Metrological evaluation of vessel-based mobile lidar for survey of coastal structures

Surveying of coastal structures is necessary to ensure that the structures are in good operating condition. Mobile lidar systems could be installed on vessels to monitor the coastal structures, even if there is no previous metrological information about their reliability. The aim of this work is to perform the metrological verification of the mentioned survey instruments. The verification methodology is based on the comparison of mobile lidar data from a breakwater with ground truth data provided by a Riegl LMS Z390i terrestrial lidar. Mobile lidar data are obtained from an Optech Lynx system installed on a vessel. The results show errors lower than 0.09 m based on distance measurements. Universal Transverse Mercator (UTM) coordinates show absolute errors lower than 0.12 m in the horizontal plane and 0.18 m in height. Precision analysis from the mobile lidar shows error values up to 0.055 m, while the terrestrial lidar gives 0.018 m for the same region of interest. The spatial resolution from the mobile lidar gives values of 321 points m^?2, in comparison with the 22,013 points m^?2 from the terrestrial lidar. Two point clouds from the same region of the breakwaters, obtained using the mobile and the terrestrial lidar, were triangulated and rasterized. The standard deviation of the vertical distances between the nodes of the raster data shows a value of 0.064 m. The results obtained show the potential of mobile lidar systems in combination with vessels for the monitoring of certain coastal structures, such as breakwaters, sea walls, bridges, wharves, and jetties.     

Electronic mobile guides: a survey

Mobile tourist guides have been in the spot light for the past decade and are becoming increasingly available in various forms to tourists visiting places. The majority of these mobile tourist guides are to be used via a constant network connection and some as proprietary standalone mobile applications installed on-device. Some are solely navigational assistants using positioning technologies for large cities offering exploratory services and others are used indoors, for example as museum guides. This research paper attempts to categorize these mobile guides using a detailed set of evaluation criteria in order to extract design principles which can be used by application designers and developers.     

Automated extraction of street-scene objects from mobile lidar point clouds

Mobile laser scanning or lidar is a new and rapid system to capture high-density three-dimensional (3-D) point clouds. Automatic data segmentation and feature extraction are the key steps for accurate identification and 3-D reconstruction of street-scene objects (e.g. buildings and trees). This article presents a novel method for automated extraction of street-scene objects from mobile lidar point clouds. The proposed method first uses planar division to sort points into different grids, then calculates the weights of points in each grid according to the spatial distribution of mobile lidar points and generates the geo-referenced feature image of the point clouds using the inverse-distance-weighted interpolation method. Finally, the proposed method transforms the extraction of street-scene objects from 3-D mobile lidar point clouds into the extraction of geometric features from two-dimensional (2-D) imagery space, thus simplifying the automated object extraction process. Experimental results show that the proposed method provides a promising solution for automatically extracting street-scene objects from mobile lidar point clouds.     

Control of truck-trailer mobile robots: a survey

Mobile robots with trailers and its control is one of the most challenging problems in service robotics. Since, these kinds of robots can accomplish the given task in a faster and cheaper way than an individual robot, they find applications in many areas. However, the backward movement of a truck-trailer mobile robot is more complex as the complete system is highly non-linear and unstable. The practical advantages of this system in the transportation industry have led to significant research in this area. Various studies have been conducted in this area for exploring more on the subject of non-linear control. This paper presents a survey on the various control strategies developed in the backward motion of mobile robot with trailers. The existing studies in this field are analyzed to identify unsolved problems.     

The structural and radiative consistency of three-dimensional tree reconstructions from terrestrial lidar

A novel methodology is proposed to reconstruct 3D tree architectures from terrestrial LiDAR (TLiDAR) scans. The methodology is robust and relatively insensitive to wind- and occlusion-induced artefacts in the 3D TLiDAR point clouds. A quantitative evaluation of structural attributes, like the vertical foliage and wood area profiles, as well as the shoot orientation distribution, was performed. Due to the difficulties of acquiring reliable and accurate estimates of these parameters in the field, an original evaluation approach was chosen that reproduces the TLiDAR scanning and subsequent tree reconstruction process in a virtual environment. In a second step the reconstructed tree models were ingested in a validated 3D radiative transfer model to simulate both their reflectance signatures (observable by space borne instruments) and directional transmission properties (measurable during field campaigns) under various spectral, illumination and tree density scenarios. The results of these evaluations confirm the appropriateness of the proposed tree reconstruction model for the generation of structurally and radiatively faithful copies of existing plant and canopy architectures.     

