Comparision of static GNSS, NETWORK-RTK, PPP, PPP-RTK and SBAS methods and their coordinate accuracy obtained from them

There are many methods used in determining position with satellites (GNSS: Global Navigation Satellite Systems). These can be summarized as static relative positioning, single point positioning (SPP), single point precise positioning (PPP), differential GPS/GNSS (DGPS/DGNSS), SBAS (Satelite Based Augmentation Systems), Static GNSS, standard RTK (Real Time Kinematic) and Network-RTK (CORS: Continuously Operating Reference Stations) solutions. The accuracies obtained using these methods depend on different data structures, receiver models, data collection frequency, mathematical modeling, etc., and the purpose (geodetic, geodynamic, cadastral, meteorology, real-time navigation, etc.) and users of each solution method may be different. Static GNSS measurement method is the best option when high accuracy is required, when long bases are in question, when atmospheric effects are taken into account, when satellite geometry does not allow other measurement methods, when systematic effects are taken into account (ionosphere, troposphere). With Network-RTK (CORS), it is generally possible to obtain map and position information with centimeter accuracy at the measurement point in a few minutes or even seconds. With PPP-RTK, in measurement studies where Network-RTK access is not available, where there is no long-term static measurement opportunity, and in cases where there is no internet/GSM access, it is possible to reach position and height accuracy in the cm-dm range after a convergence period ranging from a few minutes to a few 10 minutes depending on the service used via GEO satellites. SBAS (WAAS, EGNOS and MSAS etc.) is used as a quality control and monitoring system in the aviation sector. The correction information (orbit, clock and atmospheric) that increases the accuracy and reliability of the positions calculated in GPS receivers is sent to users via Geostationary (GEO) satellites. The idea here is to ensure that satellite navigation systems are accessible everywhere and at all times, accurate, reliable and easy to use, and to ensure that aircraft fly safely and ships navigate safely, especially in narrow straits and channels. SBAS, Network-RTK, PPP, PPP-RTK and Static Measurements offer different advantages and weaknesses for geodetic measurements. Which method is preferred depends on the user's needs, application area and accuracy requirements. In this thesis study, 10 Turkish National Fundamental GNSS Network (TUTGA) points located in the Ankara province region were selected as the study area. 3-hour observations were conducted at each point for static and PPP methods. For the PPP-RTK method, measurements were performed until a solution was obtained where the phase uncertainties were resolved (fixed) and these periods were recorded to determine the convergence time of each point. For the Network-RTK method, 60 epochs (1 measurement per second) were measured by connecting to the General Directorate of Land Registry and Cadastre (TKGM) servers. For the SBAS method, the positional accuracy of SBAS was evaluated by evaluating the ISTA IGS station with GPS and GPS+SBAS data. The coordinate and velocity values of the TUTGA points were obtained from the General Directorate of Mapping (HGM) and were accepted as known coordinates in order to determine the position accuracies of the applied methods. As a result of the field study, the coordinates obtained with the Static, PPP, PPP-RTK and Network RTK (CORS) methods were compared with the coordinates obtained from HGM, accepted as known, and the coordinate differences and Root Mean Square Error (RMS) values were calculated. In addition, the data of the ISTA IGS station was used to evaluate the SBAS method. As a result of comparing the precise coordinates obtained from HGM and the coordinates obtained as a result of the field study, RMS values of 2.5, 2.3, 2.8 cm were calculated for X, Y, Z positions with the static method. RMS values of 3.3, 3.0, 3.9 cm were calculated for X, Y, Z positions with the PPP method. RMS values of 6.8, 3.2, 25.0 cm were calculated for X, Y, Z positions with the PPP-RTK method and the convergence times for which the phase ambiguities were resolved (fixed) were recorded for each point and an average convergence time of 3.9 minutes was calculated. RMS values of 5.9, 3.4, 3.8 cm were calculated for X, Y, Z coordinate components with the Network-RTK (CORS) method, respectively. In order to calculate the position improvement of SBAS data, first SPP solution was made with GPS data, then GPS and SBAS data were solved together and it was calculated that SBAS improved GPS by 2.34 meters horizontally and 2.13 meters vertically.