1,720,989 research outputs found
Characterization of dual frequency GNSS observations from Xiaomi Mi 8 smartphone in absence of duty cycle
No full textBeginning in May 2016 after Google announced that the GNSS raw measures (Global Navigation Satellite System) acquired by smartphones equipped with Android would be freely accessible, a real race began for scientists to achieve of centimeter accuracy using smartphone. A further acceleration took place in May 2018 with the appearance of the first dual-frequency GNSS chip-set the Broadcom BCM47755. The manufacturer Xiaomi marketed the first mobile phone equipped with this chip-set; for the first time smartphone users had access to raw double-frequency GNSS measurements from more than one satellite system. Unfortunately, the duty cycle technique, necessary to safeguard battery life, degraded the quality of the measurements acquired by the smartphone. The last milestone reached came with the release of the Android Pie operating system which makes it possible to switch off the duty cycle. Thus the use of high-precision techniques such as Real Time Kinematic (RTK) or Precise Point Positioning with the measurements acquired by the smartphone became possible. However, in order to use these techniques, it is necessary that the quality of the measurements is not too low. Therefore, it is very important to conduct an analysis to assess their quality. The results obtained show that the second frequency offers measurements that are much less sensitive to multipath, while the signal to noise ratio of the measurements is on average above 30 dB/Hz, guaranteeing a good quality. The results of the analysis conducted show that the quality of the measurements acquired by the smartphone has reached a quality sufficient to be able to use PPP or RTK techniques
Performance assessment of GNSS single point positioning with recent smartphones
No full textThe new generation of Android smartphones are equipped with high performance Global Navigation Satellite System (GNSS) chips. These new chips are capable of tracking dual frequency multi constellation data. Moreover, starting from version 9 of Android users can disable the duty cycle power saving option, thus it is feasible to acquire good quality raw carrier-phase measurements. Nevertheless, there is still a need to evaluate the accuracy, which may be reached with current smart devices in a standard navigational solution. In this work we assessed the performance of GPS + Galileo single point positioning of three recent smartphones, namely Xiaomi Mi 8, Xiaomi Mi 9 and Huawei P30. The best positioning accuracy, in terms of horizontal root mean square error (DRMS), was obtained by Huawei P30 with a DRMS of 4.46 m. Xiaomi MI8 shows very similar performance (4.56 m of DRMS) but these results were subject to outliers. Finally Xiaomi Mi9 shows a DRMS of 7.26 m, and therefore demonstrates the poorest accuracy among tested smart devices
Structure-from-Motion 3D Reconstruction of the Historical Overpass Ponte della Cerra: A Comparison between MicMac® Open Source Software and Metashape®
Full text linkIn recent years, the performance of free-and-open-source software (FOSS) for image processing has significantly increased. This trend, as well as technological advancements in the unmanned aerial vehicle (UAV) industry, have opened blue skies for both researchers and surveyors. In this study, we aimed to assess the quality of the sparse point cloud obtained with a consumer UAV and a FOSS. To achieve this goal, we also process the same image dataset with a commercial software package using its results as a term of comparison. Various analyses were conducted, such as the image residuals analysis, the statistical analysis of GCPs and CPs errors, the relative accuracy assessment, and the Cloud-to-Cloud distance comparison. A support survey was conducted to measure 16 markers identified on the object. In particular, 12 of these were used as ground control points to scale the 3D model, while the remaining 4 were used as check points to assess the quality of the scaling procedure by examining the residuals. Results indicate that the sparse clouds obtained are comparable. MicMac® has mean image residuals equal to 0.770 pixels while for Metashape® is 0.735 pixels. In addition, the 3D errors on control points are similar: the mean 3D error for MicMac® is equal to 0.037 m with a standard deviation of 0.017 m, whereas for Metashape®, it is 0.031 m with a standard deviation equal to 0.015 m. The present work represents a preliminary study: a comparison between software packages is something hard to achieve, given the secrecy of the commercial software and the theoretical differences between the approaches. This case study analyzes an object with extremely complex geometry; it is placed in an urban canyon where the GNSS support can not be exploited. In addition, the scenario changes continuously due to the vehicular traffic
