scholarly journals Velocity-Preserving Trajectory Compression Based on Retrace Point Detection

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Anbang Chen ◽  
Linfeng Liu
Keyword(s):  
Mobile Devices ◽  
Compression Ratio ◽  
Smart Phones ◽  
Navigation Systems ◽  
Measured Velocity ◽  
Compression Algorithms ◽  
Position Errors ◽  
Spatiotemporal Information ◽  
Simulation Results ◽  
Point Detection

With the increasing development of GPS-equipped mobile devices such as smart phones and vehicle navigation systems, the trajectories containing valuable spatiotemporal information are recorded. Typically, plenty of trajectory records are generated and stored, making the device memory suffer a heavy storage pressure. Thus, it is a vital issue to compress the trajectories. The trajectory semantics are usually ignored or reduced in traditional trajectory compression techniques. In addition, most of existing trajectory compression algorithms only concern the position errors rather than the velocity errors of trajectories. This paper proposes a velocity-preserving trajectory compression algorithm based on retrace point detection (VPTC-RP) that can compress a set of trajectories by removing unnecessary redundancy points, while the skeleton of these trajectories is maintained as much as possible. In VPTC-RP, the retrace points and the velocity errors are taken to reflect the speeds and directions attached with the points. VPTC-RP first determines the retrace points based on the changed movement directions, and then, the retrace points are extracted from the original trajectories. Especially, the retrace points are put in a buffer, and the subtrajectories in the buffer are compressed according to the measured velocity errors. Simulations are carried out on the Geolife trajectory dataset, and the simulation results indicate that VPTC-RP can achieve a preferable tradeoff among the compression error, compression ratio, and running time.

FEATURES OF CONSTRUCTION OF ON-BOARD HELICOPTER RADAR ICE EXPLORATION ON BASIS OF CIRCULAR GROUND SURFACE WITH SYNTHESIS OF APERTURE ROTATING ANTENNA

2019 ◽  
pp. 31-37
Author(s):  
I. G. Antсev ◽  
A. P. Aleshkin ◽  
V. V. Vladimirov ◽  
E. O. Kudrina ◽  
O. L. Polonchik ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Ground Surface ◽  
Rotor Blades ◽  
Navigation Systems ◽  
Propeller Blade ◽  
Antenna Aperture ◽  
Sensing System ◽  
Radar Systems ◽  
Simulation Results ◽  
Circular Antenna Array

The results of modeling the processes of receiving and processing the signals of remote sensing of the Earth’s surface using helicopter radar and synthesizing the antenna aperture due to its placement on the rotating rotor blades are presented. The mathematical correctness of the application of the developed algorithms for processing probing signals, as well as the uniqueness of the measurements, was confirmed. At the same time, the dimensions of the synthesized aperture due to the rotation of the radiator placed at the end of the propeller blade are equivalent to a circular antenna array with a diameter of tens of meters. The functionality of the remote sensing system based on this radar meets the requirements for ice observation and navigation systems for seagoing ships off the coast. The simulation results confirm the promise of further research in this direction and can be used in the development of radar systems with synthesized antenna aperture mounted on rotating rotor blades.

Secure Examination Management System for M-Learning (SEMS)

2017 ◽  
Vol 2 (2) ◽  
pp. 31-35
Author(s):  
Akshada Abnave ◽  
Charulata Banait ◽  
Mrunalini Chopade ◽  
Supriya Godalkar ◽  
Soudamini Pawar ◽  
...  
Keyword(s):  
Face Recognition ◽  
Social Interactions ◽  
Mobile Devices ◽  
Management System ◽  
Mobile Apps ◽  
Smart Phones ◽  
Examination System ◽  
Open Environment ◽  
Exchange Information ◽  
Personal Mobile Devices

M-learning or mobile learning is defined as learning through mobile apps, social interactions and online educational hubs via Internet or network using personal mobile devices such as tablets and smart phones. However, in such open environment examination security is most challenging task as students can exchange mobile devices or also can exchange information through network during examination. This paper aims to design secure examination management system for m- learning and provide appropriate mechanism for anti- impersonation to ensure examination security. The users are authenticated through OTP. To prevent students from exchanging mobile devices during examination, system re-authenticates students automatically through face recognition at random time without interrupting the test. The system also provides external click management i.e. prevent students from accessing online sites and already downloaded files during examination.

