Systematic Error Correction for Geo-Location of Airborne Optoelectronic Platforms

In order to improve the geo-location accuracy of the airborne optoelectronic platform and eliminate the influence of assembly systematic error on the accuracy, a systematic geo-location error correction method is proposed. First, based on the kinematic characteristics of the airborne optoelectronic platform, the geo-location model was established. Then, the error items that affect the geo-location accuracy were analyzed. The installation error between the platform and the POS was considered, and the installation error of platform’s pitch and azimuth was introduced. After ignoring higher-order infinitesimals, the least square form of systematic error is obtained. Therefore, the systematic error can be obtained through a series of measurements. Both Monte Carlo simulation analysis and in-flight experiment results show that this method can effectively obtain the systematic error. Through correction, the root-mean-square value of the geo-location error have reduced from 45.65 m to 12.62 m, and the mean error from 16.60 m to 1.24 m. This method can be widely used in systematic error correction of relevant photoelectric equipment.

Pedagogical implication of Audio-Articulation Method to defossilize /e/এ/ sound in English pronunciation of Bangladeshi EFL learners

The purpose of this article is to show how to defossilize the English /e/ sound which is pronounced by the Bengali learners of English instead of /ei/ sound in such words like ape, make and day etc. This mispronunciation creates confusion among the native speakers of English and the Bengali learners’ pronunciation loses comprehensibility to the listeners. The author, in his experience, observes that Phonological fossilization of /e/ sound in the Bengali speakers of English is the main cause of this mispronunciation and incomprehensibility level in them. The present study is a detail lesson plan to defossilize the problem causing /e/ sound by using Audio Articulation Method propounded by Mehmet Demirezen in the classroom practice. As a fossilized pronunciation error correction method, the audio articulation method can play a vital role in creating awareness of a fossilized sound among the EFL learners in Bangladesh. By applying different kinds of drills, such as, conversation drills, substitution drills, question-answer drills, repetition drills, language games etc in the class hour, the teachers can endeavor to defossilize the problem causing sounds among the students and both the teachers and learners in Bangladesh can be benefited through this practice.

Relativistic Effects on Satellite–Ground Two–Way Precise Time Synchronization

An ultrahigh precise clock (space optical clock) will be installed onboard a low-orbit spacecraft (a usual expression for a low-orbit satellite operating on an orbit at an altitude of less than 1000 km) in the future, which will be expected to obtain better time-frequency performance in a microgravity environment, and provide the possible realization of ultrahigh precise long-range time synchronization. The advancement of the microwave two-way time synchronization method can offer an effective solution for developing time-frequency transfer technology. In this study, we focus on a method of precise satellite-ground two-way time synchronization and present their key aspects. For reducing the relativistic effects on two-way precise time synchronization, we propose a high-precision correction method. We show the results of tests using simulated data with fully realistic effects such as atmospheric delays, orbit errors, and earth gravity, and demonstrate the satisfactory performance of the methods. The accuracy of the relativistic error correction method is investigated in terms of the spacecraft attitude error, phase center calibration error (the residual error after calibrating phase center offset), and precise orbit determination (POD) error. The results show that the phase center calibration error and POD error contribute greatly to the residual of relativistic correction, at approximately 0.1~0.3 ps, and time synchronization accuracy better than 0.6 ps can be achieved with our proposed methods. In conclusion, the relativistic error correction method is effective, and the satellite-ground two-way precise time synchronization method yields more accurate results. The results of Beidou two-way time synchronization system can only achieve sub-ns accuracy, while the final accuracy obtained by the methods in this paper can improved to ps-level.

AR-Based Navigation Using RGB-D Camera and Hybrid Map

Current pedestrian navigation applications have been developed for the smartphone platform and guide users on a 2D top view map. The Augmented Reality (AR)-based navigation from the first-person view could provide a new experience for pedestrians compared to the current navigation. This research proposes a marker free system for AR-based indoor navigation. The proposed system adopts the RGB-D camera to observe the surrounding environment and builds a point cloud map using Simultaneous Localization and Mapping (SLAM) technology. After that, a hybrid map is developed by integrating the point cloud map and a floor map. Finally, positioning and navigation are performed on the proposed hybrid map. In order to visualize the augmented navigation information on the real scene seamlessly, this research proposes an orientation error correction method to improve the correctness of navigation. The experimental results indicated that the proposed system could provide first-person view navigation with satisfactory performance. In addition, compared to the baseline without any error correction, the navigation system with the orientation error correction method achieved significantly better performance. The proposed system is developed for the smart glasses and can be used as a touring tool.

Error correction by Reed–Solomon codes using its automorphisms

The article explores the syndrome invariants of АГ-group of automorphisms of Reed–Solomon codes (RS-codes) that are a joint group of affine and cyclic permutations. The found real invariants are a set of norms of N Г-orbits that make up one or another АГ-orbit. The norms of Г-orbits are vectors with 2 1 Cδ− coordinates from the Galois field, that are determined by all kinds of pairs of components of the error syndromes. In this form, the invariants of the АГ-orbits were cumbersome and difficult to use. Therefore, their replacement by conditional partial invariants is proposed. These quasi-invariants are called norm-projections. Norm-projection uniquely identifies its АГ-orbit and therefore serves as an adequate way for formulating the error correction method by RS-codes based on АГ-orbits. The power of the АГ-orbits is estimated by the value of N2, equal to the square of the length of the RS-code. The search for error vectors in transmitted messages by a new method is reduced to parsing the АГ‑orbits, but actually their norm-projections, with the subsequent search for these errors within a particular АГ-orbit. Therefore, the proposed method works almost N2 times faster than traditional syndrome methods, operating on the basic of the “syndrome – error” principle, that boils down to parsing the entire set of error vectors until a specific vector is found.