Global Geopotential Models (GGMs) may contain long-wavelength errors due to difficulties in colle... more Global Geopotential Models (GGMs) may contain long-wavelength errors due to difficulties in collecting and using global heterogeneous gravity data, which further degrades the quality of regional gravity field modelling. In this study, satellite-only and high degree reference geopotential models denoted as GOCO05s and EGM2008, respectively, have been tailored (refined) to fit the gravity data in Egypt using integral formulas in order to select the optimal model that can be used for the reference gravity field model for the Egyptian territory. The results show that the tailored model of EGM2008 denoted as EGTM0817 is the one that gives better results in Egypt than the other tailored model of GOCO05s denoted as E G TGOC5s, where the mean value, the standard deviation and the range of the reduced gravity anomalies to EGTM0817 compared with EGTGOC5s have lesser values by about 80%, 30%, and 21%, respectively.
We present a case of migrating copper-T intrauterine contraceptive device (IUCD) into the bowel w... more We present a case of migrating copper-T intrauterine contraceptive device (IUCD) into the bowel wall at the recto-sigmoid junction, and the colonoscopic retrieval of the device. This case introduces the possibility of safe rectal retrieval of migrating IUCD implanted into the bowel wall.
It has been a long time for the navy research centers to do great efforts and concentrate their r... more It has been a long time for the navy research centers to do great efforts and concentrate their researches in developing the used methods for measuring the depths, and increasing their efficiency even this developing is to the traditional methods, or to the remote sensing technique. Due to the presence of the river Nile as a navigational route in Egypt passing from its south to its north, the remote sensing technique was used in this research for measuring the depths, by using multi-spectral band satellite image with resolution 1.65m, which covers an area of almost 15.52 Km²of the river Nile (of width=1Km and length=15.52Km) from Esna to Nagaa Hamadii, the image was corrected geometrically, and The radiances were corrected from all of the effective errors. The mathematical equations were used to calculate the reflectance values from the corrected radiance values. From the obtained reflectance, the depths were computed, by using suitable mathematical model. The data analysis mainly d...
Abstract
The fixed stations of a geodetic network are continuously changing, due to the change o... more Abstract
The fixed stations of a geodetic network are continuously changing, due to the change of its tectonic plate. When the instantaneous coordinates of the stations at any epoch are needed, the velocity of the stations should be known. The velocity of any station is determined by two techniques, firstly by using the time series of GPS observation and secondly by using the created velocity model of plate which obtained from the plate Cartesian rotation vector. In this research, using the available number of the permanent GPS stations made by the Egyptian National Research Institute of Astronomy and Geophysics (ENRIAG) to obtain the two velocity models of Nubian-plate ITRF2008 for year 2011 and 2013. Using the High Accuracy Reference Network (HARN) stations after transforming them from ITRF94 epoch 1996.0 into ITRF08 epoch 1996.0 to check the two local models by determining the velocities at all stations. The maximum difference in velocities between these models is found within ±0.2 cm. Therefore we took the mean of the two local models to create the best fit local velocity model. Additionally we used the HARN network and permanent GPS stations to assess the local velocity model with the velocity model of Nubian-plate ITRF08 which created by the IGS stations, the maximum difference between them is found within ±0.14cm. From the results, the velocities obtained at all permanent stations by processing the time series of GPS observations are changing yearly while the velocity model gives constant velocity for each station yearly. Nevertheless, the velocity vector length which obtained by the local velocity model is closest to the velocity vector length which obtained by GPS processing when increasing the time difference between the GPS sessions , this is appear in HARN station (0Z17) where the difference in velocity vector length is 0.5 mm at 17.14 years. Finally we created a computer program to compute the HARN stations at any epoch on ITRF08 by using the local velocity model and the transformation parameters between ITRF94 and ITRF08.