Vision for mobile robot navigation: a survey

Surveys the developments of the last 20 years in the area of vision for mobile robot navigation. Two major components of the paper deal with indoor navigation and outdoor navigation. For each component, we have further subdivided our treatment of the subject on the basis of structured and unstructured environments. For indoor robots in structured environments, we have dealt separately with the cases of geometrical and topological models of space. For unstructured environments, we have discussed the cases of navigation using optical flows, using methods from the appearance-based paradigm, and by recognition of specific objects in the environment     

Ergonomic survey of mobile cranes

A mobile crane survey was pursued for two years in conjunction with the Construction Industry Training Board. Information was collected on mobile cranes of the wheel and track type. Operational tasks were studied together with interactions which affect the optimum performance of the system in relation to the site organisation in which they form a part. Visits to site were made during working hours, under prevailing weather conditions, and to plant hire companies in the South Wales area. Appendices detail noise exposures in crane cabins and an audiological survey of crane drivers and others.     

Automating the evaluation of urban roadside drainage systems using mobile lidar data

Roadside channel systems are critical for the management of stormwater runoff and the protection of the structural integrity of roads; and thus, require systematic evaluation and maintenance. However, the evaluation of these systems remains ad hoc due to the lack of efficient inspection methods. This paper contributes to filling this gap by providing an automated process for the inspection and evaluation of roadside channel systems using data obtained from mobile lidar (Light Detection and Ranging) scanners. The Cloth Simulation Filtering algorithm was employed to split lidar point clouds into bare earth and object datasets, and then compute six key attributes of roadside channels based on the bare earth dataset. The six attributes are: channel depth, bottom width, side slope, longitudinal slope, and length and density of subsurface pipes and culverts. To test and demonstrate the new automated process, it was applied to six street sections in the City of Houston, Texas. The computed attributes were compared to the design and maintenance guidelines set by the City of Houston and Harris County. The evaluation results indicate that every channel examined in this study has its own condition issues and improvement needs. While no channel section in this study was in full compliance with the guidelines, no channel was utterly incompatible either. The results show that the developed automated process can effectively and efficiently evaluate roadside channels, providing an alternative to conventional manual inspection methods. Future work could use the output of the developed method to assess the risk of localized flooding and inform both the municipal government and property owners about effective mitigation measures.     

Video streaming distribution over mobile Internet: a survey

In recent times, mobile Internet has witnessed the explosive growth of video applications, embracing user-generated content, Internet Protocol television (IPTV), live streaming, video-on-demand, video conferencing, and FaceTime-like video communications. The exponential rise of video traffic and dynamic user behaviors have proved to be a major challenge to video resource sharing and delivery in the mobile environment. In this article, we present a survey of state-of-the-art video distribution solutions over the Internet. We first discuss the challenges of mobile peer-to-peer (MP2P)-based solutions and categorize them into two groups. We discuss the design idea, characteristics, and drawbacks of solutions in each group.We also give a reviewfor solutions of video transmission in wireless heterogeneous networks. Furthermore, we summarize the information-centric networking (ICN)-based video solutions in terms of in-network caching and name-based routing. Finally, we outline the open issues for mobile video systems that require further studies.     

Development of a mobile three-dimensional scanning lidar system for aerosol monitoring in rural areas in Greece

A mobile three-dimensional scanning M1E LIDAR system, suitable to perform daytime/night-time measurements of aerosol parameters (backscatter ratio, extinction coefficient profile) in the Planetary Boundary Layer (PBL) is described. The retrieving algorithm used will be able to retrieve aerosols' extinction and backscattering profiles up to 4-6km, in moderately polluted areas is investigated and discussed     

Identification of pole-like structures from mobile lidar data of complex road environment

