Recent advances in mobile mapping systems have greatly enhanced the efficiency and convenience of acquiring urban 3D data. These systems utilize LiDAR sensors mounted on vehicles to capture vast ...cityscapes. However, a significant challenge arises due to occlusions caused by roadside parked vehicles, leading to the loss of scene information, particularly on the roads, sidewalks, curbs, and the lower sections of buildings. In this study, we present a novel approach that leverages deep neural networks to learn a model capable of filling gaps in urban scenes that are obscured by vehicle occlusion. We have developed an innovative technique where we place virtual vehicle models along road boundaries in the gap-free scene and utilize a ray-casting algorithm to create a new scene with occluded gaps. This allows us to generate diverse and realistic urban point cloud scenes with and without vehicle occlusion, surpassing the limitations of real-world training data collection and annotation. Furthermore, we introduce the Scene Gap Completion Network (SGC-Net), an end-to-end model that can generate well-defined shape boundaries and smooth surfaces within occluded gaps. The experiment results reveal that 97.66% of the filled points fall within a range of 5 centimeters relative to the high-density ground truth point cloud scene. These findings underscore the efficacy of our proposed model in gap completion and reconstructing urban scenes affected by vehicle occlusions.
GNSS/INS applications are being developed, especially for direct georeferencing in airborne photogrammetry. Achieving accurately georeferenced products from the integration of GNSS and INS requires ...removing systematic errors in the mobile mapping systems. The INS sensor's uncertainty is decreasing; therefore, the influence of the deflection of verticals (DOV, the angle between the plumb line and normal to the ellipsoid) should be considered in the direct georeferencing. Otherwise, an error is imposed for calculating the exterior orientation parameters of the aerial images and aerial laser scanning. This study determines the DOV using the EGM2008 model and gravity data in Sweden. The impact of the DOVs on horizontal and vertical coordinates, considering different flight altitudes and camera field of view, is assessed. The results confirm that the calculated DOV components using the EGM2008 model are sufficiently accurate for aerial mapping system purposes except for mountainous areas because the topographic signal is not modelled correctly.
Résumé
Les applications GNSS/INS se développent, notamment pour le géoréférencement direct en photogrammétrie aéroportée. Pour obtenir des produits géoréférencés avec précision grâce à l'intégration du GNSS et de l'INS, il faut éliminer les erreurs systématiques des systèmes de cartographie mobile. L'incertitude du capteur INS est de plus en plus faible; par conséquent, l'influence de la déviation de la verticale (DOV, l'angle entre le fil à plomb et la normale à l'ellipsoïde) doit être prise en compte dans le géoréférencement direct. Autrement, une erreur est commise dans le calcul des paramètres d'orientation externe des images aériennes et du balayage laser aérien. Cette étude détermine les DOV en utilisant le modèle EGM2008 et les données gravimétriques en Suède. L'impact des DOV sur les coordonnées horizontales et verticales est évalué en considérant différentes altitudes de vol et différents champs de vision de la caméra. Les résultats confirment que les composantes DOV calculées à l'aide du modèle EGM2008 sont suffisamment précises pour les systèmes de cartographie aérienne, sauf pour les zones montagneuses où le signal topographique n'est pas modélisé correctement.
Zusammenfassung
GNSS/INS‐Anwendungen entwickeln sich, insbesondere für die direkte Georeferenzierung in der luftgestützten Photogrammetrie. Um präzise georeferenzierte Produkte aus der Integration von GNSS und INS zu erhalten, müssen systematische Fehler in den mobilen Kartierungssystemen beseitigt werden. Die Unsicherheit des INS‐Sensors nimmt ab; Daher sollte der Einfluss der Abweichung von Vertikalen (DOV, der Winkel zwischen der Lotlinie und der Normalen zum Ellipsoid) bei der direkten Georeferenzierung berücksichtigt werden. Andernfalls wird ein Fehler für die Berechnung der äußeren Orientierungsparameter der Luftbilder und der Luftlaserabtastung auferlegt. Diese Studie bestimmt die DOV unter Verwendung des EGM2008‐Modells und Schwerkraftdaten in Schweden. Der Einfluss der DOVs auf horizontale und vertikale Koordinaten unter Berücksichtigung verschiedener Flughöhen und Kamerasichtfelder wird bewertet. Die Ergebnisse bestätigen, dass die berechneten DOV‐Komponenten unter Verwendung des EGM2008‐Modells ausreichend genau für Luftkartierungssysteme sind, mit Ausnahme der Berggebiete, da das topografische Signal nicht korrekt modelliert wird.
