Ekrem Tusat - Academia.edu (original) (raw)

Papers by Ekrem Tusat

Bulletin of earthquake engineering, Jun 15, 2024

Research on the boron (B) toxicity problems had recently considerable relation, especially in the... more Research on the boron (B) toxicity problems had recently considerable relation, especially in the dry regions of the world. Development of resistant varieties to B toxicity is a high priority on these regions, where the soils have high levels of B. Thus, this study aimed to assessment the resistance of wheat genotypes to B toxicity using the agronomic and physiologic parameters. For this aim, a pot experiment, based on a completely randomized design with three replications, was conducted using the soil of calcareous usthochrepts. In the study, twenty different wheat genotypes of T. aestivum and T. Durum were used. Boron fertilizer at the levels of 0 (-B), 30 mg B kg-1 (+B) as H3BO3 was applied to the pots. After harvest, plant dry matter yield was recorded, and total B concentrations in tops of wheat plants were determined. The results have revealed the existence of a large genotypic variation among wheat genotypes to their physiologic and agronomic susceptibility to B toxicity.

Selcuk University Journal of Engineering, Science and Technology, Dec 31, 2018

Requirement for a high resolution geoid model has increased substantially during the last few dec... more Requirement for a high resolution geoid model has increased substantially during the last few decades especially with the advent of Global Positioning System (GPS). Many countries across the world have already developed their own geoidal model which serve as the means of deriving orthometric heights from GNSS observations. On the other hand, the need for transformation of the ellipsoidal heights derived from GNSS observations to the physical orthometric heights has forced geodesists to determine the high precision local geoid heights. Besides, because orthometric heights are used in engineering and GIS applications, local quasi-geoid determination studies have become especially important. As it is well known, Turkey is situated on a tectonically very active region and earthquakes occurring in different times cause deformations in heights of levelling points of Turkish National Vertical Network. On the other hand, National Mapping Agency of Turkey (GDM: General Directorate of Mapping) which is responsible for the establishment and maintenance of national geodetic networks compute geoid models for whole Turkey and release them for public use in different periods. These GDM-computed geoid models are called "hybrid geoid" models. Hybrid geoid models are computed with the combination of gravimetric geoid models and geoid heights on the GPS_levelling points. And it is also known that the absolute accuracies of these geoid models are nearly at the 10 cm level or even worse. But, the requested accuracy is about better than 5 cm. Hence, in order to prove that the required accuracy levels can be achieved, a local gravimetric and quasi-geoid determination project using the resources of Selçuk University was initiated. Project area has been planned to cover a limited part of Central Anatolia including Konya. Necessary basic data (gravity, levelling etc.) for this project have been obtained in the field by performing observations/measurements. Some other necessary data such as absolute gravity values have been obtained from GDM. And as the next phase, high accuracy (better than 5 cm) local gravimetric and quasi-geoid models will be computed for the limited part of Central Anatolia using the above mentioned data. In order to be able to reach this goal suitable geoid computations softwares must be used. In this project, we will use DFHRS developed by the Karlsruhe Applied Sciences and GRAVSOFT softwares. According to the results to be obtained from this project, a more comprehensive project will be launched and the project area will be expanded. Thus, additional gravity, levelling and GNSS measurements will be carried out in the new project area for the determination of a high accuracy regional gravimetric geoid.

Applied Soft Computing, Sep 1, 2021

Abstract Modeling and optimization from natural phenomena and observations of the physical earth ... more Abstract Modeling and optimization from natural phenomena and observations of the physical earth is an extremely important issue. In the light of the developments in computer and artificial intelligence technologies, the applications of learning-based modeling and optimization techniques in all kinds of study fields are increasing. In this research, the applicability of four different state-of-the-art metaheuristic algorithms which are Particle swarm optimization (PSO), Tree-Seed Algorithm (TSA), Artificial Bee Colony (ABC) algorithm, and Grey Wolf Optimizer (GWO), in local GNSS/leveling geoid studies have been examined. The most suitable geoid model has been tried to be obtained by using different reference points via the well-known machine learning algorithms, Artificial Neural Network (ANN) and Extreme Learning Machine (ELM), at the existing GNSS/leveling points in Burdur city of Turkey. In this study, eight different hybrid approaches are proposed by using each metaheuristic algorithm together with machine learning methods. By using these hybrid approaches, the model closest to the minimum number of reference points has been tried to be obtained. Furthermore, the performance of the hybrid approaches has been compared. According to the comparisons, the hybrid approach performed with GWO and ELM has achieved better results than other proposed hybrid approaches. As a result of the research, it has been seen that the most suitable local GNSS/Leveling geoid can be determined with a lower number of reference points in an appropriate distribution.