Pole-like structures (PLSs) located in road environment are important roadway assets. They play a vital role in road safety inspection and road planning. The use of light detection and ranging (lidar) based mobile mapping technology for mapping of PLSs is an important area of research as it holds the potential for automation. Point cloud data of rural, peri-urban, and urban road environment are used in this study, which pose special challenge in view of the complexity of terrain, unlike well-planned roads, which have been the subject of interest in existing literature for identification of PLSs. A new five-step method is proposed in this article. The first two steps, i.e. ground filtering and voxelization of filtered non-ground points, are used for data size reduction. Next three steps are used to extract PLSs from reduced data. The proposed method was tested on point cloud data of three test sites having different levels of complexities. PLSs including partially occluded pole, tilted pole, pole situated very close to other objects, and vertical pole attached to tilted pole were accurately identified. Average correctness and completeness, respectively of 92.6% and 94.9%, were achieved in three different complex test sites, i.e. urban, peri-urban, and rural sites, respectively. Computation complexity shows that our proposed method delivers fast and computationally efficient solution for identifying the PLSs from volumetric mobile lidar point cloud. Impact of PLSs on road safety and road planning is also addressed for these selected test sites.     

地面数字电视广播和移动通信的汇聚

介绍了地面数字电视广播和移动通信汇聚的方式和趋势,讨论IP数据广播技术和体系架构,分析了欧洲的陆地数字视频广播标准DVB-T和最新的适用于手持移动终端的DVB-H的优点和存在的问题并概要介绍了中国目前的地面数字电视广播标准,最后指出在移动设备中发展视频广播尚需解决的问题。     

Privacy in targeted advertising on mobile devices: a survey

Targeted advertising has transformed the marketing landscape for a wide variety of businesses, by creating new opportunities for advertisers to reach prospective customers by delivering personalised ads, using an infrastructure of a number of intermediary entities and technologies. The advertising and analytics companies collect, aggregate, process, and trade a vast amount of users’ personal data, which has prompted serious privacy concerns among both individuals and organisations. This article presents a comprehensive survey of the privacy risks and proposed solutions for targeted advertising in a mobile environment. We outline details of the information flow between the advertising platform and ad/analytics networks, the profiling process, the measurement analysis of targeted advertising based on user’s interests and profiling context, and the ads delivery process, for both in-app and in-browser targeted ads; we also include an overview of data sharing and tracking technologies. We discuss challenges in preserving the mobile user’s privacy that include threats related to private information extraction and exchange among various advertising entities, privacy threats from third-party tracking, re-identification of private information and associated privacy risks. Subsequently, we present various techniques for preserving user privacy and a comprehensive analysis of the proposals based on such techniques; we compare the proposals based on the underlying architectures, privacy mechanisms, and deployment scenarios. Finally, we discuss the potential research challenges and open research issues.

     

Challenges of computing in mobile cellular environment—a survey

Advances in cellular mobile technology have engendered a new paradigm of computing, called mobile computing. The frequency spectrum allocated to this service is not sufficient with respect to enormous growth of mobile communication users. Tracking down a mobile user in a cellular network which is a collection of geometric areas called cells each serviced by a base station is the other concern to the designer. This service also needs another problem to be solved, that is the access of common information by mobile users. Other than the issues in existing technology, many other issues on developing technology need to be addressed.

The survey is done in two phases. In the first phase a survey of three fundamental problems in mobile computing on existing technology is done. The issues discussed arise from three essential requirements: the efficient management and sharing of the spectrum among the users; to locate a mobile user in the cellular mobile environments; and processing of queries on location dependent data. The second phase highlights on research on different issues such as security, routing etc. in third generation wireless network in developing technology.     

A survey of theories for mobile agents

This paper presents a comparative survey of formalisms related to mobile agents. It describes the -calculus and its extensions, the Ambient calculus, Petri nets, Actors, and the family of generative communication languages. Each of these formalisms defines a mathematical framework that can be used to reason about mobile code; they vary greatly in their expressiveness, in the mechanisms they provide to specify mobile code based applications and in their practical usefulness for the validation and the verification of such applications. In this paper we show how these formalisms can be used to represent the mobility and communication aspects of two mobile code environments: Obliq and Messengers. We compare and classify the different formalisms with respect to mobility and discuss some shortcomings and desirable extensions. We also point to other emerging concepts in formalisms for mobile code systems.     

Accuracy analysis in mobile robot machining of large-scale workpiece

Mobile robot machining provides more flexible machining mode compared to the robot machining with a fixed base. However, its machining accuracy is frequently questioned. This paper focuses on the accuracy analysis in mobile robot machining. To evaluate the machining error qualitatively, the tool center point (TCP) error index is defined as the distance between the TCP and the designed machining point. The different error sources acting on the TCP error index are enumerated, and the theoretical accuracy analysis is proposed to eliminate the TCP error. The mobile robot machining strategy is then proposed based on the accuracy analysis. To ensure high machining accuracy, the global measurement system locates the position of the workpiece and the mobile platform. The force-controlled grinding head is used to compensate the TCP error. Experimental results show that the TCP error during mobile robot machining is lower than 40 mm, which mainly introduced by the calibration of the workpiece. The force-controlled grinding head can compensate the TCP error and the fluctuation of the grinding force under the control is lower than ±2 N.     

