GPS ile elektronik uzaklık ölçülerin ölçeklerinin karşılaştırılması
The scale comparison between GPS and EDMs
Yazar: AHMET KARABURUN
Danışman: DOÇ. DR. ERSOY ARSLAN
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Jeodezi ve Fotogrametri Ana Bilim Dalı
Derece: Yüksek Lisans, 1998
Konu: Jeodezi ve Fotogrametri = Geodesy and Photogrammetry
Dizin: Elektronik uzaklık ölçme = Electronic distance measurement ; GPS = Global Positioning System ; Ölçekler = Scales ; Ölçüm yöntemleri = Measurement methods

Özet:
ÖZET Bu çalışmanın amacı GPS ile Elektronik Uzaklık Ölçerlerin (EUÖ) ölçeklerinin ve GPS ve presizyonlu nivelman ölçmeleri ile elde edilen yükseklik farklarının karşılaştırılmasıdır. Bu amaçla Çilingirköy kontrol bazında GPS ve presizyonlu nivelman ölçmeleri yapılmıştır. Çalışmanın birinci bölümünde, genel olarak GPS hakkında bilgi verilmiştir.İkinci bölümde, ana hatlarıyla GPS anlatılmış ve sistemini oluşturan bölümler açıklanmıştır. Üçüncü bölümde ise GPS ölçmelerinin neler olduğu, yörünge ve saatler ve GPS in doğruluğunun nasıl sınırlandırıldığı anlatılmıştır. Dördüncü bölümde, GPS ile rölatif ve mutlak konum belirleme yöntemleri ile ölçme yöntemlerinden bahsedilmiştir. Beşinci bölümde GPS ölçülerini değerlendirme teknikleri ve bu ölçülerin nasıl dengelendiği açıklanmıştır. Altıncı bölümde, GPS ölçmelerinde hata kaynakları ve bunların nasıl elimine edileceği anlatılmıştır. Yedinci bölümde, Çilingirköy kontrol bazında yapılan presizyonlu nivelman ölçme sonuçlan ile bulunan yükseklik farkları ve bu baz hattında Elektronik Uzaklık Ölçerler ile daha önceden yapılan kenar ölçmeleri En küçük Kareler Yöntemine göre dengelenmiş ve sonuçlan verilmiştir. Kontrol bazında yapılan GPS ölçmelerinde Ll, L2, L1+L2 fazlan ile baz çözümleri yapılmış ve bunlar dengelenerek baz üzerindeki noktalar arasındaki uzunluklar ve yükseklik farkları bulunmuştur. Noktalar arasında EUÖ ile GPS ölçmeleri ve değerlendirmeleri sonucu bulunan kenar uzunluk ve yükseklik farkları ve EUÖ ile GPS arasında hesaplanan ölçek, tablolar ve şekillerle gösterilmiştir. Ayrıca noktalar arasında GPS ve presizyonlu nivelman ölçmelerinden elde edilen yükseklik farkları arasındaki farklar da tablo ve şekillerle gösterilmiştir. XVI

Abstract:
SUMMARY THE SCALE COMPARISON BETWEEN GPS AND EDMs GPS has occupied a great place in the lives of surveying engineers because of its excellent accuracy, cheapness and high rate. It is also going on to develop with a great accelaration. Global Positioning System (GPS) comprises the observational and computational techniques which allow the geodetic problems by the use of precise measurements to, from or between artificial, mostly near earth satellites. The NAVSTAR GPS (NAVigation System with Time and Ranging Global Positioning System) is a satellite-based radio navigation system providing precise three-dimensional position, navigation, and time information to suitably equipped users. The system will be continuously available on a world wide basis, and is independent of meteorological conditions. GPS has been under development in the U.S.A. since 1973, and is primarily a military system, with limited acces to civilean users. It has been used for the solution of geodetic problems since about 1983. The system consists of 21 satellites (plus three active spares), placed in orbits of about 20,200 km altitude above the earth's surface. The final arrangemen of satellites is planned in such a way that at least four satellite are simultaneously visible above the horizon anywhere. GPS is primarily a navigation system. The fundamental navigation principle is based on the measurement of so-called pseudoranges between the user and four satellites. Starting from a known satellite coordinates in a suitable reference frame the coordinates of the user antenna can be determined. The description of the GPS system follows the division that is customary for navigaion satellites i.e.. Space segment. Control segment. User segment The space segment consists of active satellites. The satellites are placed in almost circular orbits in six orbital planes, with an orbital inclination of 55 XVUdegrees. Three types of satellites can be distinguished: - BlockI development satellites - Block II production satellites - Block II R replenishment satellites. The control segment consists of Main Control Station, Monitor Station and Ground Antenna. The tasks of the control segment are. monitor and control the satellite system continuously. determine the GPS system time. predict the satellite ephemerides and the behaviour of the clocks. update periodically the navigation message for each particular satellite. Appropriate satellite receivers are required to use the GPS signals for navigation purposes of for geodetic positioning. GPS is still in its development phase, and so too is receiver design. The main componenets of a GPS receiver are. antena with preamplifier. RF section with signal identification and signal processing. microprocessor for receiver control, data sampling, and data processing ( navigation solution). precision oscillator. power supply. user interface, command and display panel. memory, data storage All observations made simultaneously during a satellite coverage phase in the course of a GPS project are called a session. A session maybe as short as a few minutes,if fast ambiguity solution techniques are applicable in small networks, or it may cover several