The Earth system generates different phenomena that are observable at the surface of the Earth su... more The Earth system generates different phenomena that are observable at the surface of the Earth such as mass deformations and displacements leading to plate tectonics, earthquakes, and volcanism. The dynamic processes associated with the interior, surface, and atmosphere of the Earth affect the three pillars of geodesy: shape of the Earth, its gravity field, and its rotation. Geodesy establishes a characteristic structure in order to define, monitor, and predict of the whole Earth system. The traditional and new instruments, observables, and techniques in geodesy are related to the gravity field. Therefore, the geodesy monitors the gravity field and its temporal variability in order to transform the geodetic observations made on the physical surface of the Earth into the geometrical surface in which positions are mathematically defined. In this paper, the main components of the gravity field modeling, (Free-air and Bouguer) gravity anomalies are calculated via recent global models (E...
Digital Terrain Model (DTM) is a digital numerical representation of the Earth's surface. DTM... more Digital Terrain Model (DTM) is a digital numerical representation of the Earth's surface. DTMs have been applied to a diverse field of tasks, such as urban planning, military, glacier mapping, disaster management. In the expression of the Earth' surface as a mathematical model, an infinite number of point measurements are needed. Because of the impossibility of this case, the points at regular intervals are measured to characterize the Earth's surface and DTM of the Earth is generated. Hitherto, the classical measurement techniques and photogrammetry method have widespread use in the construction of DTM. At present, RADAR, LiDAR, and stereo satellite images are also used for the construction of DTM. In recent years, especially because of its superiorities, Airborne Light Detection and Ranging (LiDAR) has an increased use in DTM applications. A 3D point cloud is created with LiDAR technology by obtaining numerous point data. However recently, by the development in image m...
A digital terrain model (DTM) is defined as the digital cartographic representation of the elevat... more A digital terrain model (DTM) is defined as the digital cartographic representation of the elevation of the earth's surface created from discrete elevation points. DTMs have been applied to a diverse field of tasks, such as forest management, urban planning, ice sheet mapping, flood control, road design, hydraulic simulation, visibility analysis of the terrain, and topographic change quantification. In parallel with the developments in data processing technologies; satellite remote sensing, airborne laser scanning, and radar interferometry become efficient sources for constructing high quality DTMs in a cost-effective manner. The accuracy of DTM is influenced by several factors such as, the accuracy, the density, and the spatial distribution of elevation points, the terrain surface characteristics, and the interpolation methods. In this study, direct comparisons are made between curvature and grid data reduction algorithms for airborne Light Detection and Ranging (LiDAR) derived...
The eastern Anatolia provides one of the best examples of an area of rapid deformation and intens... more The eastern Anatolia provides one of the best examples of an area of rapid deformation and intense contraction that is the consequence of an active continental collision between the Arabian and Eurasian plates leading to large and devastating earthquakes. The latest evidence of the active tectonism in the region is revealed by two remarkable seismic events; Van-Tabanli (Mw 7.2, October 23, 2011) and Van-Edremit (Mw 5.6, November 9, 2011) earthquakes. The study of the earthquake cycle and observation of geodetic and seismic deformation in this region is very important to hazard assessments. In this study, the inter-seismic, co-seismic, and post-seismic movements caused by the above-mentioned earthquakes were investigated using the time series of 2300 days of Global Navigation Satellite Systems (GNSS) observations of the local stations selected from the network of the Continuously Operating Reference Stations, Turkey (CORS-TR). For the inter-seismic period, approximately 1100 daily da...
Afyon Kocatepe University Journal of Sciences and Engineering, 2017
High-degree geopotential models of spherical harmonic coefficients are used for modelling the ext... more High-degree geopotential models of spherical harmonic coefficients are used for modelling the exterior gravity field of the Earth. These coefficients are derived from satellite tracking data, altimeter data, and terrestrial and airborne gravity data. Hundreds of thousands of coefficients and standard deviation values for these coefficients are estimated from millions of measurements. The geopotential model accuracy is affected by the amount, the distribution and the type of measurements. The satellite gravity field missions have provided accurate data forming geopotential models since 1960's. The geopotential models related to the satellite gravity field missions are experienced by interior validation (estimated error degree variances of fully-normalized coefficients) or outer validation (comparison of model based gravity anomalies and geoid heights with terrestrial measurements). In this paper, recent high-degree geopotential models are primarily explained and evaluated by GNSS/levelling data of a selected study area. The objective of this evaluation is to determine the high-degree geopotential model giving a better fit to the GNSS/levelling data over the study area for the contribution to the regional geoid determination studies in Turkey.