Resumen
Se desarrollan aplicaciones GNSS/INS, especialmente para georreferenciación directa en fotogrametría aérea. Lograr productos georreferenciados con precisión a partir de la integración de GNSS e INS requiere eliminar errores sistemáticos en los sistemas de cartografía móvil. Al reducirse la incertidumbre del sensor INS, la influencia de la deflexión de la vertical (DOV, el ángulo entre la plomada y la normal al elipsoide) requiere ser considerada en la georreferenciación directa. De lo contrario, los parámetros de orientación exterior de las imágenes aéreas y/o el escaneo láser aéreo tendrán un error sistemático debido a la DOV. Este estudio determina el DOV usando el modelo EGM2008 y datos de gravedad en Suecia. Se evalúa el impacto de la DOV en las coordenadas horizontales y verticales, considerando diferentes altitudes de vuelo y campo de visión de la cámara. Los resultados confirman que los componentes del DOV calculados con el modelo EGM2008 son lo suficientemente precisos para los sistemas de cartografía aérea, excepto en zonas montañosas porque la componente topográfica no se modela correctamente.
摘要
GNSS/INS的应用正在发展中，特别是用于机载摄影测量的直接地理参考。要从GNSS和INS的整合中实现精确的地理参考产品，需要消除移动测绘系统中的系统误差。由于INS传感器的不确定性在下降，因此，在直接地理参考中应考虑垂直方向的偏差（DOV，铅垂线与椭圆体法线之间的角度）的影响。否则，在计算航空影像和航空激光扫描的外部方位参数时就会出现误差。本研究使用EGM2008模型和瑞典的重力数据来确定DOV。考虑到不同的飞行高度和相机视场，评估了DOV对水平和垂直坐标的影响。结果证实，使用EGM2008模型计算的DOV分量对于航测目的是足够准确的，但山区除外，因为地形信号没有被正确建模。
This paper aims to study and quantify the induced error due to the deflection of verticals (DOV) when integrating different sensors, focusing on GNSS and INS for 3D mapping in airborne mapping.
It is shown that the DOV effect should be considered for direct georeferencing because the DOV components are in the order of (or larger than) INS uncertainty.
The results also show that other parameters affect the horizontal and vertical coordinates like camera field of view, flight direction and flight altitude.
The growing interest and the market for indoor Location Based Service (LBS) have been drivers for a huge demand for building data and reconstructing and updating of indoor maps in recent years. The ...traditional static surveying and mapping methods can't meet the requirements for accuracy, efficiency and productivity in a complicated indoor environment. Utilizing a Simultaneous Localization and Mapping (SLAM)-based mapping system with ranging and/or camera sensors providing point cloud data for the maps is an auspicious alternative to solve such challenges. There are various kinds of implementations with different sensors, for instance LiDAR, depth cameras, event cameras, etc. Due to the different budgets, the hardware investments and the accuracy requirements of indoor maps are diverse. However, limited studies on evaluation of these mapping systems are available to offer a guideline of appropriate hardware selection. In this paper we try to characterize them and provide some extensive references for SLAM or mapping system selection for different applications. Two different indoor scenes (a L shaped corridor and an open style library) were selected to review and compare three different mapping systems, namely: (1) a commercial Matterport system equipped with depth cameras; (2) SLAMMER: a high accuracy small footprint LiDAR with a fusion of hector-slam and graph-slam approaches; and (3) NAVIS: a low-cost large footprint LiDAR with Improved Maximum Likelihood Estimation (IMLE) algorithm developed by the Finnish Geospatial Research Institute (FGI). Firstly, an L shaped corridor (2nd floor of FGI) with approximately 80 m length was selected as the testing field for Matterport testing. Due to the lack of quantitative evaluation of Matterport indoor mapping performance, we attempted to characterize the pros and cons of the system by carrying out six field tests with different settings. The results showed that the mapping trajectory would influence the final mapping results and therefore, there was optimal Matterport configuration for better indoor mapping results. Secondly, a medium-size indoor environment (the FGI open library) was selected for evaluation of the mapping accuracy of these three indoor mapping technologies: SLAMMER, NAVIS and Matterport. Indoor referenced maps were collected with a small footprint Terrestrial Laser Scanner (TLS) and using spherical registration targets. The 2D indoor maps generated by these three mapping technologies were assessed by comparing them with the reference 2D map for accuracy evaluation; two feature selection methods were also utilized for the evaluation: interactive selection and minimum bounding rectangles (MBRs) selection. The mapping RMS errors of SLAMMER, NAVIS and Matterport were 2.0 cm, 3.9 cm and 4.4 cm, respectively, for the interactively selected features, and the corresponding values using MBR features were 1.7 cm, 3.2 cm and 4.7 cm. The corresponding detection rates for the feature points were 100%, 98.9%, 92.3% for the interactive selected features and 100%, 97.3% and 94.7% for the automated processing. The results indicated that the accuracy of all the evaluated systems could generate indoor map at centimeter-level, but also variation of the density and quality of collected point clouds determined the applicability of a system into a specific LBS.