Abstract:
Recently, several high and ultra-high degree global harmonic models have been develope... more Abstract: Recently, several high and ultra-high degree global harmonic models have been developed. They are typically used in local gravity field modeling via the remove- restore technique, in order to establish accurate and precise local geoid solutions. In the current study, a comparison is performed, concerning Egypt, among the behaviors of the new harmonic models EGM96, GFZ97 and GPM98C with respect to the available local data. These comparisons ascertain that none of these new models recover the long-medium spectral information in a reliable manner, due to the absence of the Egyptian local data during the global solutions for those harmonic models. Among the three investigated harmonic models, the EGM96 model, as a reference field, seems to perform slightly better than the other two models, based on the available Egyptian data set. So, it is recommended to improve the EGM96 model, using the local Egyptian data.
ABSTRACT
New additional Global Geopotential Models [GGMs] have now been released into the public... more ABSTRACT New additional Global Geopotential Models [GGMs] have now been released into the public domain, those including data from the CHAMP, GREACE and GOCE dedicated satellite gravimetric mission. Those satellite tracking data have resolved the long wave length component of the global gravity field with rather very high accuracy [10]. ---------------------------------------------------------------------------------------------------- ----- 2013, Civil Engineering Research Magazine CERM, Vol. 35 .No. (3), Published by Faculty of Engineering, Al-Azhar University, Cairo, Egypt.
Therefore, it is important to evaluate those new models over Egypt to determine which; of them is the most appropriate GGM there. In this study a comparison of the performance of three of the GGMs released between 1996 tell now (EGM96, EGM2008 and EIGEN-6C 2011) over Egypt is made. The gravity anomalies computed from the models are compared with point free air gravity anomalies on land. The results have indicated the outstanding performance of EGM2008 to the other examined GGMs undoubtedly. EGM2008 has1.23 times better statistics than the EGM96 and 2.54 times than EIGEN-6C 2011, in terms of root mean square error [r.m.s.e].
1- Abstract:
In the current study, 5'x5' grid values of geoidal heights, for the whole terri-tory... more 1- Abstract: In the current study, 5'x5' grid values of geoidal heights, for the whole terri-tory of Egypt were computed by collocation technique, based on all the old and the recent available heterogeneous geodetic data. The well-known remove-restore technique was used for the purpose of maximally smoothing the used data as a pre-request by the collocation method. This was done, for the first time in Egypt, by the aid of an appropriate high degree global harmonic model, tailored to the local terrestrial data. A digital terrain model for Egypt was also used for the same purpose. The final results have shown a rather good internal and external accu-racy of the predicted geoid of about 0.22 m and 0.63 m respectively.
Global Geopotential Models (GGMs) may contain long-wavelength errors due to difficulties in colle... more Global Geopotential Models (GGMs) may contain long-wavelength errors due to difficulties in collecting and using global heterogeneous gravity data, which further degrades the quality of regional gravity field modelling. In this study, satellite-only and high degree reference geopotential models denoted as GOCO05s and EGM2008, respectively, have been tailored (refined) to fit the gravity data in Egypt using integral formulas in order to select the optimal model that can be used for the reference gravity field model for the Egyptian territory. The results show that the tailored model of EGM2008 denoted as EGTM0817 is the one that gives better results in Egypt than the other tailored model of GOCO05s denoted as E G TGOC5s, where the mean value, the standard deviation and the range of the reduced gravity anomalies to EGTM0817 compared with EGTGOC5s have lesser values by about 80%, 30%, and 21%, respectively.
We present a case of migrating copper-T intrauterine contraceptive device (IUCD) into the bowel w... more We present a case of migrating copper-T intrauterine contraceptive device (IUCD) into the bowel wall at the recto-sigmoid junction, and the colonoscopic retrieval of the device. This case introduces the possibility of safe rectal retrieval of migrating IUCD implanted into the bowel wall.
