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The height obtained through the GNSS method is the ellipsoidal height and to have an efficient application in surveying it has to be converted into orthometric height. This paper aims to determine a local geoid model for a part of Duhok region based on the known orthometric height using GPS/levelling and assessing the precision performance of the t...
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... GNSS leverages the benefits of all global navigation systems, providing more access and availability of signals to operators. Multiple GNSS constellations improve the availability of the navigation solution, saving time and money by delivering increased location accuracy at enhanced performance while determining highly accurate elevations using GNSS is still a challenging task facing engineers nowadays (Abdulrahman, 2021). ...
This article explores the application of the Inverse Distance Weighting (IDW) interpolation method in determining normal heights, utilizing a network of points with measured ellipsoidal and normal heights by the use of GNSS/levelling method. The IDW method, which assumes that points closer to each other are more alike, is employed to locate points within the correct quadrant and calculate their normal height based on the determined average height anomaly across the entire area. The accuracy of this method is validated using check points. The article further discusses the methodology of normal height determination at a country level by using generated coefficients, representing the average difference between various height-systems, which could be used as an integral to the interpolation methods used for generating a refined Digital Elevation Model (DEM) across the country. This study contributes to the ongoing discourse on the effective use of interpolation methods in geospatial analysis and DEM generation. It provides valuable insights into the practical application of the IDW method and its potential for enhancing the accuracy of normal height determination and DEM refinement. Importantly, such methods hold significant value for countries lacking gravimetric data, as they provide a viable means of determining normal heights in the absence of a local quasi geoid model.
... In the field of geodetic surveying, the GPS is a highly developed technique. The GPS method is significantly more effective than more similar methods, including total station, level, and theodolite, in terms of the number of users, effective cost, inter-visibility, and accuracy [17][18][19][20]. Authors in [21] proved that produced DEM using DGPS data are more effective than DEM produced using contour separation or SRTM data. ...
... Some of these methods include linear interpolation, kriging, triangulation, natural neighbor, Inverse Distance Weighting (IDW), and polynomial regression [24,25]. In [17], various surface modeling techniques were employed, including nearest neighbor, natural neighbor, and IDW. ...
The main objective of this study is to describe the preparation of topographic maps using the Surfer software. A total of 159 regularly distributed Ground Control Points (GCPs) were collected with the use of the Differential Global Positioning System (DGPS). Seven methods (Contour Map, Post Map, 3D Surface Map, 3D Wireframe Maps, Grid Vector-1 Map, Color Relief Map, and Shaded Relief Maps) at the Surfer environment were used to prepare the topographic maps at the Mukhtar Village near the Al-Fallujah City. Contour lines with other features were superimposed on the DEM layer, which refers to the topography of the terrain inside this study area. The accuracy of the database's results was estimated, essential maps were given, and the results were efficient and effective. The most appropriate method to represent topographic maps was proposed, each of these techniques has been enough to provide us with a general understanding of the subject area.
... This surface extends through the continents and to all points on the geoid having the same gravity potential energy, and it is used as the reference surface for orthometric height measurement (Tata and Matthew, 2018). Farsat (2021) opined that heights obtained from GPS are typically heights above an ellipsoidal model of the Earth and are not consistent with levelled heights above mean sea level (MSL). Height determination has an increased importance in most of the practical applications of geodetic networks. ...
The use of orthometric height in geodetic applications provides elevations on the physical topographic surface of the earth rather than ellipsoidal heights that are not in conformity with the physical topography. Global positioning system (GPS)/levelling produces ellipsoidal heights that are not consistent with levelled heights above mean sea level. The study provides a practical solution of using the GPS levelling approach or the geoidal heights aimed at providing local orthometric height. Many research studies were conducted with a view of finding a viable solution to the derived orthometric heights. It was revealed that the research studies conducted were found lacking in the use of only lower order numerical solutions models, which limit the accuracy derived from the model, the use of online post-processing, RTKlib, and other non-precise software to obtain the coordinates of the stations used in the derivation of orthometric. Finally, the use of gravimetric data, with its temporal variation problem, poses a threat to the derivation of orthometric height, so also to the accuracy of the developed model. Considering factors while developing models for orthometric heights improves the accuracy in achieving required heights for geodetic applications and aids in fast-tracking mapping.