Geomatik, Aug 1, 2019

Global Konum Belirleme Sistemlerinin (GNSS) çok yüksek doğruluklar sağlamaya başlamasıyla birlikt... more Global Konum Belirleme Sistemlerinin (GNSS) çok yüksek doğruluklar sağlamaya başlamasıyla birlikte, uygulamada kısa sürede yüksek doğruluklu jeoit yüksekliklerinin elde edilmesi gereksinimi de önemli ölçüde artmıştır. Örneğin, mühendislik uygulamalarında ve CBS çalışmalarında ortometrik yükseklikler kullanıldığı için yerel jeoit belirleme çalışmaları daha da önem kazanmıştır. Bilindiği gibi Türkiye tektonik olarak aktif bir bölgede olup, farklı zamanlarda meydana gelen depremler ülke nivelman ağındaki noktaların düşey konumlarında deformasyonlara/değişimlere neden olmaktadır. Diğer taraftan Ülke Temel Jeodezik Ağlarının kurulması ve yaşatılmasından sorumlu olan Harita Genel Müdürlüğü (HGM; eski adıyla Harita Genel Komutanlığı), 1999 yılından bu yana GNSS ölçülerinden yararlanarak farklı yıllarda güncel Türkiye Jeoidi modelleri hesaplayarak, kullanıcıların hizmetine sunmaktadır. HGM tarafından bu güne kadar hesaplanmış olan jeoit modellerinin dış doğrulukların genel olarak 10 cm'den daha iyi olmadığı değerlendirilmektedir. Oysa kullanıcıların ihtiyacı olan bu doğrulukların 10 cm'den daha iyi olması arzu edilen bir durumdur. Söz konusu doğruluklara ulaşılıp ulaşılamayacağının araştırılması için Selçuk Üniversitesi olanakları ile pilot bir uygulama yapılması hedeflenmiş ve bu amaçla sadece İç Anadolu'nun belirli bir kesimini kapsayacak yerel gravimetrik jeoit ve geometrik yaklaşımla yaklaşık(quasi)-jeoit hesaplanması için Konya Selçuk Üniversitesi kaynakları kullanılarak bir bilimsel araştırma projesi başlatılmıştır. Söz konusu proje bölgesine ilişkin mevcut GNSS ve nivelman verilerine ilaveten gravite verileri arazide ölçülmüş ve mutlak gravite değerleri, TG-03 kestirim değerleri gibi bazı diğer veriler de HGM'den temin edilmiştir. Yerel quasi-jeoit hesabında Karlsruhe Üniversitesi Uygulamalı Bilimler Enstitüsü tarafından geliştirilmiş ve proje kapsamında temin edilmiş olan DFHRS (Sonlu Elemanlı Yükseklik Referans Sistemi) yazılımı kullanılmıştır. Söz konusu yazılım sürekli polinomsal yükseklik referans sistemi ve GNSS ile elde edilen elipsoidal yüksekliklere dayalı olarak jeoit yüksekliklerinin N(φ, λ, h) parametrik modellenmesi prensibine dayanmaktadır. Bu yazılım ile yapılan hesaplama sonucunda 10 cm'den daha iyi doğruluklu yerel quasi-jeoit elde edilmesi sağlanmıştır. Aynı noktalardaki GPS/Nivelman jeoidi, DFHRS hesap ve TG-03 kestirim değerleri birbirleriyle karşılaştırılmıştır. Netice olarak, bu makalede proje kapsamında sadece geometrik yaklaşımla hesaplanmış olan quasi-jeoit modeline ilişkin yapılmış olan çalışmalar ile ulaşılmış olan ara sonuçlar sunulmaktadır.