scholarly journals Consistency of the Empirical Distributions of Navigation Positioning System Errors with Theoretical Distributions—Comparative Analysis of the DGPS and EGNOS Systems in the Years 2006 and 2014

Sensors ◽  
2020 ◽  
Vol 21 (1) ◽  
pp. 31
Author(s):  
Mariusz Specht
Keyword(s):  
Normal Distribution ◽  
Root Mean Square ◽  
Statistical Tests ◽  
Position Error ◽  
Positioning System ◽  
Navigation Systems ◽  
Mean Square ◽  
Positioning Systems ◽  
Position Errors ◽  
System Errors

Positioning systems are used to determine position coordinates in navigation (air, land and marine). The accuracy of an object’s position is described by the position error and a statistical analysis can determine its measures, which usually include: Root Mean Square (RMS), twice the Distance Root Mean Square (2DRMS), Circular Error Probable (CEP) and Spherical Probable Error (SEP). It is commonly assumed in navigation that position errors are random and that their distribution are consistent with the normal distribution. This assumption is based on the popularity of the Gauss distribution in science, the simplicity of calculating RMS values for 68% and 95% probabilities, as well as the intuitive perception of randomness in the statistics which this distribution reflects. It should be noted, however, that the necessary conditions for a random variable to be normally distributed include the independence of measurements and identical conditions of their realisation, which is not the case in the iterative method of determining successive positions, the filtration of coordinates or the dependence of the position error on meteorological conditions. In the preface to this publication, examples are provided which indicate that position errors in some navigation systems may not be consistent with the normal distribution. The subsequent section describes basic statistical tests for assessing the fit between the empirical and theoretical distributions (Anderson-Darling, chi-square and Kolmogorov-Smirnov). Next, statistical tests of the position error distributions of very long Differential Global Positioning System (DGPS) and European Geostationary Navigation Overlay Service (EGNOS) campaigns from different years (2006 and 2014) were performed with the number of measurements per session being 900’000 fixes. In addition, the paper discusses selected statistical distributions that fit the empirical measurement results better than the normal distribution. Research has shown that normal distribution is not the optimal statistical distribution to describe position errors of navigation systems. The distributions that describe navigation positioning system errors more accurately include: beta, gamma, logistic and lognormal distributions.

An Improved and Efficient Algorithm for SINS/GPS/Doppler Integrated Navigation Systems

2012 ◽  
Vol 245 ◽  
pp. 323-329 ◽  
Author(s):  
Muhammad Ushaq ◽  
Jian Cheng Fang
Keyword(s):  
Kalman Filter ◽  
Navigation System ◽  
Inertial Navigation System ◽  
Inertial Sensor ◽  
Inertial Navigation ◽  
Measurement Unit ◽  
Navigation Systems ◽  
Integrated Navigation ◽  
Efficient Manner ◽  
Position Errors

Inertial navigation systems exhibit position errors that tend to grow with time in an unbounded mode. This degradation is due, in part, to errors in the initialization of the inertial measurement unit and inertial sensor imperfections such as accelerometer biases and gyroscope drifts. Mitigation to this growth and bounding the errors is to update the inertial navigation system periodically with external position (and/or velocity, attitude) fixes. The synergistic effect is obtained through external measurements updating the inertial navigation system using Kalman filter algorithm. It is a natural requirement that the inertial data and data from the external aids be combined in an optimal and efficient manner. In this paper an efficient method for integration of Strapdown Inertia Navigation System (SINS), Global Positioning System (GPS) and Doppler radar is presented using a centralized linear Kalman filter by treating vector measurements with uncorrelated errors as scalars. Two main advantages have been obtained with this improved scheme. First is the reduced computation time as the number of arithmetic computation required for processing a vector as successive scalar measurements is significantly less than the corresponding number of operations for vector measurement processing. Second advantage is the improved numerical accuracy as avoiding matrix inversion in the implementation of covariance equations improves the robustness of the covariance computations against round off errors.

