Abstract
Global navigation satellite systems (GNSS) can attain centimeter level positioning accuracy, which is conventionally provided by real-time precise point positioning (PPP) and real-time kinematic (RTK) techniques. Corrections from the data center or the reference stations are required in these techniques to reduce various GNSS errors. The time-relative positioning approach differs from the traditional PPP and RTK in the sense that it does not require external real-time corrections. It computes the differences in positions of a single receiver at different epochs using phase observations. As the code observations are not used in this approach, its performance is not affected by the noise and multipath of code observations. High reliability is another advantage of time-relative precise positioning because the ambiguity resolution is not needed in this approach. Since the data link is not required in the method, this approach has been widely used in remote areas where wireless data link is not available. The main limitation of time-relative positioning is that its accuracy degrades over time between epochs because of the temporal variation of various errors. The application of the approach is usually limited to be within a time interval of less than 20 min. The purpose of this study was to increase the time interval of time-relative positioning and to extend the use of this method to applications with a longer time requirement, especially in remote areas without wireless communication. In this paper, the main error sources of the time-relative method are first analyzed in detail, and then the approach to improve the accumulated time relative positioning method is proposed. The performance of the proposed method is assessed using both static and dynamic observations with a duration as long as several hours. The experiments presented in this paper show that, among the four scenarios tested (i.e., GPS, GPS/Galileo, GPS/Galileo/BeiDou, and GPS/Galileo/BeiDou/GLONASS), GPS/Galileo/BeiDou performed best and GPS/Galileo/BeiDou/GLONASS performed worst. The maximum positioning errors were mostly within 0.5 m in the horizontal direction, even after three hours with GPS/Galileo/BeiDou. It is expected that the method could be used for positioning and navigation for as long as several hours with decimeter level horizontal accuracy in remote areas without wireless communication.
Highlights
IntroductionGlobal navigation satellite system (GNSS) precise positions can be determined conventionally using real-time precise point positioning (PPP) and real-time kinematic (RTK)
As the time-relative positioning method is based on a single receiver, the preprocessing process should be the same as precise point positioning (PPP) in order to remove or reduce as many errors as possible such as carrier phase windup effect, solid earth tide, ocean tide loading, satellite antenna phase center offset, etc
Conclusions method surveying and study navigation applications remote precise areas, such as parts of the Theforpurpose this was to provide a in relative positioning
Summary
Global navigation satellite system (GNSS) precise positions can be determined conventionally using real-time precise point positioning (PPP) and real-time kinematic (RTK). Techniques [1,2,3,4,5,6] These techniques need external support from a data center or reference stations to reduce various GNSS errors. Unlike these techniques, time-relative positioning computes the difference in positions of a single receiver at two epochs, as shown in Figure 1 [7,8,9,10].
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