Bu çalışmada, Harita Mühendisliğinin en önemli uygulamalarından biri olan lokal jeoid tespiti içi... more Bu çalışmada, Harita Mühendisliğinin en önemli uygulamalarından biri olan lokal jeoid tespiti için kullanılan noktalar arasındaki mesafenin enterpole edilen jeoid yüksekliklerine olan etkisinin araştırılması amaçlanmıştır. Çalışma kapsamında, 36.5 0 40.5 0 enlem ve 26.5 0 33.0 0 boylam aralığındaki bölgede makro ve mikro ölçekte iki test ağı oluşturulmuştur. Makro ağda, 85 referans ve 35 enterpolasyon noktası olmak üzere toplam 120 nokta, mikro ağda, 8 referans ve 3 enterpolasyon noktası olmak üzere toplam 11 nokta kullanılmıştır. Elipsoidal yüksekliklerden ortometrik yüksekliklere dönüşüm için gerekli olan lokal jeoid modellerinin tespitinde Ters Mesafe ile Ağırlıklı (TMA), Kriging (KRG), En Küçük Eğrilik (EKE), Radyal Bazlı Fonksiyon (RBF) ve Geliştirilmiş Shepard (MSH) enterpolasyon yöntemleri kullanılmıştır. Hesaplanan Karesel Ortalama Hata değerleri karşılaştırılarak, çalışma bölgesindeki lokal jeoid tespiti için makro ağda GSH yönteminin ve mikro ağda EKE yönteminin en doğru sonucu verdiği belirlenmiştir.
The establishment of Turkish National Fundamental GPS Network (TNFGN) was completed in 2001 and L... more The establishment of Turkish National Fundamental GPS Network (TNFGN) was completed in 2001 and Large Scale Map and Map Information Production Regulation (LSMMIPR) came into force in 2005 in parallel with the establishment of TNFGN and the increase in the use of GPS applications. TNFGN has been designed as first order GPS network and it comprises second-, third-and fourth-order GPS densification networks. LSMMIPR has required determining the positions of first-, second-and third-order GPS densification (C1, C2 and C3) points with the reference epoch besides the measurement epoch. Therefore, it is necessary to estimate the velocity vectors of the densification points. In practise, the velocity vectors of C1, C2 and C3 points are estimated from TNFGN points or higher-order densification points velocity vectors by interpolation methods but LSMMIPR did not specify the interpolation method for this procedure. The objective of this study is to use a back propagation artificial neural network (BPANN) that has been more widely applied in engineering among all other neural network models for estimating the velocity of the densification point as an alternative to the interpolation methods. BPANN and selected ten interpolation methods are evaluated over a test area, in terms of root mean square error (RMSE). The results showed that the employment of BPANN estimated the densification point velocity (V X,Y,Z) with a better accuracy (±5.0 mm, ±4.0 mm, ±3.9 mm, respectively) than the interpolation methods in the test area and indicated that BPANN can be a useful tool for estimating point velocity in the densification networks as a real alternative to the interpolation methods.
There has been a need for geodetic network densification since the early days of traditional surv... more There has been a need for geodetic network densification since the early days of traditional surveying. In order to densify geodetic networks in a way that will produce the most effective reference frame improvements, the crustal velocity field must be modelled. Artificial Neural Networks (ANNs) are widely used as function approximators in diverse fields of geoinformatics including velocity field determination. Deciding the number of hidden neurons required for the implementation of an arbitrary function is one of the major problems of ANN that still deserves further exploration. Generally, the number of hidden neurons is decided on the basis of experience. This paper attempts to quantify the significance of pruning away hidden neurons in ANN architecture for velocity field determination. An initial back propagation artificial neural network (BPANN) with 30 hidden neurons is educated by training data and resultant BPANN is applied on test and validation data. The number of hidden ne...
