Ultra-low power anti-crosstalk collision avoidance light detection and ranging using chaotic pulse position modulation approach

A novel concept of collision avoidance single-photon light detection and ranging（LIDAR） for vehicles has been demonstrated, in which chaotic pulse position modulation is applied on the transmitted laser pulses for robust anti-crosstalk purposes. Besides, single-photon detectors（SPD） and time correlated single photon counting techniques are adapted, to sense the ultra-low power used for the consideration of compact structure and eye safety. Parameters including pulse rate, discrimination threshold, and number of accumulated pulses have been thoroughly analyzed based on the detection requirements, resulting in specified receiver operating characteristics curves. Both simulation and indoor experiments were performed to verify the excellent anti-crosstalk capability of the presented collision avoidance LIDAR despite ultra-low transmitting power.

A new approach of single epoch GPS posi- tioning for landslide monitoring

When the deformation of landslide becomes larger, the conventional static GPS surveying cannot satisfy the real-time requirement in landslide monitoring. In this paper we present a new method for single epoch GPS posi- tioning combining with the accuracy of approximate coordinates of monitored station in landslide monitoring. This algorithm does not consider troublesome cycle-slip problem of carrier phase, and integer ambiguities can be solved at a single epoch, so the centimeter level accurate coordinates can be calculated instantaneously. By means of fil- tering or smoothing, this method can be extended to detect millimeter level deformation and velocity. In order to test the new method, low-cost single frequency receivers have been used in a real landslide, which happened in Jiangxi Province, China.

A state‑domain robust autonomous integrity monitoring with an extrapolation method for single receiver positioning in the presence of slowly growing fault

Single receiver positioning has been widely used as a standard and standalone positioning technique for about 25 years.To detect the slowly growing faults caused by satellite and receiver clocks in single receiver positioning,the Autonomous Integrity Monitoring with an Extrapolation method(AIME)was proposed based on the Kalman filter measurement domain.However,AIME was designed with the assumption of there is the same number of visible satellites at each epoch,which limits its application.To address this issue,this paper proposes a state-domain Robust Autonomous Integrity Monitoring with the Extrapolation Method(SRAIME).The slowly growing fault detection statistics is established based on the difference between the estimates of the state propagator and the posterior state estimation in Kalman filtering.Meanwhile,singular value decomposition is adopted to factor the covariance matrix of the difference to increase computational robustness.Besides,the relevant formulas of the proposed method are theoretically derived,and it is proven that the proposed method is suitable for any positioning model based on the Kalman filter.Additionally,the results of two experiments indicate that SRAIME can detect slowly growing faults in single receiver positioning earlier than AIME.

Precision position measurement of single atom

Atom localization in a five-level atomic system under the effect of three driving fields and one standing wave field is suggested. A spontaneously emitted photon from the proposed system is measured in a detector. Precision position measurement of an atom is controlled via phase and vacuum field detuning without considering the parity violation.

Analysis of Galileo signal-in-space range error and positioning performance during 2015-2018

A long-term analysis of signal-in-space range error (SISRE) is presented for all healthy Galileo satellites, and the first pair of full operational capability satellites in wrong elliptical orbits. Both orbit and clock errors for Galileo show an obvious convergence trend over time. The annual statistical analyses show that the average root mean squares (RMSs) of SISRE for the Galileo constellation are 0.58 m (2015), 0.29 m (2016), 0.23 m (2017), and 0.22 m (2018). Currently, the accuracy of the Galileo signal-in-space is superior to that of the global positioning system (GPS) Block IIF (0.35 m). In addition, the orbit error accounts for the majority of Galileo SISRE, while the clock error accounts for approximately one-third of SISRE due to the high stability of the onboard atomic clock. Single point positioning results show that Galileo achieves an accuracy of 2-3 m, which is comparable to that of GPS despite the smaller number of satellites and worse geometry. Interestingly, the vertical accuracy of Galileo, which uses the NeQuick ionospheric model, is higher than that of GPS. Positioning with single frequency E1 and E5 show a higher precision than E5a and E5b signals. Regarding precise point positioning (PPP), the results indicate that a comparable positioning accuracy can be achieved among different stations with the current Galileo constellation. For static PPP, the RMS values of Galileo-only solutions are within 1 cm horizontally, and the vertical RMSs are mostly within 2 cm horizontally. For kinematic PPP, the RMSs of Galileo-only solutions are mostly within 4 cm horizontally and 6 cm vertically.