 0.17 m, are obtained. Comparison of the predicted hybrid gravimetric geoid with the corresponding ones obtained from EGM2008, GOCE-based SPW R4 model, and GPS/levelling reveals considerable improvements of our EGY-HGM2016 model over Egypt.

Data from the nation-wide GPS continuous tracking network that has been operated by the Geographical Survey Institute of Japan since April 1996 were used to study crustal deformation in the Japanese Islands. We first extracted site coordinate from daily SINEX files for the period from April 1, 1996 to February 24, 2001. Since raw time series of station coordinates include coseismic and postseismic displacements as well as seasonal variation, we model each time series as a combination of linear and trigonometric functions and jumps for episodic events. Estimated velocities were converted into a kinematic reference frame [Heki, K., 1996. Horizontal and vertical crustal movements from three-dimensional very long baseline interferometry kinematic reference frame: implication for reversal timescale revision. J. Geophys. Res., 101: 3187–3198.] to discuss the crustal deformation relative to the stable interior of the Eurasian plate. A Least-Squares Prediction technique has been used to segregate the signal and noise in horizontal as well as vertical velocities. Estimated horizontal signals (horizontal displacement rates) were then differentiated in space to calculate principal components of strain. Dilatations, maximum shear strains, and principal axes of strain clearly portray tectonic environments of the Japanese Islands. On the other hand, the interseismic vertical deformation field of the Japanese islands is derived for the same GPS data interval. The GPS vertical velocities are combined with 31 year tide gage records to estimate absolute vertical velocity. The results of vertical deformation show that (1) the existence of clear uplift of about 6 mm/yr in Shikoku and Kii Peninsula, whereas pattern of subsidence is observed in the coast of Kyushu district. This might reflect strong coupling between the Philippine Sea plate and overriding plate at the Nankai Trough and weak coupling off Kyushu, (2) no clear vertical deformation pattern exists along the Pacific coast of northeastern Japan. This might be due to the long distance between the plate boundary (Japan trench) and overriding plate where GPS sites are located, (3) significant uplift is observed in the southwestern part of Hokkaido and in northeastern Tohoku along the Japan Sea coast. This is possibly due to the viscoelastic rebound of the 1983 Japan Sea (Mw 7.7) and the 1993 Hokkaido–Nansei–Oki (Mw 7.8) earthquakes and/or associated with distributed compression of incipient subduction there. We then estimate the elastic deformation of the Japanese Islands caused by interseismic loading of the Pacific and Philippine Sea subduction plates. The elastic models account for most of the observed horizontal velocity field if the subduction movement of the Philippine Sea Plate is 100% locked and if that of the Pacific Plate is 70% locked. However, the best fit for vertical velocity ranges from 80% to 100% coupling factor in southwestern Japan and only 50% in northeastern Japan. Since horizontal data does not permit the separation of rigid plate motion and interplate coupling because horizontal velocities include both contributions, we used the vertical velocities to discriminate between them. So, we can say there is strong interplate coupling (80%–100%) over the Nankaido subduction zone, whereas it is about 50% only over the Kurile–Japan trench.

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Global Positioning System (GPS) measurements were made to estimate the crustal deformation strain rate for the Deccan trap region, western India. Estimated horizontal velocity vectors in ITRF96 are in the range of 40–60 mm/yr with an average of 51 mm/yr in N47°E. Using the horizontal components of the velocity vectors, strain field has been estimated by the Least Square Prediction (LSP) method. An extension is observed along the west coast and south of Koyna and Warna reservoirs, transcending in to a region of compressive regime towards the interior of the shield area. The west coast geothermal province coincides with the extension regime. The collision between India and Eurasia is likely cause for compression regime. The results are discussed in conjunction with the seismo-tectonics of the study region.

As a part of the earthquake prediction project in the Tokai district, levelling observations are being carried out four times a year in the Omaezaki peninsula. To analyze this time dependent data, an adjustment method in which the velocity of vertical motions, the amplitude and phase of annual variation of each benchmark are assumed to be unknown is applied. The main results of the analysis are summarized as follows: (1) at reference time 1981.0, the average phase of benchmarks along the levelling route between Kakegawa city and Omaezaki is about 21 degree, (2) at BM140-1 (Kakegawa), relative to BM92305 (Omaezaki) the maximum amplitude of one-year period variation is about 7.55 mm, i.e., the difference between the top and bottom of wave movement may reach 15.1 mm, and (3) the subsidence rate on the levelling route from BM140-1 to BM92305 decreases gradually as the benchmark is farther from the fixed point BM92305 with the maximum subsiding rate of 7.7 mm/yr. The estimated rates of vertical deformation (i.e., after removing the seasonal variation) are inverted to estimate interplate coupling between the subducting Philippine Sea plate and the overriding continental plate. This facilitates understanding of the strain accumulation process in this complicated region. The results indicate that there is a high coupled region extending from 7 to 27 km deep, the maximum back-slip rate in this region reaches 27 mm/yr, and the direction of the plate convergence at the Suruga Trough is N 54°W ± 5°.