International Journal of Physical Sciences, Feb 18, 2011

Three-dimensional (horizontal, vertical and ellipsoidal heights) coordinates of a point can be ob... more Three-dimensional (horizontal, vertical and ellipsoidal heights) coordinates of a point can be obtained using the GNSS (global navigation satellite system) systems. Although, ellipsoid heights have a geometrical meaning, height is actually a geopotential value. Therefore, determination of physical reference surface (sea level or geoid) is of particular importance in geodetic studies. Although, GNSS observations provide ellipsoidal heights (h), in practice, orthometric height (H) is used. Since the relationship between these two heights is H=h-N, geoid undulations (N) that provide transition between ellipsoidal heights and orthometric heights need to be known. In this comparison of geoid height calculation methods, a network of 126 points was chosen within the borders Adiyaman in Southeastern Turkey. Reference geoid heights were determined according to the GNSS/levelling method across the entire network. The heights of these points were then remodelled according to both the adaptive neural fuzzy inference systems (ANFIS) and the polynomial coefficients methods. In the modelling procedure, 106 points were used to develop the two models and the remaining 20 points were used to test the results obtained from each model. The geoid heights obtained via both remodelling methods were compared with reference data from the GNSS/levelling method and the results of the comparison were interpreted.

Arabian Journal of Geosciences, Dec 1, 2018

Ellipsoidal heights are determined with high accuracy using Global Navigation Satellite System (G... more Ellipsoidal heights are determined with high accuracy using Global Navigation Satellite System (GNSS) techniques. In infrastructure projects undertaken for engineering purposes, orthometric heights are used. Geoid determination studies based on these two height systems are growing in importance. Although various methods are employed in geoid determination, one of the most commonly used in practice is local geoid determination. Points with known orthometric and ellipsoidal heights are used as reference points. These reference points are utilized to determine local geoid models for project area. The formation and selection of the most appropriate and true-to-reality model during modeling are a matter of extreme significance for practitioners who employ such models. In this study, we aim to establish a GNSS/leveling geoid in a test network that was formed in Konya for the purpose of local geoid determination. Validity tests are carried out for five different geoid models. These geoid models are determined using polynomial models of up to the third degree, and an exploration of the parameters that could be used in the decision-making process is performed. In accordance with the results of these calculations, the selection of an appropriate model among different potential polynomial models in local geoid modeling is explained in terms of theoretical references, an application is examined using the data from the study area, and the results are compared.

International journal of engineering and geosciences, Feb 1, 2018

There are mainly two different orbital information, namely broadcast ephemerides and IGS final ep... more There are mainly two different orbital information, namely broadcast ephemerides and IGS final ephemerides (IGS rapid, ultra rapid, predicted and final ephemerides) used in the GPS positioning. The broadcast ephemerides used in practice and real time are obtained through assessments derived from the observations from the USA GPS reference stations. Broadcast ephemerides are formed (depending on GPS week) from satellite information and the accuracies they provide are adequate in many GPS applications. On the other hand, several parameters (for example, information about gravity area, improved satellite orbit information, etc.) need to be known in order to attain high accuracy in engineering and geodetic applications. Final ephemeris information can be downloaded from the related web sites via the internet. In this study, Keplerian motion and Keplerian orbital parameters will be explained briefly and extensive information about ephemerides and numerical applications will be given. Within this scope, for GPS satellites, ECEF coordinates of the satellites were computed using the broadcast ephemerides. The coordinates computed by using broadcast ephemerides were compared with the coordinates obtained from the IGS final orbits.

Geomatik, Apr 15, 2018

Birçok mühendislik projesi, kuruluş ve ülkeler yeryüzündeki konumları nedeniyle veya çalışma amaç... more Birçok mühendislik projesi, kuruluş ve ülkeler yeryüzündeki konumları nedeniyle veya çalışma amaçlarına göre birbirlerinden farklı koordinat sistemleri kullanır. Günümüzde genellikle, daha önce yerel koordinat sistemleri ile belirlenmiş olan konum değerlerinin ve harita altlıklarının, global koordinat sistemleri üzerindeki karşılıklarına ihtiyaç duyulmaktadır. Bu durum datum dönüşümü yapmayı gerektirmektedir. Çeşitli koordinat sistemlerine ait verilerin diğer bir sistemdeki karşılığı bulunmak istendiğinde datum dönüşümü uygulanır. Datum dönüşümleri yapılırken benzerlik, afin ve projektif dönüşüm yöntemleri kullanılabilir. Her bir yöntem için ayrı işlem adımları uygulanır ve aynı işlem için sonuçlar farklı olabilir. Arazi koordinatlarının dönüşümünde benzerlik dönüşümü yaygın olarak kullanılırken, fotogrametri ile kartografya alanlarında afin ve projektif dönüşüm yöntemleri sıklıkla kullanılır. Bu çalışmada iki farklı koordinat sistemindeki karşılıkları bilinen noktalar ile arazi koordinatlarının iki boyutlu dönüşüm uygulamaları incelenmiştir. Hesaplamalar MS Excel ortamında yapılmış olup dayanak noktalarının konumları ile uygulanan yöntemler arasında karşılaştırmalar yapılmıştır. Uygulamalar sonucunda arazi koordinatlarının dönüşümünde projektif dönüşüm yönteminin uygun olabileceği belirlenmiştir.

