EFFECT OF DIFFERENT NETWORK GEOMETRY ON GNSS RESULTS

EFFECT OF DIFFERENT NETWORK GEOMETRY ON GNSS RESULTS Abstract Global Navigation Satellite System (GNSS) is mostly used to establish geodetic networks in surveying engineering. To establish a geodetic network, one should have an understanding of the various types of geodetic networks, their design, accuracy requirements, and essence. The main area where GNSS networks are needed include mapping, tracking crustal movements, planning large engineering projects, implementing cadastral works, designing urbanization activities, GIS, etc. In GNSS network, stations are generally located where they are needed, but the observation schema between stations are important. The main goal of this research was to select the best observation schema of GNSS networks according to the number of receivers and the redundancy of the observation. In this research, six points were established after reconnaissance the field of the project. After preparation the sessions according to the number of receivers, time, and distance between points observations were made by using static method. Data collections were made by using two and three receivers. From data collected in three days four types of geometric design of GNSS network were selected. The first was Hub method that is from one fixed point the new points (i.e. six points in this study) were observed. The second one was Star method that is one fixed point in the center of the new network and observed unknown points. The third was Loop method 1 (using two receivers) where all baselines (i.e. 21 baselines in this study) were observed from one known point and the last was Loop method 2 (using three receivers) from one fixed point. These methods had some advantage and disadvantage according to the type of the project that are selected. Due to no redundancy, no close loop, and no nontrivial line between adjacent points the first and second methods are not recommended for the establishment of the precise GNSS network in our study. Keywords: GNSS network design, Redundancy, Static method, Session. FARKLI A Ğ GEOMETRISININ GNSS SONUCLARINA ETKISI Ozet GNSS (Global Navigation Satellite System) arazi olcmelerinde jeodezik aglarin kurulmasinda sikca kullanilir. Bir jeodezik agi kurmak icin, agin turunu, tasarimini, dogruluk isteklerini bilmek gerekir. GNSS aginin ihtiyac oldugu alanlar; haritalama, yer kabugu hareketlerinin izlenmesi, genis capli muhendislik projelerinin planlanmasi, kadastral calismalarinin uygulanmasi ve CBS aktivitelerini icerir. GNSS aginda, noktalar nerede ihtiyac duyulursa orada tesis edilir. Fakat noktalar arasindaki gozlem semasi onemlidir. Bu calismanin ana amaci; fazla gozlem sayisi ve alici sayisi dusunulerek GNSS aginda en uygun olcu tasarimini belirlemektir. Bu kapsamda proje sahasinda 6 nokta tesis edilmistir. Oturumlar hazirlandiktan sonra, alici sayisi, noktalar arasi uzaklik ve zaman goz onunde bulundurularak statik olculer gerceklestirilmistir. 3 gunluk veri toplama surecinde GNSS aginin farkli 4 cesit ag tasarimi denenmistir. Veri toplama surecinde iki ve uc alici kullanilmistir. Birincisi bir sabit noktadan yeni noktalara olcu yapan Hub metodudur (yeni nokta sayisi 6 dir). Ikincisi agin merkezindeki bir noktayi sabit alip diger noktalari gozlemleyen Star yontemidir. Ucuncusu bilinen bir noktadan tum noktalarin gozlemlendigi iki alicili Loop yontemidir. Sonuncusu iki sabit noktali ve uc alicili Loop yontemidir. Secilen projelerin turune gore yontemlerin ustunlukleri ve zayifliklari bulunmaktadir. Sayisal sonuclara gore fazla olcu sayisindaki eksiklik ve kapali luplarin olmamasi nedeniyle birinci ve ikinci yontem, yuksek duyarlikli GNSS ag tasariminda tavsiye edilmez. Anahtar Kelimeler: GNSS ag tasarimi, fazla olcu, Statik yontem, Oturum