Data from the nationwide GPS continuous tracking network, which has been operated by the Geographical Survey Institute (GSI) of Japan since April 1996, were used to study crustal deformation in the Shikoku district, Japan. The crustal deformation data are inverted to estimate interplate coupling between the subducting Philippine Sea (PHS) plate and the overriding continental plate. For this purpose, we first extracted site coordinates from daily SINEX files for the period from 1 April 1996 to 31 March 1998, and estimated average site velocities by linear regression. Estimated velocities under ITRF96 are converted into a kinematic reference frame [K. Heki, J. Geophys. Res. 101 (1996) 3187–3198] to discuss the crustal deformation relative to the stable interior of the Eurasian (EUR) plate. To segregate the signal and noise in the thus obtained velocity vectors, we employed the least-squares prediction technique. Estimated signals (displacement vectors) were used to reconstruct the strains (dilatations, maximum shear strains, principal axes of strains) and to estimate the interplate coupling in the area. Results of crustal strains clearly portray tectonic straining of the Shikoku island: (1) dilatational strains show that the Shikoku island is under a compressive strain regime induced by the subducting PHS plate; (2) maximum shear is high in the island, which may be due to the oblique subduction; (3) the principal axes of the strains indicate that the Shikoku island is under the influence of the converging oceanic plate beneath the island. In contrast, the results of the inversion analysis show: (1) there is a high coupled region extending from 10 to 30 km deep; (2) the average back slip rate in this region reaches 43±5 mm/yr; and (3) the direction of the plate convergence at the Nankai trough is N42±6°W.

Least-squares prediction using two empirically deduced local covariance functions was applied to estimate the horizontal strains in the Tohoku district, Japan. The horizontal displacement vectors that cover the area of approximately 450×275 km 2 for the interval from 1979 to 1991 were used and the results were shown in the form of contour maps. In order to apply least-squares prediction for studying the horizontal strains, we first derived two covariance functions of the horizontal crustal movements, one for the E–W component and the other for the N–S component, with a Gaussian form. Then we used these functions to estimate the spatial distribution of the horizontal strains in the Tohoku district. By the present method, the results of numerical calculation are discussed with reference to the tectonics of the Tohoku district. The main conclusions are:1. The total amount of strain accumulation thus obtained does not exceed 3×10 −6 in every part of the district except the North Japan Sea coast and the area at the central part of Tohoku. We may roughly say, therefore, that the average rate of strain accumulation is mostly less than the order of 0.25×10 −6 ⧹a, but it is not certain whether the rate is constant or not.2. The general pattern of distribution of principal axis of strain in the Tohoku district shows compression in ESE–WNW direction.3. Comparison of the above estimated geodetic strain rates with the ones estimated by ( Kaizuka and Imaizumi, 1984 ) from fault data in the Quaternary period shows that the former is one order of magnitude higher than the latter.

Data from the nationwide continuous GPS network, operated by the Geographical Survey Institute of Japan, were used to estimate crustal strains in the Japanese islands. We used horizontal velocity vectors at 610 sites for the period April, 1996 to March, 1997, and employed the Least Squares Prediction method to interpolate the velocities to a uniform 7km × 7km grid over Japan. The gridded velocities were then differentiated in space to calculate principal components of strains. Results clearly portray tectonic strainings of the Japanese islands in one year; (1) Dilatational strains show that the Japanese islands are under a compressive strain regime induced by the subducting oceanic plates, (2) Distribution of high maximum shear strains coincides with the regions of crustal activities, and (3) Principal axes of the strains indicate influences of E-W and NW-SE compression due to the converging oceanic plates. North-south extension in Kyushu is also visible.

Least-squares prediction using an empirically deduced local covariance function was performed to investigate the temporal change in the rates of vertical crustal movements in the Tohoku district, Japan. Levelling data covering an area of approximately 450 × 275 km2 observed between 1966 and 1995 were used and the results shown in the form of contour maps. Firstly we derived a covariance function of the rates of vertical crustal movement with a Gaussian form function. We used this function to estimate the spatial distribution of the rates of vertical crustal movements. By the present method, a steady tilt of the Tohoku district to the east, toward the Japan Trench and an areal uplift in the southwestern part were well reproduced. Moreover, a significant temporal change in vertical movement rates is clearly seen.

To estimate the elastic and inelastic strains in the Japanese Islands, we used horizontal velocity vectors at 917 sites of the nation-wide GPS network for the period April 1996 to March 1998. To segregate the signal and noise in the velocity vectors, we employed the Least-Squares Prediction technique (LSP). Estimated signals (displacement vectors) were differentiated in space to reconstruct the total strains (elastic plus inelastic). Then, we estimated inelastic strains of the islands using the inversion method introduced by Hori et al. (1999). The estimated rate of inelastic strains is of the order of 10−3 μstrains/yr. Compared this with the rate of total strains of the order of 0.1 μstrains/yr, inelastic part was found to be negligible. Finally, shear stresses at the surface of the Japanese Islands have been estimated, based on the elasticity theory.