Assessment of dual frequency GNSS observations from a Xiaomi Mi 8 android smartphone and positioning performance analysis
Full text linkOn May 2018 the world’s first dual-frequency Global Navigation Satellite System (GNSS) smartphone produced by Xiaomi equipped with a Broadcom BCM47755 chip was launched. It is able to receive L1/E1/ and L5/E5 signals from GPS, Galileo, Beidou, and GLONASS (GLObal NAvigation Satellite System) satellites. The main aim of this work is to achieve the phone’s position by using multi-constellation, dual frequency pseudorange and carrier phase raw data collected from the smartphone. Furthermore, the availability of dual frequency raw data allows to assess the multipath performance of the device. The smartphone’s performance is compared with that of a geodetic receiver. The experiments were conducted in two different scenarios to test the smartphone under different multipath conditions. Smartphone measurements showed a lower C/N0 and higher multipath compared with those of the geodetic receiver. This produced negative effects on single-point positioning as showed by high root mean square error (RMS). The best positioning accuracy for single point was obtained with the E5 measurements with a DRMS (horizontal root mean square error) of 4.57 m. For E1/L1 frequency, the 2DRMS was 5.36 m. However, the Xiaomi Mi 8, thanks to the absence of the duty cycle, provided carrier phase measurements used for a static single frequency relative positioning with an achieved 2DRMS of 1.02 and 1.95 m in low and high multipath sites, respectively
Low-Cost Hardware PPP-RTK AR Time-to-Fix and Positioning Performance Assessment: A Preliminary Static Test
No full textOver the last years, researchers are struggling to develop solutions and services for smart and sustainable urban mobility creating dynamic shared spaces for both vehicles and pedestrians. Also, the deployment of autonomous vehicles has boosted the interest in precise, accurate, and robust position, navigation, and timing (PNT). Most of these services will be based primarily on the location of the vehicle relative to other vehicles, objects, and pedestrians in its vicinity. Therefore, the importance of a robust, ubiquitous, and reliable PNT can’t be overlooked. In the mass-market scenario, the challenge will be developing low-cost navigation equipment capable of providing navigation solutions that meet the accuracy, integrity, continuity, and availability requirements. This paper reports some preliminary tests aiming to investigate the phase-ambiguity fixing performance of a commercial precise point positioning real-time kinematic (PPP-RTK) correction service, employing a low-cost receiver. To assess the ambiguity resolution performance, we forced the receiver to restart the ambiguity search generating enough samples for statistic analysis. In this test, PPP-RTK has revealed a promising technique for decimetre-level accuracy positioning with low-cost receivers. Integer ambiguity fixed solutions reveal a DRMS of 0.09 m whereas float solutions reveal a DRMS of 0.45 m. When PPP-RTK corrections are not available, SPP/DGNSS solutions reveal a DRMS of 1.36 m. The test showed that the employment of cost-effective equipment along with the exploitation of correction services allows reaching decimetre/sub-metre accuracy in about 20 s and sub-decimetre accuracy in about 2 min once the integer ambiguity is fixed
Low-cost GNSS software receiver performance assessment
Full text linkThe Software-Defined Receiver (SDR) is a rapidly evolving technology which is a useful tool for researchers and allows users an extreme level customization. The main aim of this work is the assessment of the performance of the combination consisting of the Global Navigation Satellite Systems software receiver (GNSS-SDR), developed by CTTC (Centre Tecnològic de Telecomunicacions de la Catalunya), and a low-cost front-end. GNSS signals were acquired by a Nuand bladeRF x-40 front-end fed by the TOPCON PG-A1 antenna. Particular attention was paid to the study of the clock-steering mechanism due to the low-cost characteristics of the bladeRF x-40 clock. Two different tests were carried out: In the first test, the clock-steering algorithm was activated, while in the second, it was deactivated. The tests were conducted in a highly degraded scenario where the receiver was surrounded by tall buildings. Single-Point and Code Differential positioning were computed. The achieved results show that the steering function guarantees the availability of more solutions, but the DRMS is quite the same in the two tests
Developing a low-cost GNSS/IMU data fusion platform for boat navigation