scholarly journals Optical navigation for nanosatellite star trackers

2021 ◽  
Author(s):  
Harry (Ming Qi) Zhang
Keyword(s):  
Optical Navigation ◽  
Position Errors ◽  
Compact Size ◽  
Design Case ◽  
Simulation Results ◽  
Design Case Study ◽  
Navigation Filters ◽  
Great Resolution ◽  
Key Parameter

This thesis looks at the effectiveness of using nanosatellite class star trackers to perform optical navigation. Although star trackers used for these missions lack the accuracy and sensitivity of sensors employed on larger spacecraft, they offer great resolution relative to its compact size. Two Extended Kalman Filter-based navigation filters illustrate the applications of this class of sensor. The first filter looks at horizon-based techniques using observations of Mars and its moons to assist the navigation filter in a hyperbolic approach. Results show low position (< 300 m) and velocity (< 0:15 m/s) errors as spacecraft reaches periapse. The filter formulation serves as a basis for a design case study exploring different possible sensor configurations for this mission type. The second filter looks at landmark-based techniques using absolute and relative landmarks as observations. Measurement frequency appears as a key parameter in this study, simulation results show position errors in the order of tens of kilometers, or better even if absolute landmarks are only available every 30 minutes. The accuracy of the results are validated through series of Monte Carlo simulation.

scholarly journals Mobile Geographic Information Systems

2012 ◽  
pp. 230-253
Author(s):  
Yang Li ◽  
Allan J. Brimicombe
Keyword(s):  
Information Systems ◽  
Mobile Devices ◽  
Geographical Information Systems ◽  
Business Models ◽  
Smart Phones ◽  
Geographical Information ◽  
Location Awareness ◽  
Mobile Telecommunication ◽  
Mobile Gis ◽  
Wireless Mobile

This chapter introduces the concept of Mobile Geographical Information Systems (Mobile GIS) as an evolution of conventional GIS to being available on wireless mobile devices such as smart phones. The evolution of the technology and its applications are charted in this chapter. The main elements of Mobile GIS are then discussed. This focuses on: GIS servers; wireless mobile telecommunication networks; wireless mobile devices; location-awareness technology; and gateway services. This is followed by a discussion of the main features in terms of the services and usage of Mobile GIS: mobility; real-time connectivity; location-awareness; broadened usage. Mobile Geographical Information Systems are an important facilitating technology for Location-Based Services (LBS). A range of applications of Mobile GIS for smart phones are described. The chapter closes with a discussion of the prospects and challenges for Mobile GIS. Challenges derive from four broad areas: limitations that derive from the technologies being used; areas of GIScience that still need to be adequately researched; users; and business models for a sustainable presence.

M-Learning

2014 ◽  
pp. 261-296
Author(s):  
Jean-Eric Pelet ◽  
Jashim Khan ◽  
Panagiota Papadopoulou ◽  
Emmanuelle Bernardin
Keyword(s):  
Social Media ◽  
Mobile Devices ◽  
Exploratory Study ◽  
Smart Phones ◽  
User Generated Content ◽  
Free Access ◽  
User Friendliness ◽  
Mena Region ◽  
The World ◽  
E Learning

From the perspective of improving e-learning, the free access and user friendliness of User Generated Content (UGC) tools, such as social media, embedded onto mobile devices, such as smartphones and tablets, make them attractive to be adopted by students and professors in many institutions around the world. This chapter presents the results of an exploratory study on the use of smart phones and social media, identifying differences among countries, focusing on the MENA region (Middle East and North Africa). The objective is to facilitate the understanding of the rapidly evolving and expanding technology of smart phones and social media and explore its potential for m-learning purposes. Results show that social media and mobile devices can be effectively combined in a promising way to enable m-learning.

