New Fast Precise Kinematic Surveying Method Using a Single Dual-Frequency GPS Receiver

摘要

As of this writing, there are two popular methods to perform precise surveying using the single dual-frequency Global Positioning System (GPS) receiver. One is the Real-Time Kinematic (RTK) technique. The other is the Precise Point Positioning (PPP) technique. The RTK technique requires GPS surveyors to have at least one GPS base station while the PPP technique needs a long observation period to resolve the carrier-phase ambiguities. This paper proposes a new, fast method that can conduct precise kinematic surveying using a single dual-frequency GPS receiver, overcoming the aforementioned problems. This new method, Absolute Plus Loop-based Accumulated-solution Time-relative (APLAT), combines the GPS absolute-positioning method and a loop-based accumulated-solution time-relative positioning method. In this APLAT method, the kinematic surveying trajectory must form a loop. The coordinates of the start-point of the loop can be precisely determined using the absolute positioning function of APLAT by making two short sessions of static observations. This function is useful if no control-point is available in the kinematic surveying. The relative positions of other kinematic surveying points in the loop are determined using the function of loop-based accumulated-solution time-relative GPS positioning. The integration of the absolute and the relative positioning functions allows kinematic surveying to precisely determine the absolute coordinates of each surveyed point in the loop. To determine the absolute coordinates of the start-point of a loop, only two short sessions (5 min each in this study) of static GPS observations (prior to starting and after completing the loop surveying) are required. The results of extensive absolute-positioning tests show that 3D-positioning standard deviation about 7 cm and root-mean-square (RMS) error about 13.4 cm can be achieved when the loop-duration is in the range of 40-80 min. Too short or long a loop-duration may degrade the absolute-positioning accuracy. Results from various relative positioning tests using the loop-based accumulated-solution time-relative method indicate that relative-positioning RMS errors of 1.3 cm, 2.6 cm, and 8.8 cm can be obtained for loop durations of 20 min, 40 min, and 60 min, respectively. This new APLAT method offers a new, fast, and precise (RMS error of 12 cm for absolute and RMS error of 8.8-cm relative positioning for 60-min loop duration) kinematic surveying method that is able to meet many GPS surveying and mapping requirements. This is particularly useful for postmission data processing in circumstances where single-base-station RTK or network RTK service is not available. In this study, the final precise-orbit and precise-satellite-clock data from the International GNSS Service are used to mitigate these errors. At present, this method is useful just for postmission applications, but it offers the flexibility of using absolute-positioning or relative-positioning function only, depending upon the specific surveying and mapping conditions and requirements. This method is a good complement to the PPP and RTK precise-positioning techniques currently in use. Due to the increasing spatial decorrelation of error sources, the positioning accuracy may degrade as the maximum spatial distance (approximately between the loop start-point and the loop middle-point) increases.