Review of mobile mapping and surveying technologies Puente, I.; González-Jorge, H.; Martínez-Sánchez, J. ...
Measurement : journal of the International Measurement Confederation,
08/2013, Letnik:
46, Številka:
7
Journal Article
Recenzirano
Mobile surveying is currently one of the most popular topics in the LiDAR industry. The collection of highly precise point cloud data is provided by laser scanning systems on moving platforms with an ...integrated navigation solution. The potential of LiDAR based mobile surveying technology is now well proven. This article introduces an analysis on the current performance of some outstanding mobile terrestrial laser scanning systems. In this work, an overview of the positioning, scanning and imaging devices integrated into these systems is also presented. As part of this study, a systematic comparison of the navigation and LiDAR specifications provided by the manufacturers is provided. Our review suggests that mobile laser scanning systems can mainly be divided into two categories (mapping and surveying) depending on their final purpose, accuracy, range and resolution requirements. A refined integrated analysis based on hardware components could be expected to cause further improvements on these results.
This paper presents a feature-based simultaneous localization and mapping (SLAM) system for panoramic image sequences obtained from a multiple fisheye camera rig in a wide baseline mobile mapping ...system (MMS). First, the developed fisheye camera calibration method combines an equidistance projection model and trigonometric polynomial to achieve high-accuracy calibration from the fisheye camera to an equivalent ideal frame camera, which warrants an accurate transform from the fisheye images to a corresponding panoramic image. Second, we developed a panoramic camera model, corresponding bundle adjustment with a specific back propagation error function, and linear pose initialization algorithm. Third, the implemented feature-based SLAM pipeline consists of several specific strategies and algorithms in initialization, feature matching, frame tracking, and loop closing to overcome the difficulties in tracking wide baseline panoramic image sequences. We conducted experiments on large-scale MMS datasets of more than 15 km trajectories and 14,000 panoramic images as well as small-scale public video datasets. Our results show that the developed panoramic SLAM system PAN-SLAM can achieve fully-automatic camera localization and sparse map reconstruction in both small-scale indoor and large-scale outdoor environments including challenging scenes (e.g., dark tunnel) without the aid of any other sensors. The localization accuracy, which was measured by the absolute trajectory error (ATE), resembled the high-accuracy GNSS/INS reference of 0.1 m. PAN-SLAM also outperformed several feature-based fisheye and monocular SLAM systems with incomparable robustness in various environments. The system could be considered as a robust complementary solution and an alternative to expensive commercial navigation systems, especially in urban environments where signal obstruction and multipath interference are common. Source code and demo are available at http://study.rsgis.whu.edu.cn/pages/download/.
This paper presents the results of a complex three-dimensional reconstruction of the church of Nuestra Señora de la Asunción (Ávila, Spain) as an example of a successful process of verticalization ...from point clouds to a comprehensive computer-aided design (CAD) model. The reconstruction was carried out using the novel and advanced wearable mobile mapping system ZEB-REVO in combination with a lifting pole, in order to cover the whole geometry of the temple and, also, to model the different constructive elements. To this end, a set of good practices was followed, which allowed for passing from reality to the CAD model, such as the use of closed loops or even the use of different parametric and non-parametric strategies to capture the real geometry of the elements. As a result, this paper outlines the main guidelines for passing from point clouds to comprehensive CAD models, the former being useful for the application of smart preventive conservation processes, heritage building information models or even advanced numerical simulations.