It has been a long time for the navy research centers to do great efforts and concentrate their r... more It has been a long time for the navy research centers to do great efforts and concentrate their researches in developing the used methods for measuring the depths, and increasing their efficiency even this developing is to the traditional methods, or to the remote sensing technique. Due to the presence of the river Nile as a navigational route in Egypt passing from its south to its north, the remote sensing technique was used in this research for measuring the depths, by using multi-spectral band satellite image with resolution 1.65m, which covers an area of almost 15.52 Km²of the river Nile (of width=1Km and length=15.52Km) from Esna to Nagaa Hamadii, the image was corrected geometrically, and The radiances were corrected from all of the effective errors. The mathematical equations were used to calculate the reflectance values from the corrected radiance values. From the obtained reflectance, the depths were computed, by using suitable mathematical model. The data analysis mainly d...
Abstract
The fixed stations of a geodetic network are continuously changing, due to the change o... more Abstract
The fixed stations of a geodetic network are continuously changing, due to the change of its tectonic plate. When the instantaneous coordinates of the stations at any epoch are needed, the velocity of the stations should be known. The velocity of any station is determined by two techniques, firstly by using the time series of GPS observation and secondly by using the created velocity model of plate which obtained from the plate Cartesian rotation vector. In this research, using the available number of the permanent GPS stations made by the Egyptian National Research Institute of Astronomy and Geophysics (ENRIAG) to obtain the two velocity models of Nubian-plate ITRF2008 for year 2011 and 2013. Using the High Accuracy Reference Network (HARN) stations after transforming them from ITRF94 epoch 1996.0 into ITRF08 epoch 1996.0 to check the two local models by determining the velocities at all stations. The maximum difference in velocities between these models is found within ±0.2 cm. Therefore we took the mean of the two local models to create the best fit local velocity model. Additionally we used the HARN network and permanent GPS stations to assess the local velocity model with the velocity model of Nubian-plate ITRF08 which created by the IGS stations, the maximum difference between them is found within ±0.14cm. From the results, the velocities obtained at all permanent stations by processing the time series of GPS observations are changing yearly while the velocity model gives constant velocity for each station yearly. Nevertheless, the velocity vector length which obtained by the local velocity model is closest to the velocity vector length which obtained by GPS processing when increasing the time difference between the GPS sessions , this is appear in HARN station (0Z17) where the difference in velocity vector length is 0.5 mm at 17.14 years. Finally we created a computer program to compute the HARN stations at any epoch on ITRF08 by using the local velocity model and the transformation parameters between ITRF94 and ITRF08.
Abstract:
Recently, several high and ultra-high degree global harmonic models have been develope... more Abstract: Recently, several high and ultra-high degree global harmonic models have been developed. They are typically used in local gravity field modeling via the remove- restore technique, in order to establish accurate and precise local geoid solutions. In the current study, a comparison is performed, concerning Egypt, among the behaviors of the new harmonic models EGM96, GFZ97 and GPM98C with respect to the available local data. These comparisons ascertain that none of these new models recover the long-medium spectral information in a reliable manner, due to the absence of the Egyptian local data during the global solutions for those harmonic models. Among the three investigated harmonic models, the EGM96 model, as a reference field, seems to perform slightly better than the other two models, based on the available Egyptian data set. So, it is recommended to improve the EGM96 model, using the local Egyptian data.
ABSTRACT
New additional Global Geopotential Models [GGMs] have now been released into the public... more ABSTRACT New additional Global Geopotential Models [GGMs] have now been released into the public domain, those including data from the CHAMP, GREACE and GOCE dedicated satellite gravimetric mission. Those satellite tracking data have resolved the long wave length component of the global gravity field with rather very high accuracy [10]. ---------------------------------------------------------------------------------------------------- ----- 2013, Civil Engineering Research Magazine CERM, Vol. 35 .No. (3), Published by Faculty of Engineering, Al-Azhar University, Cairo, Egypt.
Therefore, it is important to evaluate those new models over Egypt to determine which; of them is the most appropriate GGM there. In this study a comparison of the performance of three of the GGMs released between 1996 tell now (EGM96, EGM2008 and EIGEN-6C 2011) over Egypt is made. The gravity anomalies computed from the models are compared with point free air gravity anomalies on land. The results have indicated the outstanding performance of EGM2008 to the other examined GGMs undoubtedly. EGM2008 has1.23 times better statistics than the EGM96 and 2.54 times than EIGEN-6C 2011, in terms of root mean square error [r.m.s.e].