The Earth system generates different phenomena that are observable at the surface of the Earth su... more The Earth system generates different phenomena that are observable at the surface of the Earth such as mass deformations and displacements leading to plate tectonics, earthquakes, and volcanism. The dynamic processes associated with the interior, surface, and atmosphere of the Earth affect the three pillars of geodesy: shape of the Earth, its gravity field, and its rotation. Geodesy establishes a characteristic structure in order to define, monitor, and predict of the whole Earth system. The traditional and new instruments, observables, and techniques in geodesy are related to the gravity field. Therefore, the geodesy monitors the gravity field and its temporal variability in order to transform the geodetic observations made on the physical surface of the Earth into the geometrical surface in which positions are mathematically defined. In this paper, the main components of the gravity field modeling, (Free-air and Bouguer) gravity anomalies are calculated via recent global models (E...
Digital Terrain Model (DTM) is a digital numerical representation of the Earth's surface. DTM... more Digital Terrain Model (DTM) is a digital numerical representation of the Earth's surface. DTMs have been applied to a diverse field of tasks, such as urban planning, military, glacier mapping, disaster management. In the expression of the Earth' surface as a mathematical model, an infinite number of point measurements are needed. Because of the impossibility of this case, the points at regular intervals are measured to characterize the Earth's surface and DTM of the Earth is generated. Hitherto, the classical measurement techniques and photogrammetry method have widespread use in the construction of DTM. At present, RADAR, LiDAR, and stereo satellite images are also used for the construction of DTM. In recent years, especially because of its superiorities, Airborne Light Detection and Ranging (LiDAR) has an increased use in DTM applications. A 3D point cloud is created with LiDAR technology by obtaining numerous point data. However recently, by the development in image m...
A digital terrain model (DTM) is defined as the digital cartographic representation of the elevat... more A digital terrain model (DTM) is defined as the digital cartographic representation of the elevation of the earth's surface created from discrete elevation points. DTMs have been applied to a diverse field of tasks, such as forest management, urban planning, ice sheet mapping, flood control, road design, hydraulic simulation, visibility analysis of the terrain, and topographic change quantification. In parallel with the developments in data processing technologies; satellite remote sensing, airborne laser scanning, and radar interferometry become efficient sources for constructing high quality DTMs in a cost-effective manner. The accuracy of DTM is influenced by several factors such as, the accuracy, the density, and the spatial distribution of elevation points, the terrain surface characteristics, and the interpolation methods. In this study, direct comparisons are made between curvature and grid data reduction algorithms for airborne Light Detection and Ranging (LiDAR) derived...
The eastern Anatolia provides one of the best examples of an area of rapid deformation and intens... more The eastern Anatolia provides one of the best examples of an area of rapid deformation and intense contraction that is the consequence of an active continental collision between the Arabian and Eurasian plates leading to large and devastating earthquakes. The latest evidence of the active tectonism in the region is revealed by two remarkable seismic events; Van-Tabanli (Mw 7.2, October 23, 2011) and Van-Edremit (Mw 5.6, November 9, 2011) earthquakes. The study of the earthquake cycle and observation of geodetic and seismic deformation in this region is very important to hazard assessments. In this study, the inter-seismic, co-seismic, and post-seismic movements caused by the above-mentioned earthquakes were investigated using the time series of 2300 days of Global Navigation Satellite Systems (GNSS) observations of the local stations selected from the network of the Continuously Operating Reference Stations, Turkey (CORS-TR). For the inter-seismic period, approximately 1100 daily da...
Afyon Kocatepe University Journal of Sciences and Engineering, 2017
High-degree geopotential models of spherical harmonic coefficients are used for modelling the ext... more High-degree geopotential models of spherical harmonic coefficients are used for modelling the exterior gravity field of the Earth. These coefficients are derived from satellite tracking data, altimeter data, and terrestrial and airborne gravity data. Hundreds of thousands of coefficients and standard deviation values for these coefficients are estimated from millions of measurements. The geopotential model accuracy is affected by the amount, the distribution and the type of measurements. The satellite gravity field missions have provided accurate data forming geopotential models since 1960's. The geopotential models related to the satellite gravity field missions are experienced by interior validation (estimated error degree variances of fully-normalized coefficients) or outer validation (comparison of model based gravity anomalies and geoid heights with terrestrial measurements). In this paper, recent high-degree geopotential models are primarily explained and evaluated by GNSS/levelling data of a selected study area. The objective of this evaluation is to determine the high-degree geopotential model giving a better fit to the GNSS/levelling data over the study area for the contribution to the regional geoid determination studies in Turkey.
