Abstract
Global Satellite Navigation System (GNSS) can't provide normal location service in the indoor environment because the signal can be blocked by buildings. The pseudolites system can supplement GNSS, especially in the indoor environments. A new indoor array pseudolites system is introduced, its multi-channel transmitter has an identical clock source. The high-precision Doppler positioning method based on Z-fixed Known Point Initialization (Z-KPI) is developed without ambiguity resolution. Some static and dynamic tests are conducted to evaluate the positioning accuracy of this new method. In the static testing, the average Doppler measurement error is 1x10-5 m/s, which lays the foundation of the high precision velocity measurement, and the average positioning error is 0.02 m in X axis, 0.004 m in Y axis, and the average velocity error is 3.28x10 -5 m/s in X axis, 1.94x10 -5 m/s in Y axis. In the dynamic test, the maximum positioning error is 0.39 m in X axis, 0.34 m in Y axis. Finally, the reason for adopting the Z-fixed KPI algorithm is explained by the horizontal dilution of precision (HDOP), meanwhile, the influence of the known initialization point error on indoor positioning accuracy is analyzed, when a deviation from -1.5 m to 0.9 m is added to the Z-axis of the KPI, the maximum positioning error is 0.311 m in X axis, 0.08 m in Y axis; when the horizontal deviation tolerance of the KPI is set from - 0.5 m to 0.5 m, the maximum horizontal positioning error is less than 0.5 m.
Highlights
With the development of LBS in urban area, the indoor positioning system has been getting a lot of attention in the academic and commercial fields
We developed the Z-fixed Known Point Initialization (KPI) algorithm based on the high-precision carrier phase and Doppler measurements to calculate the velocity of receiver, the receiver position of current epoch is computed by the position of previous epoch, the speed of current epoch and the time interval of the observation
The time synchronization is not required in this system since the same clock drift of pseudolites can be estimated as an unknown parameter
Summary
With the development of LBS in urban area, the indoor positioning system has been getting a lot of attention in the academic and commercial fields. Gan et al.: New Array Pseudolites Technology for High Precision Indoor Positioning support dynamic positioning and has only a 4m×4m positioning coverage area Another multi-channel pseudolite called the GNSS repeater has been proposed by Niwa [11]–[14], which realizes indoor positioning using carrier phase difference method with the base and rover stations. The new method has two advantages: first, it does not need to solve the integer ambiguity, has less computation and is suitable for smartphones; second, the centimeter-level positioning can be achieved by using the high precision Doppler and carrier phase observation. Position and speed of receiver are computed on smartphone processors
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