1- Abstract:
In the current study, 5'x5' grid values of geoidal heights, for the whole terri-tory... more 1- Abstract: In the current study, 5'x5' grid values of geoidal heights, for the whole terri-tory of Egypt were computed by collocation technique, based on all the old and the recent available heterogeneous geodetic data. The well-known remove-restore technique was used for the purpose of maximally smoothing the used data as a pre-request by the collocation method. This was done, for the first time in Egypt, by the aid of an appropriate high degree global harmonic model, tailored to the local terrestrial data. A digital terrain model for Egypt was also used for the same purpose. The final results have shown a rather good internal and external accu-racy of the predicted geoid of about 0.22 m and 0.63 m respectively.
The aim of this research is to develop a new precise and high-resolution geoid model for Egypt by... more The aim of this research is to develop a new precise and high-resolution geoid model for Egypt by refining the Global Geopotential Models (GGMs) through a process named tailoring, where the existing spherical harmonic coefficients of geopotential model are fitted to the Egyptian gravity field by integral formulas using an iterative algorithm to improve the accuracy of the obtained harmonic coefficients. The satellite-only model GOCO05s (complete to degree and order 280) and ultra-high degree geopotential model EGM2008 (complete to degree and order 2190) have been tailored to the Egyptian 5′×5′ mean gravity anomalies in order to select the optimal model that can be used for the reference gravity field for the new geoid model. The results show that both EG1GOC5s and EGTM0818 tailored geopotential models give less and better residual gravity anomalies, where the EGTM0818 tailored model has been improved significantly by about 27% than the EGM2008 model similarly, the EG1GOC5s tailored model better than the GOCO05s model by about 17%. Gravimetric and combined (gravity and astrogeodetic data) geoids solutions for Egypt have been computed using both tailored geopotential models in the remove-restore technique through Least-squares Collocation (LSC). The computed geoids are fitted to the GPS/levelling stations. The results show that no significant variance between the gravimetric and combined geoids solutions exists. In addition, both combined geoids solutions are given the same accuracy, where RMS ≈ ± 15 cm. Finally, a comparison between GPS/levelling stations and both NGRAV-A and NGRAV-B gravimetric geoids computed by using both EG1GOC5s and EGTM0818 models, respectively, give nearly the same external accuracy, where the RMS of the differences ± 13 cm for NGRAV-A and ± 15 cm for NGRAV-B. Therefore, we recommend that both tailored geopotential models as reliable models for geoid heights over Egypt.
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Papers by Maher M Amin
The fixed stations of a geodetic network are continuously changing, due to the change of its
tectonic plate. When the instantaneous coordinates of the stations at any epoch are needed, the
velocity of the stations should be known. The velocity of any station is determined by two
techniques, firstly by using the time series of GPS observation and secondly by using the created
velocity model of plate which obtained from the plate Cartesian rotation vector. In this research,
using the available number of the permanent GPS stations made by the Egyptian National Research
Institute of Astronomy and Geophysics (ENRIAG) to obtain the two velocity models of Nubian-plate
ITRF2008 for year 2011 and 2013.
Using the High Accuracy Reference Network (HARN) stations after transforming them from ITRF94 epoch
1996.0 into ITRF08 epoch 1996.0 to check the two local models by determining the velocities at all
stations. The maximum difference in velocities between these models is found within ±0.2 cm.
Therefore we took the mean of the two local models to create the best fit local velocity model.
Additionally we used the HARN network and permanent GPS stations to assess the local velocity model
with the velocity model of Nubian-plate ITRF08 which created by the IGS stations, the maximum
difference between them is found within ±0.14cm.
From the results, the velocities obtained at all permanent stations by processing the time series
of GPS observations are changing yearly while the velocity model gives constant velocity for each
station yearly. Nevertheless, the velocity vector length which obtained by the local velocity model
is closest to the velocity vector length which obtained by GPS processing when increasing the time
difference between the GPS sessions , this is appear in HARN station (0Z17) where the difference in
velocity vector length is 0.5 mm at 17.14 years. Finally we created a computer program to compute
the HARN stations at any epoch on ITRF08 by using the local velocity model and the transformation
parameters between ITRF94 and ITRF08.