Security in Mobile Computing

2015 ◽  
pp. 349-363
Author(s):  
Venus W. Samawi
Keyword(s):  
Operating System ◽  
Mobile Computing ◽  
Mobile Devices ◽  
Operating Systems ◽  
Mobile Device ◽  
Mobile Security ◽  
Smart Phones ◽  
Security Issues ◽  
Security Models ◽  
State Of Art

These days, peoples expected to move around carrying their mobile devices, talking to friends, completing their work, accessing emails etc. His/her pictures, work, study, even relationship (friends, and family) all is in the mobile device. Therefore, mobile devices (especially smart phones) become an ideal target for different attacks. Mobile computing also becomes important in enterprises and organizations. Therefore, it is important to illustrate the state of art on vulnerabilities and threats on mobile device. This chapter is addressed to explain mobile computing concept, features, architecture, operating systems, and risks to mobile devices. Mobile operating system structureand characteristicsare demonstrated. The author also illustrates mobile security issues, and type of threats to mobile devices. Finally, features and security models of two popular smartphone operating systems, Android and iOS, are illustrated. It was found that the security models of these two smartphones is immature and do not meet the enterprises security policies.

Location Based E-commerce System

2011 ◽  
pp. 881-892
Author(s):  
Nuno André Osório Liberato ◽  
João Eduardo Quintela Alves de Sous Varajão ◽  
Emanuel Soares Peres Correia ◽  
Maximino Esteves Correia Bessa
Keyword(s):  
Mobile Devices ◽  
System Architecture ◽  
Mobile Applications ◽  
Service Providers ◽  
Smart Phones ◽  
Search Results ◽  
Desktop Computers ◽  
Product Search ◽  
Near Future ◽  
Potential Customers

Location-based mobile services (LBMS) are at present an ever growing trend, as found in the latest and most popular mobile applications launched. They are, indeed, supported by the hasty evolution of mobile devices capabilities, namely smart phones, which are becoming truer mobile pocket-computers; by users demand, always searching for new ways to benefit from technology, besides getting more contextualized and user-centred services; and, lastly, by market drive, which sees mobile devices as a dedicated way to reach customers, providing profile-based publicity, products, discounts and events. With e-commerce, products and services started arriving to potential customers through desktop computers, where they can be bought and fast delivered to a given address. However, expressions such as “being mobile”, “always connected”, “anytime anywhere” that already characterize life in the present will certainly continue to do so in the near future. Meanwhile, mobile devices centred commerce services seem to be the next step. Therefore, this paper presents a system architecture designed for location-based e-commerce systems. These systems, where location plays the most important role, enable a remote products/services search, based in user parameters: after a product search, shops with that products are returned in the search results and are displayed in a map, around the user present location; and services like obtaining more information, reserving and purchasing are made available as well. This concept represents a mix between traditional client-oriented commerce and faceless mass-oriented e-commerce, enabling a proximity-based user-contextualized system, being well capable of conveying significant advantages and facilities to both service-providers/retailers and users.

The Estimation of Angular Misalignments for Ultra Short Baseline Navigation Systems. Part I: Numerical Simulations

2013 ◽  
Vol 66 (4) ◽  
pp. 561-578 ◽  
Author(s):  
Hsin-Hung Chen
Keyword(s):  
Numerical Simulations ◽  
Survey Method ◽  
Alignment Error ◽  
Navigation Systems ◽  
Misalignment Angle ◽  
Short Baseline ◽  
Position Errors ◽  
Positioning Errors ◽  
Line Survey ◽  
Survey Approach

Ultra Short Baseline (USBL) navigation systems are often faced with positioning errors arising from misalignments between sensors. This paper proposes a line survey method for USBL angular alignment calibration. In the scheme of USBL line survey, mathematical representations of positioning error arising from heading, pitch and roll misalignments are derived, respectively. The effect of each misalignment angle and how the differences can be used to calibrate each misalignment angle in turn are presented. An iterative algorithm that takes advantage of the geometry of position errors resulting from angular misalignments is developed for USBL calibration. Numerical simulations are provided to demonstrate the effectiveness of the USBL line survey approach. In addition, the effect of measurement error on the estimation of roll alignment error is evaluated and discussed.

Sign in / Sign up

Export Citation Format

Share Document