Tehnicki Vjesnik-technical Gazette, Feb 1, 2018

The ongoing developments in Global Navigation Satellite Systems (GNSS) technology affect techniqu... more The ongoing developments in Global Navigation Satellite Systems (GNSS) technology affect techniques in geographic information and associated documents. The national Continuously Operating Reference Station (CORS) networks, which operate on the Real Time Kinematic (RTK) principle, are multipurpose geodetic networks and offer services to a large portion of society including all the public institutions and other organizations, military and civilian users and to scientific researchers. It is possible to utilize these networks both in real time positioning applications using the Network Real Time Kinematic (NRTK) method and in static applications using the Receiver Independent EXchange (RINEX) format data from reference stations. In this study, Virtual Reference Station (VRS) and static GNSS measurements were undertaken based on a Continuously Operating Reference Station-Turkey (CORS-TR) network in a test network established in Turkey. As a result of the measurements, repeatability attained using the VRS method was examined. Moreover, the coordinates obtained from VRS measurements based on CORS-TR network were compared with the coordinates calculated as a result of static observations. From the accuracies and repeatability, an investigation was implemented to determine the extent to which NRTK applications in real-time GNSS networks can be used to produce spatial data and create topographic maps.

Arabian Journal of Geosciences, Feb 1, 2021

Sinkholes (dolines) are considered natural hazards that threaten both human life and agricultural... more Sinkholes (dolines) are considered natural hazards that threaten both human life and agricultural economic income. Due to their characteristic sudden occurrences, sinkholes are almost impossible to avoid. Geology, hydrogeology, irrigation, precipitation, climate, land use changes, and urbanization are the main factors that activate sinkhole occurrences. More than 300 sinkholes have been reported in the Karapınar region situated in Konya Province, Turkey, and this number has increased in the last 5 years. In particular, increasing agricultural activities cause rapid lowering of groundwater levels by excessive pumping for irrigation. A total of 55,267 water wells are in use in the region, which increases the risk factors for sinkholes in Karapınar. The importance of Karapınar region for solar energy, intensive agricultural activities, and a planned thermal power plant to be built soon gives estimating sinkhole probability and investigating ways of predicting and preventing sinkholes vital importance. The main purpose of this study is to predict possible sinkhole formation in the Konya region based on historical occurrences and to ensure reporting to authorities to raise awareness of this problem. Sinkhole susceptibility maps using the AHP, TOPSIS, and VIKOR methods, which are included in the multicriteria decision analysis (MCDA) concept, were prepared for the Karapınar region to achieve this purpose. The elevation, slope, geology, rock strength values, land use, water well density, and distance to settlements and roads were considered criteria to generate the sinkhole susceptibility maps. Strength test results (geological data set), which were not added to susceptibility maps in previous studies, were used in this study. The generated susceptibility maps were verified by correlation analysis and by overlaying existing sinkholes with susceptibility values. Necessary suggestions are presented for the Karapınar region based on the results of this study. The calculated ratios using the AHP, TOPSIS, and VIKOR methods are 3.53%, 2.55%, and 2.86%, respectively, which imply that the study area is highly susceptible to sinkhole occurrences. Based on the correlation analysis, an r value of 0.982 is derived using the AHP and VIKOR methods. When existing sinkhole locations are considered, the AHP method produces the most likely sinkhole locations. In addition, the AHP method can be used to prepare and update the susceptibility maps for any region that is at risk of sinkhole formation.