Recently, several high and ultra-high degree global harmonic models have been developed. They are
typically used in local gravity field modeling via the remove- restore technique, in order to
establish accurate and precise local geoid solutions. In the current study, a comparison is
performed, concerning Egypt, among the behaviors of the new harmonic models EGM96, GFZ97 and GPM98C
with respect to the available local data. These comparisons ascertain that none of these new models
recover the long-medium spectral information in a reliable manner, due to the absence of the
Egyptian local data during the global solutions for those harmonic models. Among the three
investigated harmonic models, the EGM96 model, as a reference field, seems to perform slightly
better than the other two models, based on the available Egyptian data set. So, it is recommended
to improve the EGM96 model, using the local Egyptian data.
New additional Global Geopotential Models [GGMs] have now been released into the public domain,
those including data from the CHAMP, GREACE and GOCE dedicated satellite gravimetric mission. Those
satellite tracking data have resolved the long wave length component of the global gravity field
with rather very high accuracy [10].
----------------------------------------------------------------------------------------------------
-----
2013, Civil Engineering Research Magazine CERM, Vol. 35 .No. (3), Published by Faculty of
Engineering, Al-Azhar University, Cairo, Egypt.
Therefore, it is important to evaluate those new models over Egypt to determine which; of them is
the most appropriate GGM there. In this study a comparison of the performance of three of the GGMs
released between 1996 tell now (EGM96, EGM2008 and EIGEN-6C 2011) over Egypt is made. The gravity
anomalies computed from the models are compared with point free air gravity anomalies on land. The
results have indicated the outstanding performance of EGM2008 to the other examined GGMs
undoubtedly. EGM2008 has1.23 times better statistics than the EGM96 and 2.54 times than EIGEN-6C
2011, in terms of root mean square error [r.m.s.e].
In the current study, 5'x5' grid values of geoidal heights, for the whole terri-tory of Egypt were computed by collocation technique, based on all the old and the recent available heterogeneous geodetic data. The well-known remove-restore technique was used for the purpose of maximally smoothing the used data as a pre-request by the collocation method. This was done, for the first time in Egypt, by the aid of an appropriate high degree global harmonic model, tailored to the local terrestrial data. A digital terrain model for Egypt was also used for the same purpose. The final results have shown a rather good internal and external accu-racy of the predicted geoid of about 0.22 m and 0.63 m respectively.
The fixed stations of a geodetic network are continuously changing, due to the change of its
tectonic plate. When the instantaneous coordinates of the stations at any epoch are needed, the
velocity of the stations should be known. The velocity of any station is determined by two
techniques, firstly by using the time series of GPS observation and secondly by using the created
velocity model of plate which obtained from the plate Cartesian rotation vector. In this research,
using the available number of the permanent GPS stations made by the Egyptian National Research
Institute of Astronomy and Geophysics (ENRIAG) to obtain the two velocity models of Nubian-plate
ITRF2008 for year 2011 and 2013.
Using the High Accuracy Reference Network (HARN) stations after transforming them from ITRF94 epoch
1996.0 into ITRF08 epoch 1996.0 to check the two local models by determining the velocities at all
stations. The maximum difference in velocities between these models is found within ±0.2 cm.
Therefore we took the mean of the two local models to create the best fit local velocity model.
Additionally we used the HARN network and permanent GPS stations to assess the local velocity model
with the velocity model of Nubian-plate ITRF08 which created by the IGS stations, the maximum
difference between them is found within ±0.14cm.