... Abdulrahman investigated geoid models based on orthometric heights using Global Positioning System (GPS)/leveling [7]. Two gravity models of the Earth of the Duhok region, Iraq, were obtained. ...
The purpose of this paper is to determine a high-precision the Republic of Albania geoid model in order to convert the ellipsoidal heights into orthometric heights. The Digital Finite-Element Height Reference Surface method was used to solve this problem. The following models were chosen as the Republic of Albania global geopotential models: EGM96, EGG97 and EGM2008. Calculations of mentioned models were performed for 151 points of the Republic of Albania territory using the Digital Finite-Element Height Reference Surface method to determine the height reference surface. The minimum, maximum, mean values, standard deviation and mean quadratic error of the models in question were identified. The results showed that EGM96 had a standard deviation of 8 cm, EGG97 had a standard deviation of 4.8 cm and EGM2008 had a standard deviation of 4.2 cm as the best model. Thus, it was proved that EGM2008 has topographic distribution and fits well in the extension of the territory of the Republic of Albania.
... Abdulrahman investigated geoid models based on orthometric heights using Global Positioning System (GPS)/leveling [7]. Two gravity models of the Earth of the Duhok region, Iraq, were obtained. ...
... The Mean Error (ME), the Root Mean Square Error (RMSE), and the Standard Deviation (SD) are examples of these indicators (Peprah et al., 2017). The Root Mean Square Error (RMSE) is used to check the accuracy of the variations between a computed or measured value and an estimated value (Abdulrahman, 2021). ...
The heights determined by Global Positioning System (GPS) refer to the ellipsoid called the World Geodetic System 1984 (WGS84). Global Geopotential Models (GGMs) that are available on GNSS commercial software are generally used to transform ellipsoidal heights to orthometric heights. In this study, the geoid heights of GPS/Levelling were computed to evaluate the accuracy of the geoid heights obtained from two GGMs, namely, the Earth Gravitational Model 96 (EGM96) and the Earth Gravitational Model 08 (EGM08). Seventeen (17) GPS/Levelling stations of the High Accuracy Reference Network (HARN) over Egypt were used for this purpose. The standard deviations for the differences between the geoid heights obtained through GPS/Levelling and those obtained from EGM96 and EGM08 were determined as ± 1.212 m and ± 0.543 m, respectively. This research confirms that the geoid heights obtained from EGM08 are closer to the geoid heights determined using GPS/Levelling over Egypt.
... The Global Navigation Satellite System (GNSS) is one of the positioning methods that has significantly developed in the last decades. Compared with other terrestrial positioning methods, e.g., positioning using a total station, GNSS is much more efficient, costeffective, and accurate [1]. One can achieve up to a few millimeters of positioning accuracy when using GNSS precise positioning techniques, such as static differential positioning and precise point positioning [2e5]. ...
The Global Navigation Satellite System (GNSS) positioning method has been significantly developed in geodetic surveying. However, the height obtained through GNSS observations is given in a geodetic height system that needs to be converted to orthometric height for engineering applications. Information on geoid height, which can be calculated using the global geopotential mode, is required to convert such GNSS observations into orthometric height. However, its accuracy is still insufficient for most engineering purposes. Therefore, a reliable geoid model is essential, especially in areas growing fast, e.g., the central part of Java, Indonesia. In this study, we modeled the local geoid model in the central part of Java, Indonesia, using terrestrial-based gravity observations. The Stokes' formula with the second Helmert's condensation method under the Remove-Compute-Restore approach was implemented to model the geoid. The comparison between our best-performing geoid model and GNSS/leveling observations showed that the standard deviation of the geoid height differences was estimated to be 4.4 cm. This geoid result outperformed the commonly adopted global model of EGM2008 with the estimated standard deviation of geoid height differences of 10.7 cm.
