1,721,135 research outputs found
A GNSS low-cost RTK network: positioning and atmospheric monitoring performances in mountain areas
No full textThe utilization of low-cost devices for global navigation satellite system (GNSS) positioning has become a widespread practice globally. Numerous studies have delved into examining the use of these devices, aiming to assess their performances, unique characteristics, and potential challenges. In recent years, the focus has extended beyond pure positioning to applications in environmental monitoring, particularly in estimating atmospheric biases such as tropospheric delay. This study concentrates on harnessing continuous operating reference station (CORS) networks for GNSS positioning at elevated altitudes, evaluating the attainable precision and robustness. Additionally, particular analyses are made to tropospheric estimations derived from rover devices through post-processing applications. While these approaches have often been implemented in the past using networks composed of geodetic receivers, this study has considered the Centipede RTK network, consisting exclusively of low-cost devices. Two different types of rovers are considered: a professional-grade and a low-cost one, aiming to analyze the achievable performances and differences between them. Three different test sites have been selected, ranging from an altitude of approximately 1470 m to 2540 m in a mountainous area close to Turin (NW Italy). After some analyses and comments based on the obtained results, some future perspectives are provided for the readers
GNSS positioning using mobile devices with the android operating system
Full text linkThe access and the use of the global navigation satellite system (GNSS) pseudo-range and carrier-phase measurements mobile devices as smartphones and tablets with an Android operating system has transformed the concept of accurate positioning with mobile devices. In this work, the comparison of positioning performances obtained with a smartphone and an external mass-market GNSS receiver both in real-time and post-processing is made. Particular attention is also paid to accuracy and precision of positioning results, also analyzing the possibility of estimating the phase ambiguities as integer values (fixed positioning) that it is still challenging for mass-market devices. The precisions and accuracies obtained with the mass-market receiver were about 5 cm and 1 cm both for real-time and post-processing solutions, respectively, while those obtained with a smartphone were slightly worse (few meters in some cases) due to the noise of its measurements
Assessing Material Impacts in NLOS UWB Ranging Errors: Characterization for Museum Environments
Full text linkMuseums, with their intricate layouts and diverse materials, present unique challenges for accurate indoor positioning, especially in environments rich with glass and other reflective surfaces. These materials can interfere with many positioning technologies, complicating efforts to track visitor movement accurately for insights into visitor behavior, exhibit engagement, and space utilization. Indoor positioning technologies have become essential for understanding movement and interaction within enclosed spaces, especially in environments like museums, where optimizing visitor experience and curators exhibit management are key priorities. While several technologies have been applied in museums, Ultra-wideband (UWB) positioning has emerged as a standout solution due to its high accuracy and resilience in complex indoor environments. This study exploits low-cost UWB positioning devices to track and analyze visitor behavior within a museum characterized by extensive glass and reflective surfaces. Through a comprehensive measurement campaign with volunteer participants visiting a real exhibition, real-time data on visitor trajectories, engagement patterns, and interactions with exhibits were collected. The UWB raw data, acquired from actual visitor movements, allows us to post-process them and propose solutions to overcome challenges posed by the glassy and crowded environment. The results show the capability of the algorithm to enable robust and reliable tracking even in challenging spatial configurations. The study’s findings highlight patterns in visitor flow, high-engagement zones, and preferred pathways, offering insights into optimizing exhibit layout and visitor satisfaction. This research underscores the potential of UWB positioning to generate actionable, data-driven insights in museum environments, supporting informed decisions in crowd management, exhibit arrangement, and personalized visitor experiences
Smartphones for 3d model reconstruction
No full textToday, it is possible to get three-dimensional information about the environment in the form of point clouds in a quick and easy way thanks to various types of existing sensors, like Laser Imaging Detection and Ranging (LiDAR), Red Green and Blues (RGB), Red-Green-Blue-Depth (RGB-D) sensors etc.., but also smartphones. Unlike the past, when the three-dimensional data acquisition tools were very expensive, they required to carefully planning the survey and they were used mainly by experienced users, today these sensors are widely available on the mass market at low prices allowing to get suitable results for different types of applications. Smartphones can now be easily mounted on UAV (Unmanned Aerial Vehicle) and UGV (Unmanned Ground Vehicle) systems in such a way that, potentially, anyone can access the data acquisition and extraction of 3D information, and, the advantage of using these techniques lies in the fact that it is possible to exploit the radiometric information contained in 2D image pixels using different strategies, like stereo matching and the structure from motion approach. Since, in recent years, smartphones devices have had a great improvement and the embedded sensors are becoming more efficient in terms of accuracy and reliability, this chapter attempts to analyse the complexity of the use of these kind of sensors for 3D reconstruction, but which require a lot of a priori knowledge of the internal sensors (e.g. camera calibration, data extraction, etc..) to reach stable results (e.g. camera calibration, data extraction, etc..). It will be briefly described how these technologies are categorized with the aim of highlighting the differences of the final products obtained according to the sensors used and of evaluating their performances in different environments