Bu çalışmada, Harita Mühendisliğinin en önemli uygulamalarından biri olan lokal jeoid tespiti içi... more Bu çalışmada, Harita Mühendisliğinin en önemli uygulamalarından biri olan lokal jeoid tespiti için kullanılan noktalar arasındaki mesafenin enterpole edilen jeoid yüksekliklerine olan etkisinin araştırılması amaçlanmıştır. Çalışma kapsamında, 36.5 0 40.5 0 enlem ve 26.5 0 33.0 0 boylam aralığındaki bölgede makro ve mikro ölçekte iki test ağı oluşturulmuştur. Makro ağda, 85 referans ve 35 enterpolasyon noktası olmak üzere toplam 120 nokta, mikro ağda, 8 referans ve 3 enterpolasyon noktası olmak üzere toplam 11 nokta kullanılmıştır. Elipsoidal yüksekliklerden ortometrik yüksekliklere dönüşüm için gerekli olan lokal jeoid modellerinin tespitinde Ters Mesafe ile Ağırlıklı (TMA), Kriging (KRG), En Küçük Eğrilik (EKE), Radyal Bazlı Fonksiyon (RBF) ve Geliştirilmiş Shepard (MSH) enterpolasyon yöntemleri kullanılmıştır. Hesaplanan Karesel Ortalama Hata değerleri karşılaştırılarak, çalışma bölgesindeki lokal jeoid tespiti için makro ağda GSH yönteminin ve mikro ağda EKE yönteminin en doğru sonucu verdiği belirlenmiştir.
The establishment of Turkish National Fundamental GPS Network (TNFGN) was completed in 2001 and L... more The establishment of Turkish National Fundamental GPS Network (TNFGN) was completed in 2001 and Large Scale Map and Map Information Production Regulation (LSMMIPR) came into force in 2005 in parallel with the establishment of TNFGN and the increase in the use of GPS applications. TNFGN has been designed as first order GPS network and it comprises second-, third-and fourth-order GPS densification networks. LSMMIPR has required determining the positions of first-, second-and third-order GPS densification (C1, C2 and C3) points with the reference epoch besides the measurement epoch. Therefore, it is necessary to estimate the velocity vectors of the densification points. In practise, the velocity vectors of C1, C2 and C3 points are estimated from TNFGN points or higher-order densification points velocity vectors by interpolation methods but LSMMIPR did not specify the interpolation method for this procedure. The objective of this study is to use a back propagation artificial neural network (BPANN) that has been more widely applied in engineering among all other neural network models for estimating the velocity of the densification point as an alternative to the interpolation methods. BPANN and selected ten interpolation methods are evaluated over a test area, in terms of root mean square error (RMSE). The results showed that the employment of BPANN estimated the densification point velocity (V X,Y,Z) with a better accuracy (±5.0 mm, ±4.0 mm, ±3.9 mm, respectively) than the interpolation methods in the test area and indicated that BPANN can be a useful tool for estimating point velocity in the densification networks as a real alternative to the interpolation methods.
There has been a need for geodetic network densification since the early days of traditional surv... more There has been a need for geodetic network densification since the early days of traditional surveying. In order to densify geodetic networks in a way that will produce the most effective reference frame improvements, the crustal velocity field must be modelled. Artificial Neural Networks (ANNs) are widely used as function approximators in diverse fields of geoinformatics including velocity field determination. Deciding the number of hidden neurons required for the implementation of an arbitrary function is one of the major problems of ANN that still deserves further exploration. Generally, the number of hidden neurons is decided on the basis of experience. This paper attempts to quantify the significance of pruning away hidden neurons in ANN architecture for velocity field determination. An initial back propagation artificial neural network (BPANN) with 30 hidden neurons is educated by training data and resultant BPANN is applied on test and validation data. The number of hidden ne...
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