... For example, Erol and Çelik (2004b) achieved an accuracy of about 0.03 m using UK as an interpolation method, and 1 GHP/3 km. Abdulrahman (2021) achieved an accuracy of about 0.243 m using OK and 1 GHP/0.350 km, but in this case measurements are carried out by means Total Station (Trigonometric Levelling). ...
Local geoid models presenting higher resolution than global ones are generally derived by a combination of different datasets, integrating individual pure astrogeodetic, gravimetric and GNSS/levelling solutions. To define local geoid, different interpolators may be applied starting from dataset of geoid height values. It is well known that the accuracy of the resulting models depends not only by interpolation method, but also by points numerosity and distribution. This article aims to analyse the performance of Kriging approaches in dependence of the density of the dataset. The experiments are carried out on geoid heights extracted in random way from an already existing local geoid model: different subsets are organized containing an increasing number of points in the same area and each of them is submitted to Kriging interpolations (Universal Kriging and Ordinary Kriging). The resulting models are compared with the original one and residuals are calculated to evaluate the accuracy in dependence of point density. The results demonstrate the efficiency of the Kriging methods, highlighting the possibility to achieve higher accuracy (a few centimetres) using a point density of 1 point/100 sqkm, in absence of gravity anomalies. Ordinary Kriging provides better results than Universal Kriging but the undulations between the resulting models are minimal (a few millimetres) when a high number of points is involved. Furthermore, the results highlight the limit of the leave one out Cross validation since it supplies higher residuals than direct comparison for both Universal Kriging and Ordinary Kriging, when few points are used.
... Secondly, they have been considered the main gathering space for university users before buildings entries. Finally, UOS4 is highly visually appeared from different spaces and has easy access to the parking areas and car traffic while UOS5 is the main transitional space for gathering students between college buildings [34][35][36][37][38][39][40]. ...
In the last decade, there has been a swift rise in the number of universities all around Egypt. Universities play an important role in the cultural, economic, and social aspects of each city. Design of University Open Spaces (UOS) is critical and needs post-occupation studies. The study analyses of UOS were accomplished through multidimensional analysis of selected juxtaposed UOS at Seberbay Engineering College as part of Tanta University. The hybrid method of this study is derived from integrating space syntax methodology as a computational method and as an observational method. Not all University Open Places at Tanta University are now successfully used as primary social spaces. In some cases, the ratio of parking lots to car access routes needs to be balanced. Retrofitting designs of the two selected UOS may be used as study method examples for additional research.
... Therefore, long and medium local geoid disturbances lead to a significant change from the global geoid model to the local geoid model. Therefore, any local geoid model must consider the local gravity model (Abdulrahman 2020). Besides the geodetic importance of the local geoid computation as an essential vertical datum, it would also shade more light onto the lithospheric thickness of the study area. ...
The local hybrid geoid model for the western desert in Egypt is computed by recent data, including the global geopotential models, gravimetric measurements, and a high-resolution digital topographic model. The research points out the importance of accurate local geoid computation not only as a survey datum but also to figure out the crustal structure. Detailed crustal structure patterns could reveal the origin of artesian aquifers and geothermal activities of the selected region. In this research, recent global geopotential models deduced from recent satellite missions have been used. The oases’ area of the western desert in Egypt is characterized by an irregular topographic pattern suggesting a complicated geoid model. Six recent global geopotential models (GGMs) have been evaluated for long and medium wavelengths. GGM accuracy for each model has been computed using GPS leveling data. EIGEN-6C model with spherical harmonic expansion to degree 250 gives the smallest error with a standard deviation equal to 0.019mGal. Also, a high-resolution digital topographic model with 3arcsec is used for terrain correction (Tc). The resulting geoid has been evaluated using GPS leveling in the selected region. Due to the recent geopotential models with high accuracy, the random distribution and low terrestrial gravity data have not become a problem in calculating the local geoid model.