自主移动机器人足球比赛视觉定位方法综述

综述了RoboCup足球赛中全自主移动机器人基于视觉的定位技术,包括机器人自定位和多机器人协作物体定位.介绍了定位技术的发展情况与分类.从机器人环境构建形式的不同以及先验位姿和概率方法的应用与否等方面,系统地分析和比较了各种自定位方法.对于多机器人协作物体定位,阐述了静态方法和动态跟踪方法.总结了定位过程中需要重点研究的传感器模型构建、图像处理、特征匹配以及协作过程涉及的相关问题.最后就视觉定位存在的问题和技术发展趋势进行了讨论.     

Comparative analysis of a mobile device and paper as effective survey tools

Universal Access in the Information Society - As mobile devices, such as e-book readers and tablet computers, have emerged as alternatives to traditional printed media, they are also being...     

Quantitative assessment of mobile web guidelines conformance

Conformance metrics for the mobile web can play a crucial role as far as engineering mobile websites are concerned, especially if they are automatically obtained. In this way, developers can have an idea in numeric terms of how suitable their developments are for mobile devices. However, there are a plethora of devices with their own particular features (screen size, formats support, etc.) that restrict a unified automatic assessment process. This paper proposes a tool-supported method for device-tailored assessment in terms of conformance with Mobile Web Best Practices 1.0, including the definition of five quantitative metrics for automatically measuring mobile web conformance: Navigability, Page layout, Page definition, User input and Overall score. The behaviour of these metrics was analysed for different devices and different web paradigms, both mobile web pages and their equivalent desktop pages. As expected, the results show that mobile web pages on more capable devices score higher. In addition, 20 users took part in an experiment aimed at discovering how conformance-based scores relate to usability dimensions. The results demonstrate that automatic scoring approaches strongly correlate with usability scores obtained by direct observation, such as task completion time and user satisfaction. This correlation is even stronger for the device-tailored assessment than the one that assumes a general profile for all devices. For instance, results show a strong negative correlation between Overall score and task completion time: ρ (9) = −0.81, (p < 0.05) for the generalist approach and ρ (9) = −0.88 for the device-tailored one, entailing that mobile web guidelines and the metrics based on their conformance capture usability aspects. This result challenges the widely accepted belief that conformance to guidelines does not imply more usable web pages, at least for web accessibility conformance.     

Quality of TOPSAR topographic data for volcanology studies at Kilauea Volcano, Hawaii: An assessment using airborne lidar data

We use airborne lidar data for the summit area of Kilauea Caldera, Hawaii, to explore the utility of topographic data collected by the TOPSAR airborne interferometric radar for volcanology studies. The lidar data are processed to a spatial resolution of 1 m/pixel, compared to TOPSAR with a spatial resolution of 5 m. Over a variety of fresh volcanic surfaces (pahoehoe and aa lava flows, ash falls and fluvial fans), TOPSAR data are shown to have a typical vertical offset compared to the lidar data of no more than ∼2-3 m. Larger differences between the two data sets and TOPSAR data drop-outs are found to be concentrated around steep scarps such as the walls of pit craters and ground cracks associated with the Southwest Rift Zone. A comparison of these two data sets is used to explore the utility of TOPSAR to interpret the topography of volcanic features close to the spatial resolution of TOPSAR, such as spatter ramparts, fractures, a perched lava flow, and eroded ash deposits. Comparison of the TOPSAR elevation and the lidar first-return minus the return from the ground surface (the so-called “bald Earth” data) for vegetated areas reveals TOPSAR penetration into the tree canopy is typically at least 10% and no more than ∼50%, although a wide range of penetration values from 0% to 90% has been identified. Our results are significant because they show that TOPSAR data for volcanoes can reliably be used to measure regional slopes and the thickness of lava flows, and have value for the validation of coarser spatial resolution digital elevation data (such as SRTM) in areas where lidar data have not been collected.