From the results, the velocities obtained at all permanent stations by processing the time series
of GPS observations are changing yearly while the velocity model gives constant velocity for each
station yearly. Nevertheless, the velocity vector length which obtained by the local velocity model
is closest to the velocity vector length which obtained by GPS processing when increasing the time
difference between the GPS sessions , this is appear in HARN station (0Z17) where the difference in
velocity vector length is 0.5 mm at 17.14 years. Finally we created a computer program to compute
the HARN stations at any epoch on ITRF08 by using the local velocity model and the transformation
parameters between ITRF94 and ITRF08.
Recently, several high and ultra-high degree global harmonic models have been developed. They are
typically used in local gravity field modeling via the remove- restore technique, in order to
establish accurate and precise local geoid solutions. In the current study, a comparison is
performed, concerning Egypt, among the behaviors of the new harmonic models EGM96, GFZ97 and GPM98C
with respect to the available local data. These comparisons ascertain that none of these new models
recover the long-medium spectral information in a reliable manner, due to the absence of the
Egyptian local data during the global solutions for those harmonic models. Among the three
investigated harmonic models, the EGM96 model, as a reference field, seems to perform slightly
better than the other two models, based on the available Egyptian data set. So, it is recommended
to improve the EGM96 model, using the local Egyptian data.
New additional Global Geopotential Models [GGMs] have now been released into the public domain,
those including data from the CHAMP, GREACE and GOCE dedicated satellite gravimetric mission. Those
satellite tracking data have resolved the long wave length component of the global gravity field
with rather very high accuracy [10].
----------------------------------------------------------------------------------------------------
-----
2013, Civil Engineering Research Magazine CERM, Vol. 35 .No. (3), Published by Faculty of
Engineering, Al-Azhar University, Cairo, Egypt.
Therefore, it is important to evaluate those new models over Egypt to determine which; of them is
the most appropriate GGM there. In this study a comparison of the performance of three of the GGMs
released between 1996 tell now (EGM96, EGM2008 and EIGEN-6C 2011) over Egypt is made. The gravity
anomalies computed from the models are compared with point free air gravity anomalies on land. The
results have indicated the outstanding performance of EGM2008 to the other examined GGMs
undoubtedly. EGM2008 has1.23 times better statistics than the EGM96 and 2.54 times than EIGEN-6C
2011, in terms of root mean square error [r.m.s.e].
In the current study, 5'x5' grid values of geoidal heights, for the whole terri-tory of Egypt were computed by collocation technique, based on all the old and the recent available heterogeneous geodetic data. The well-known remove-restore technique was used for the purpose of maximally smoothing the used data as a pre-request by the collocation method. This was done, for the first time in Egypt, by the aid of an appropriate high degree global harmonic model, tailored to the local terrestrial data. A digital terrain model for Egypt was also used for the same purpose. The final results have shown a rather good internal and external accu-racy of the predicted geoid of about 0.22 m and 0.63 m respectively.
The satellite-only model GOCO05s (complete to degree and order 280) and ultra-high degree geopotential model EGM2008 (complete to degree and order 2190) have been tailored to the Egyptian 5′×5′ mean gravity anomalies in order to select the optimal model that can be used for the reference gravity field for the new geoid model. The results show that both EG1GOC5s and EGTM0818 tailored geopotential models give less and better residual gravity anomalies, where the EGTM0818 tailored model has been improved significantly by about 27% than the EGM2008 model similarly, the EG1GOC5s tailored model better than the GOCO05s model by about 17%.
Gravimetric and combined (gravity and astrogeodetic data) geoids solutions for Egypt have been computed using both tailored geopotential models in the remove-restore technique through Least-squares Collocation (LSC). The computed geoids are fitted to the GPS/levelling stations. The results show that no significant variance between the gravimetric and combined geoids solutions exists. In addition, both combined geoids solutions are given the same accuracy, where RMS ≈ ± 15 cm.
Finally, a comparison between GPS/levelling stations and both NGRAV-A and NGRAV-B gravimetric geoids computed by using both EG1GOC5s and EGTM0818 models, respectively, give nearly the same external accuracy, where the RMS of the differences ± 13 cm for NGRAV-A and ± 15 cm for NGRAV-B. Therefore, we recommend that both tailored geopotential models as reliable models for geoid heights over Egypt.