Optical Engineering, Nov 21, 2014

Terrestrial laser scanning has been used for various outdoor visualizations such as urban, constr... more Terrestrial laser scanning has been used for various outdoor visualizations such as urban, construction, excavations, and land topography. Since laser scanning data have their own local coordinates in each station, a three-dimensional point cloud model of the object of interest is created in the local coordinate system by the combination of these measurements. For spatial queries and computations, the point cloud and other spatial data should be combined in a common coordinate system. In this study, a terrestrial laser scanner (TLS) and global navigation satellite system (GNSS) receiver were integrated for the registration of the laser scanner measurements into the geodetic coordinate system. Two georeferencing methods based on the continuously operating reference stations in the network Turkey (CORS-TR) were introduced. After the building was modelled by integrating the TLS and the GNSS receiver, the point cloud model that was created was registered to the international terrestrial reference frame. The registration was performed with 0.05 m root mean square error for the two georeferencing methods.

Geomatik, Dec 1, 2019

Öz GPS ile konum belirlemede, konum belirleme yöntemine ve hedeflenen doğruluğa bağlı olarak iki ... more Öz GPS ile konum belirlemede, konum belirleme yöntemine ve hedeflenen doğruluğa bağlı olarak iki farklı yörünge bilgisinden bahsedilebilir. Bunlar; yayın (broadcast) efemerisi ve hassas (precise) efemerisdir. Gerçek zamanlı konum belirlemede yayın efemerisi kullanılmakta olup yaklaşık 1-10 m doğruluğu elde etmek olanaklıdır. Ancak daha yüksek doğruluk beklenen uygulamalar ve özellikle ölçü sonrası büro hesaplamaları ile konum belirleme (statik GPS) için IGS hassas efemeris verileri tercih edilmektedir. Yayın efemeris bilgileri dünyaya dağılmış GPS Kontrol Bölümü izleme istasyonları tarafından yapılan gözlemler yardımıyla üretilmekte ve anlık olarak yayınlanmaktadır. Hassas efemeris verileri ise IGS yörünge bilgilerinden yararlanılarak 24 saat boyunca 30 saniye aralıklarla yapılan gözlemlerin değerlendirilmesiyle oluşmaktadır. Bunun sonucunda haftalık hassas efemerisler yayınlanmaktadır. Bir navigasyon mesajı şeklinde yayınlanan bu efemeris verileri herhangi bir zamanda uydunun anlık konumunun hesaplanabilmesini sağlayan bir Kepler elipsini ifade eder. Bu çalışmada ilk olarak 1 Ocak 2018 tarih 00:00 zamanına ait yayın efemerisi bilgisinden hesaplanan X, Y ve Z koordinatları ile aynı zamana ait IGS sonuç hassas efemeris verisi arasında karşılaştırma yapılarak yayın ve hassas efemeris verilerinin koordinatlar üzerindeki etkisi incelenmiştir. Daha sonra 31 Aralık 2017 tarih 22:00 zamanı ile 1 Ocak 2018 tarih 02:00 zamanı arasında 15 dakika aralıklarla X, Y ve Z koordinatları hesaplanmış ve aynı şekilde hassas efemeris verileriyle farkları alınmıştır. Bu uygulamada seçilen zamanın değiştirilmesiyle elde edilen yayın efemerisi ve hassas efemeris verileri aralarındaki farklar incelenmiştir.

International journal of environment and geoinformatics, Mar 1, 2017

The usability and the accuracy of internet-based position determination services which have gaine... more The usability and the accuracy of internet-based position determination services which have gained importance in recent years is one of the up-to-date subjects of studies. Online processing services have more advantages than commercial and scientific software; since they are easy to use, require less experience and free because they get quick results. In this study, GPS observation files in rinex format belonging to 6 stations were evaluated using Auspos, Magic-GNSS and Opus services then the results were obtained. Three systems showed the similar results for the results obtained according to 24-hour measurement period. In the second study, observation files were divided into 12, 6 and 2 hour groups and after the results were obtained they were compared to 24-hour results. According to the reports, it was seen that the accuracy decreased as the observation period got shorter. In all three systems, 24 and 12-hour observation accuracy occurs in cm measures. In 6 and 2 hour periods where the observation period is shorter, accuracy value reaches to 3-4 cm. According to these results, it is seen that although it generally depends on observation period, internet-based position determination services sustain adequate accuracy for basic geodetic network application that the topographical engineering needs.