hours, as long as the satellite coverage allows, if highest accuracy is envisaged in larger networks. The following observation and evalution strategies are in use:. Single-station adjustment. Processing of single baseline and subsequent combination of baselines into networks. Processing of all simultaneously observed data of a single session in a joint adjustment (multi-station adjustment) f combination of several session solutions into rigorous everall network solution (multi-session adjustment) The particular error sources are assigned to three main groups. Satellite position errors. Signal propagation errors. Receiver errors The accuracy of GPS positioning depends on two factors:. The accuracy of a single pseudorange measurements, expressed by the User Equivalent Range Error (UERE) or by the associated standart deviation or. The geometric configuration of the satellites.The accuracy achievable with GPS for geodesy, surveying, and navigation, depends on several conditions, e.g.. Single or multi-receiver operation. Single or dual-frequency data. Receiver noise level. S A on or off. P-code available or not. Static or kinematic positioning. Real-time or post processing results. Extent of data modelling. Accuracy of orbits The applications of Global Positioning System Methods are determined by the achievable accuracy, the necessary effort and expense of equipment and computation and finally by the observation time. A very extensive catalogue of applications can be compiled given the current developments in precision methods with the real-time near real-time capabilities. The current interest in the use of satellite methods for practical tasks in geodesy becomes clearly visible. Since GPS is an all-weather, real-time, continuously available, economic, and very precise positioning technique, almost unlimited possibilities are opened up for its use in geodesy, surveying, navigation, and related fields, including: -Control surveying -Cadastral surveying -Geodynamics -Monitoring and engineering problems -Precision navigation -Marina and glacial geodesy. The aim of this study is scale factor comparison between GPS and EDMs. To achieve this aim all observations were carried out on the baseline in ÇİLİNGİRKÖY. Çilingirköy baseline consists of 8 pillars and has a distance of 5 km. Initially precise levelling was carried out between points on the baseline. The height differences between the points were calculated from precise levelling observations. Zeiss Ni 1(81449) precise level was used for the levelling procedure. Due to some unvisibility conditions the distances between the points on baseline were unobservable hence an the old observations made with high precision EDM MEKOMETER -5000 and HP 3808 A was used on this baseline for distance measurements. The distances were adjusted according to Least Squares Method and the horizontal distances were calculated. GPS observations on the baseline points were made according to the Static Method. All GPS observations of the baseline were completed within 1 day xixusing Leica System 300 dual frequency, with three GPS units receiving signals from the same satellite at the same time. One GPS receiver was always positioned on the reference point, and the other receivers at any of the other points. To succesfully capture the data, a sufficient observation period of approximately 25-30 minutes was maintained on the satellites. Finally, after the surveying, the adjusted coordinates of point were calculated, by processing GPS observations with Leica SKI / Data processing version 2.1 software. The introduction of the study has been explained in chapter 1 and and the fundementals of Global Positioning System have been explained chapter 2. The GPS Observables have been explained and the main characteristic and differences of the GPS observables have been summarized in chapter 3. The navigation with GPS has been explained in chapter 4. The GPS observing methods, setting up an observation plan and observation strategies and network desing have been mentioned in this chapter. Technigues of processing GPS observables and adjustment method have been explained in chapter 5. The error budget and corrections of GPS have been mentioned in chapter 6. Satellite, signal nad receiver errors have been explained in this chapter. In chapter 7 the application firstly precise levelling procedure have been mentioned and then the distances measured with EDMs have been adjusted according to the last squares method. Adjusted GPS observations have been compared with precise levelling observables and EDM observables. The differences between measurements have been shown with tables and figures. The scale coefficient of GPS and EDMs have been computed. The results of this study have been explained in chapter 8. The scale that was computed in this study between Leica System 300 and HP 3808 A with LI phase is 4 ppm and 2 ppm with L2 phase and 5 ppm with L+L2 phase and 5 ppm with L1+L2 phase using computed inospheric model and Hopfield tropospheric model. The scale that was computed between Leica System 300 and Mekometer-500 with LI is 3 ppm and 1 ppm with L2 phase and 3 ppm with L1+L2 phase and with L1+L2 phase using computed inospheric model and Hopfield troposheric model. The differences between the height differences of points computed from GPS and precise levelling observations showed the changes of the geoid in Çilingirköy. XX