No full textMethods of measuring a vessel's motioninvolve the use of expensive and complex Inertial Navigation Systems (INS). Cargo or passenger transport ships can afford the implementation of such systems while private small boat market has been cut off. The alternatives for small boat INS navigation are few. This paper investigates the potentiality of GNSS/IMU data fusion, experimenting low-cost hardware like Aceinna openIMU 300ZI and a GNSS receiver based on u-blox ZED-F9P module. The final goal is to build a lowcost self-powered system and assess the performance in small boats navigation tests. To address this goal the INS shall be light-weight, cost-effective, and easy to- install
Testing a GNSS software receiver for end-user utilization
No full textSoftware Defined Receivers(SDR) can be a very useful tools both for researchers and surveyors since it is capable of extreme customization allowing user to access, visualize and modify signal processing blocks. In this paper we test the single point performance of the GNSS-SDR software receiver coupled with Nuand BladeRF x40 front-end feeded by an active u-blox GNSS antenna powered by a bias-tee needful to provide external gain. Four different tests have been carried out in two different scenarios located in Naples (Italy) employing two different antennas: the first dataset was acquired in a site expected to be a low-multipath environment while the second in a strong multipath scenario in Centro Direzionale (CDN) site using the same instrumentation. Both tests were carried out with two different antennas. Results achieved show how SDR is a good candidate to represent an innovative low-cost and flexible platform which can be used to get intermediate frequency data useful in the field of GNSS reflectometry and ionospheric scintillation analysis
Positioning Domain Assessment of Multi Constellation Dual Frequency Lowcost Receivers in an Highly Degraded Scenario
No full textThe objective of this paper is to test in a degraded environment the performances of two different type of low-cost GNSS receivers. The first one is a typical low-cost hardware: the u-blox ZED-F9P GNSS module interfaced with u-center evaluation and a commercial front-end while the second one is a Software-Defined Receiver (SDR) software developed by Centre Tecnològic Telecomunicacions Catalunya coupled with a Nuand BladeRF x40. In order to investigate the performance of the hardware involved we applied our analysis to the measurements captured in a strong multipath scenario. Four different tests have been carried out employing the two receivers and coupled with two different antennas. Results achieved shows that the employment of the more performing antenna leads to better positioning results. The DRMS (Distance Root Mean Square) of horizontal position errors decreases of about the 54% and the 40% for the SDR and the u-blox, respectively. Nonetheless, the Nuand bladeRF shows poor positioning results with respect to those obtained with u-blox. The results achieved shows that Nuand is not yet suitable for surveying purposes. The reason resides in the poor quality of the reference clock of the on-board oscillator that doesn’t assure an appropriate stability
Low-Cost GNSS and PPP-RTK: Investigating the Capabilities of the u-blox ZED-F9P Module
No full textGNSS has become ubiquitous in high-precision applications, although the cost of high-end GNSS receivers remains a major obstacle for many applications. Recent advances in GNSS receiver technology have led to the development of low-cost GNSS receivers, making high-precision positioning available to a wider range of users. One such technique for achieving high-precision positioning is Precise Point Positioning-Real Time Kinematic (PPP-RTK). It is a GNSS processing technique that combines the PPP and RTK approaches to provide high-precision positioning in real time without the need for a base station. In this work, we aim to assess the performance of the low-cost u-blox ZED-F9P GNSS module in PPP-RTK mode using the low-cost u-blox ANN-MB antenna. The experiment was designed to investigate both the time it takes the receiver to resolve the phase ambiguity and to determine the positioning accuracies achievable. Results showed that the u-blox ZED-F9P GNSS module could achieve centimeter-level positioning accuracy in about 60 s in PPP-RTK mode. These results make the PPP-RTK technique a good candidate to fulfill the demand for mass-market accurate and robust navigation since uses satellite-based corrections to provide accurate positioning information without the need for a local base station or network. Furthermore, due to its rapid acquisition capabilities and accurate data georeferencing, the technique has the potential to serve as a valuable method to improve the accuracy of the three-S techniques (GIS, remote sensing, and GPS/GNSS)
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