E3S Web of Conferences, 2020

This study focuses on the potential transforming sunflower husk wastes into innovative green prod... more This study focuses on the potential transforming sunflower husk wastes into innovative green products to be used for the recultivation of contaminated soils. This transformation makes it possible to utilize the large quantity plant breeding by-products to obtain a highly porous biosorbent. Optimal conditions for the preparation of bisorbents can be determined based on measurements of their specific surface and porosity. It is shown that structural characteristics of sorbent depend on conditions of the pyrolysis of primary raw material. Optimal conditions for obtaining biosorbent with a specified proportion of mesoand micropores and high specific surface are performed under three-stage pyrolysis as given by following conditions: sample holding time of 10-30 min, final temperature 700°С, and heating rate 15°С/min. A 3-month incubation study was conducted to investigate its performance in stabilization of copper contamination in Fluvisol. The sequential extraction procedure showed that...

Fen ve mühendislik bilimleri dergisi, Apr 1, 2018

Dünya üzerindeki bütün ülkeler kendi konumsal bilgilerini sayısal ortamda saklamak ve kullanabilm... more Dünya üzerindeki bütün ülkeler kendi konumsal bilgilerini sayısal ortamda saklamak ve kullanabilmek için bir datum belirlemiştir. Bu datumu kullanarak ülkelerine ait jeodezik verileri bir altlık üzerine işleyerek her türlü planlama işlerinde kullanmaya başlamıştır. Fakat Küresel Uydu Konumlama Sistemi (GNSS) dünyada yaygınlaşması ile Konumsal bilgiler Uluslararası Yersel Referans Sistemi 1996 (ITRF96) datumunda elde edilmeye başlamıştır. Ülkeler için bu datumdan kendi ulusal datumlarına geçmek bir mecburiyet haline gelmiştir. Türkiye'de de Avrupa Datumu 1950 (ED50) kullanılmıştır. GPS alıcılarıyla elde edilen ITRF96 datumunda elde edilen koordinatların ED50 datumuna dönüştürülmesi gerekmektedir. 3D datum dönüşümü için bilim adamları tarafından birçok matematiksel yöntem geliştirilmiştir. Bu çalışmada bu yöntemlerden olan Helmert, Moledensky-Bedakas, Veis ve Afin yöntemleri aynı veri kümesinde test edilerek sonuçları karşılaştırılmıştır.

... M. ve YILDIZ F.: Global Konum Belirleme Sistemi Teori-Uygulama, Nobel Yayın Dağıtım, ISBN 975... more ... M. ve YILDIZ F.: Global Konum Belirleme Sistemi Teori-Uygulama, Nobel Yayın Dağıtım, ISBN 975-591-203-7, Ankara, 2001 KAHVECİ M.: Türkiye ... FIRAT O., ŞENGÜN YS, CİNGÖZ A.,GÜRDAL MA, KURT A.İ., OCAK M., TÜRKEZER A., YILDIZ H., BAYAZIT N., ATA M., ÇAĞLAR ...

Selçuk Üniversitesi Mühendislik, Bilim Ve Teknoloji Dergisi, Mar 1, 2004

ÖZET: GPS Sisteminde, yayın efemerisi ve hassas efemeris olmak üzere, iki tür yörünge bilgisi kul... more ÖZET: GPS Sisteminde, yayın efemerisi ve hassas efemeris olmak üzere, iki tür yörünge bilgisi kullanılmaktadır. Yayın efemerisi, anlık konum belirleme uygulamalarında, GPS navigasyon mesajının bir parçası olarak yayınlanmakta olup pek çok uygulama için duyarlığı yeterli olmaktadır. Bunun yanında yüksek duyarlık gerektiren uygulamalarda, GPS verilerinin gözlem sonrası büroda değerlendirilmesi aşamasında hassas yörünge bilgisinin kullanılması tercih edilmektedir. Bu çalışmada Konya Metropolitan sahası ve civarındaki 7 adet nokta ve uzunlukları 7~90 km arasında değişen 12 adet bazdan oluşan bir test ağında efemeris bilgisinin koordinatlara ve baz bileşenlerine etkisi araştırılmıştır. Bu amaçla efemeris bilgisi olarak hem gözlem esnasında kayıt edilen yayın efemerisi hem de IGS tarafından SP3 formatında internet üzerinden yayınlanan hassas efemeris bilgilerine göre değerlendirme yapılmıştır. Her iki yöntemle de elde edilen sonuçlar arasındaki farklar karşılaştırılarak, efemeris bilgisinin göreli konumlamaya etkisi yorumlanmıştır.

Selcuk University Journal of Engineering, Science and Technology, 2004