Loosely coupled GNSS and UWB with INS integration for indoor/outdoor pedestrian navigation
Full text linkThe growth of location-based services (LBS) has increased rapidly in last years, mainly due to the possibility to exploit low-cost sensors installed in portable devices, such as smartphones and tablets. This work aims to show a low-cost multi-sensor platform developed by the authors in which an ultra-wideband (UWB) indoor positioning system is added to a classical global navigation satellite systems–inertial navigation system (GNSS-INS) integration, in order to acquire different synchronized data for further data fusion analysis in order to exploit seamless positioning. The data fusion is based on an extended Kalman filter (EKF) and on a geo-fencing approach which allows the navigation solution to be provided continuously. In particular, the proposed algorithm aims to solve a navigation task of a pedestrian user moving from an outdoor space to an indoor environment. The methodology and the system setup is presented with more details in the paper. The data acquired and the real-time positioning estimation are analysed in depth and compared with ground truth measurements. Particular attention is given to the UWB positioning system and its behaviour with respect to the environment. The proposed data fusion algorithm provides an overall horizontal and 3D accuracy of 35 cm and 45 cm, respectively, obtained considering 5 different measurement campaigns
Laying the foundation for an artificial neural network for photogrammetric riverine bathymetry
Full text linkThis work aims to test the effectiveness of artificial intelligence for correcting water refraction in shallow inland water using very high-resolution images collected by Unmanned Aerial Systems (UAS) and processed through a total FOSS workflow. The tests focus on using synthetic information extracted from the visible component of the electromagnetic spectrum. An artificial neural network is created using data of three morphologically similar alpine rivers. The RGB information, the SfM depth and seven radiometric indices are calculated and stacked in an 11-bands raster (input dataset). The depths are calculated as the difference between the Up component of the bathymetry cross-sections and the water surface quotas and constitute the dependent variable of the regression. The dataset is then scaled. The observations of one of the analyzed case studies are used as the unseen dataset to test the generalization capability of the model. The remaining observations are divided into test (20%) and training (80%) datasets. The generated NN is a 3-layer MLP model with one hidden layer and the Rectified Linear Unit (ReLU) and sigmoid activation functions. The weights are initialized to small Gaussian random values, and kernel regularizers, L1 and L2, are added to reduce the overfitting. Weights are updated with the Adam search technique, and the mean squared error is the loss function. The importance and significance of 11 variables are assessed. The model has a 0.70 r-squared score on the test dataset and 0.77 on the training dataset. The MAE is 0.06 and the RMSE 0.08, similar results obtained from the unseen dataset. Although the good metrics, the model shows some difficulties generalizing swallow depths
Single-Baseline RTK Positioning Using Dual-Frequency GNSS Receivers Inside Smartphones
Full text linkGlobal Navigation Satellite System (GNSS) positioning is currently a common practice thanks to the development of mobile devices such as smartphones and tablets. The possibility to obtain raw GNSS measurements, such as pseudoranges and carrier-phase, from these instruments has opened new windows towards precise positioning using smart devices. This work aims to demonstrate the positioning performances in the case of a typical single-base Real-Time Kinematic (RTK) positioning while considering two different kinds of multi-frequency and multi-constellation master stations: a typical geodetic receiver and a smartphone device. The results have shown impressive performances in terms of precision in both cases: with a geodetic receiver as the master station, the reachable precisions are several mm for all 3D components while if a smartphone is used as the master station, the best results can be obtained considering the GPS+Galileo constellations, with a precision of about 2 cm both for 2D and Up components in the case of L1+L5 frequencies, or 3 cm for 2D components and 2 cm for the Up, in the case of an L1 frequency. Moreover, it has been demonstrated that it is not feasible to reach the phase ambiguities fixing: despite this, the precisions are still good and also the obtained 3D accuracies of positioning solutions are less than 1 m. So, it is possible to affirm that these results are very promising in the direction of cooperative positioning using smartphone devices
Positioning exploiting GNSS raw measurements
No full textPosition and navigation are key advancements of smartphones technology. Nowadays, any smartphone is equipped with a GNSS chip, providing the device position and time. On one side, the improvements in electronics and communications boosted the design of smaller, cheaper and power saving GNSS chips, which are now multi-constellation and multi-frequency and outperform dedicated personal positioning devices. On the other side, the availability of accurate position and time enabled the development of services and location-based applications making the smartphone a professional positioning instrument. Starting from 2016, Android smartphones provide a set of raw GNSS measurements, inaddition to the user position, which open the way to more advanced and customizable positioning algorithms. This chapter first gives an overview on GNSS, then introduces the use of GNSS in smartphones, including the latest developments. Finally, examples of positioning performances, obtained exploiting raw GNSS measurements, are reported
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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