Street trees are important components of an urban green space and understanding and measuring their ecological and cultural services is crucial for assessing the quality of streets and managing urban ...environments. Currently, most studies mainly focus on evaluating the ecological services of street trees by measuring the amount of greenness, but how to evaluate their aesthetic functions through quantitative measurements of street trees remain unclear. To address this problem, we propose a method to assess the aesthetic functions of street trees by quantifying the shape of greenness inspired by assessments of skyline aesthetics. Using a state-of-the-art mobile mapping system, we collected downtown-wide lidar data and panoramic images in Jinzhou City, Hebei Province, China. We developed a method for extracting the canopy line from the mobile lidar data, and then identified two basic elements, peaks and gaps, from street canopy lines and extracted six indexes (i.e., richness of peaks, evenness of peaks, frequency of peaks, total length of gaps, evenness of gaps and frequency of gaps) to describe the fluctuations and continuities of street canopy lines. We analyzed the abundance and spatial distribution of these indexes together with survey responses on the streets’ aesthetics and found that most of them were significantly correlated with human perception of streets. Compared to indexes of amount of greenness (e.g., green volume and green view index), these shape indexes have stronger influences on the physical aesthetic beauty of street trees. These findings suggest that a comprehensive assessment of the aesthetic function of street trees should consider both shape and amount of greenness. This study provides a new perspective for the assessment of urban green spaces and can assist future urban greening planning and urban landscape management.
Accurate three-dimensional (3D) data from indoor spaces are of high importance for various applications in construction, indoor navigation and real estate management. Mobile scanning techniques are ...offering an efficient way to produce point clouds, but with a lower accuracy than the traditional terrestrial laser scanning (TLS). In this paper, we first tackle the problem of how the quality of a point cloud should be rigorously evaluated. Previous evaluations typically operate on some point cloud subset, using a manually-given length scale, which would perhaps describe the ranging precision or the properties of the environment. Instead, the metrics that we propose perform the quality evaluation to the full point cloud and over all of the length scales, revealing the method precision along with some possible problems related to the point clouds, such as outliers, over-completeness and misregistration. The proposed methods are used to evaluate the end product point clouds of some of the latest methods. In detail, point clouds are obtained from five commercial indoor mapping systems, Matterport, NavVis, Zebedee, Stencil and Leica Pegasus: Backpack, and three research prototypes, Aalto VILMA , FGI Slammer and the Würzburg backpack. These are compared against survey-grade TLS point clouds captured from three distinct test sites that each have different properties. Based on the presented experimental findings, we discuss the properties of the proposed metrics and the strengths and weaknesses of the above mapping systems and then suggest directions for future research.
This work presents an approach for the preventive conservation of historical constructions by means of Historical Building Information Modelling (HBIM) strategies. To this end, the methodology ...exploits the latest advances in inspection protocols, digitalization tools -by means of the novel back-pack mapping systems- as well as wireless monitoring networks. All this information is integrated in the HBIM environment by using ad-hoc families and interoperable communication protocols that allow obtaining a complete knowledge of the conservation status of the site. Additionally, the approach uses key performance indicators in order to evaluate the environmental conditions of the different assets presented in the site. All these features have been validated in one of the most representative heritage buildings in Spain: The General Historical Library of the University of Salamanca.
•A novel HBIM platform for heritage preventive conservation is presented.•The combination of IoT and remote sensing strategies is exploited for conservation.•KPI has been introduced inside the HBIM environment.•A wearable mobile mapping system is used for generate the as-built model.•The protocol is validated in one of the most outstanding heritage building in Spain.
Mobile mapping systems, which are equipped with a laser scanner, panoramic camera, and inertial navigation system, can flexibly and efficiently obtain precision point clouds. However, these systems ...require re-installation for each mission, which causes displacement errors in the instruments, resulting in discrepancies between multiple collections of data. The existing calibration methods usually require additional control targets settled in a managed field survey. Furthermore, the point clouds obtained with mobile mapping systems do not follow the common assumption of rigid transformation. To alleviate the above problems, we propose a flexible in-situ calibration method that only requires data collected in a round-trip survey pattern and conducts a self-calibration of the placement parameters with meticulously designed exact point matching. Specifically, because the accuracy of the existing feature-based registration method is not sufficient to acquire the exact correspondences of point clouds and to prune the outliers in correspondence searching. We propose novel pruning and refining approaches to obtain exact point-to-point correspondences between the round-trip point clouds. From systematic analyses of the coupling between different factors, we then construct a simplified error model that takes into account the a priori rotation- and translation-weighted observations. Finally, to alleviate the correlation effects between different parameters, we decouple the least-squares solver into several stages and obtain robust self-calibration parameters. Surveying experiments show that the flexible calibration method proposed in this paper is both effective and feasible in improving the accuracy of point clouds in overlapping areas, and can reduce the inconsistency of the calibrated point clouds by 37.02%.
•Exact point-to-point correspondences under round-trip mobile mapping systems point clouds.•Reliable and stable self-calibration strategy with multi-stage optimization.•A flexible targetless self-calibration method without additional control points.
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