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The integration of survey-grade Global Navigation Satellite Systems (GNSS) with photogrammetric measurement studies conducted with an aircraft has the potential to meet the need for the use of grou...

The extraction of artificial and natural features using light detection and ranging (Lidar) data is a fundamental task in many fields of research for environmental science. In this study, the possi...

We know that position accuracies from relative and static Global Positioning System (GPS) measurements are degraded by a variety of physical, hardware and software effects. As a result, users often take special precautions to minimise these effects and, hopefully, improve their accuracies when planning and making measurements. In this study, the effects of the baseline length (BL) and observation duration (OD) on vertical and horizontal positioning errors for relative, static GPS measurements were experimentally evaluated. In making this evaluation, 5 min to 24 hours GPS data, collected over a 15 day period, from the Southern California Integrated GPS Network (SCIGN), were analyzed. The root mean square (RMS) of the differences between the true and measured vertical (up/ellipsoidal height) and horizontal (north and east/latitude and longitude) positions of the included stations were computed and then used to create empirical error equations dependent upon the BL and OD. Considerations for the numb...

The purpose of this study is the solution of the transformation problem between the GPS networks and old geodetic networks based on the national coordinate system alternatively by a 3-dimensional robust polynomial transformation (3D.R.P.T). This study focuses on and probes 3D similarity (3D.S.T), 3D polynomial transformation with least squares estimate as equal-weighted (L.S.3D.P.T), 3D polynomial transformation based on weight with the inverse of the distances of common points to the centre of gravity (W.L.S.3D.P.T) and robust estimate approaches that are re-weighted and are based on iterative solution. A detailed mathematical model and solution algorithm of the proposed model is given, and it has been applied in a test area covering the city borders of Istanbul for which its results were studied and compared to other three methods.

Most commonly used method for the determination of geoid is the evaluation of GPS (Global Positioning System) and levelling measurements together. Despite the fact that geometric levelling (GL) is in general easy and practicable, it is a measurement method that is hard and uneconomic to apply particularly in mountainous, hilly and rugged areas. This study aims the use of precise trigonometric levelling (PTL) method instead of GL for the determination of precise geoid heights. The method has been probed into in consideration of the accuracy, practicability, measurement and evaluation criteria, and has been compared with GL measurement results. In addition, geoid profiles that have been determined both (GPS_GL) and (GPS_PTL) measurements have been compared with TG-99A (Turkish Geoid-1999A) and IGNA (Istanbul GPS Network) geoid models to explore their consistency.