Accuracy Assessment of GPS_RTK Grid to Ground Solutions
International Journal of Computer Science and Security (IJCSS), 6 (3):
23 - 32 (June 2019)Abstract
Global Navigation Satellite Systems (GNSS) become the main observation technique of the surveying work. Almost, it takes place the traditional methods because of its ability to do the surveying work economically, effectively and rapidly. The Real Time Kinematic (RTK) is a basic technique for topographic and engineering surveys. The common issue with RTK measurements in civil projects is the difference in the surfaces used for design and that used for measuring. While projects are designed on ground, the RTK measurements are done on flat (Grid) surface. This cause a problem for engineering drawings and project implementation. For compatibility between design and measurements, a conversion of distances from grid to ground or vise versa should be performed. In this paper, three approaches to solve the linear distortion problem are investigated. These approaches include applying scale factor, using control points and designing Low Distortion Projection (LDP) surface. To achieve the research goal, the coordinates of 13 check points were computed and adjusted after total station measurements of the traverse that connect these points with one control point. The traverse stretched for about 1400 m in the east west direction which affected by projection. The coordinates of the check points were obtained again through RTK_GPS measurements considering the control point as base station. The three solution approaches were utilized, and the results were analyzed. The Root Mean Square Error (RMSE) of relative position of points were 2.3, 2.8 and 3.2 cm when using control points, scale factor and LDP respectively. The RMSE of the absolute positions were 3.8, 13.3 and 13.4 cm.