Two-Step Self-Calibration of LiDAR-GPS/IMU Based on Hand-Eye Method

Multi-line LiDAR and GPS/IMU are widely used in autonomous driving and robotics, such as simultaneous localization and mapping (SLAM). Calibrating the extrinsic parameters of each sensor is a necessary condition for multi-sensor fusion. The calibration of each sensor directly affects the accurate positioning control and perception performance of the vehicle. Through the algorithm, accurate extrinsic parameters and a symmetric covariance matrix of extrinsic parameters can be obtained as a measure of the confidence of the extrinsic parameters. As for the calibration of LiDAR-GPS/IMU, many calibration methods require specific vehicle motion or manual calibration marking scenes to ensure good constraint of the problem, resulting in high costs and a low degree of automation. To solve this problem, we propose a new two-step self-calibration method, which includes extrinsic parameter initialization and refinement. The initialization part decouples the extrinsic parameters from the rotation and translation part, first calculating the reliable initial rotation through the rotation constraints, then calculating the initial translation after obtaining a reliable initial rotation, and eliminating the accumulated drift of LiDAR odometry by loop closure to complete the map construction. In the refinement part, the LiDAR odometry is obtained through scan-to-map registration and is tightly coupled with the IMU. The constraints of the absolute pose in the map refined the extrinsic parameters. Our method is validated in the simulation and real environments, and the results show that the proposed method has high accuracy and robustness

Two-Step Self-Calibration of LiDAR-GPS/IMU Based on Hand-Eye Method

Multi-line LiDAR and GPS/IMU are widely used in autonomous driving and robotics, such as simultaneous localization and mapping (SLAM). Calibrating the extrinsic parameters of each sensor is a necessary condition for multi-sensor fusion. The calibration of each sensor directly affects the accurate positioning control and perception performance of the vehicle. Through the algorithm, accurate extrinsic parameters and a symmetric covariance matrix of extrinsic parameters can be obtained as a measure of the confidence of the extrinsic parameters. As for the calibration of LiDAR-GPS/IMU, many calibration methods require specific vehicle motion or manual calibration marking scenes to ensure good constraint of the problem, resulting in high costs and a low degree of automation. To solve this problem, we propose a new two-step self-calibration method, which includes extrinsic parameter initialization and refinement. The initialization part decouples the extrinsic parameters from the rotation and translation part, first calculating the reliable initial rotation through the rotation constraints, then calculating the initial translation after obtaining a reliable initial rotation, and eliminating the accumulated drift of LiDAR odometry by loop closure to complete the map construction. In the refinement part, the LiDAR odometry is obtained through scan-to-map registration and is tightly coupled with the IMU. The constraints of the absolute pose in the map refined the extrinsic parameters. Our method is validated in the simulation and real environments, and the results show that the proposed method has high accuracy and robustness

State updating in a distributed hydrological model by ensemble Kalman filtering with error estimation

For flood simulation in small- and medium-sized catchments, discharge observations may be used to update model states of a distributed hydrological model to improve performance. The ensemble Kalman filter (EnKF) has been widely used for hydrological assimilation due to its relative simplicity and robustness. An advantage of the EnKF is that it is easy to include different sources of uncertainty, therefore the choice of error model is crucial for the application of the EnKF assimilation. This paper describes an EnKF assimilation scheme for estimating error models using the maximum a posteriori estimation method (MAP). We test this scheme in two small and medium-sized catchments in China with different characteristics, and in addition compared the performance differences under two kinds of rainfall forcing. We show that MAP is beneficial in specifying error models and providing reliable ensemble spread. The assimilation scheme can effectively ameliorate the degradation of distributed hydrological model performance due to uncalibrated model parameters and/or poor quality of input data

From the Quadrangle to the River: Revitalizing the Heart of Downtown Springfield

This studio report explores community service learning in the graduate urban design studio taught in the in Department of Landscape Architecture and Regional Planning at the University of Massachusetts Amherst and instructed by Professor Frank Sleegers. The project will began with a visioning workshop, conducted to engage community members in the shaping of project goals and objectives within the project area of downtown Springfield. These findings were brought to the studio and guided the design process and outcomes. Five design teams developed five alternative master plans for the core area of downtown Springfield with focus on the revitalization of open space and the connection of the urban axis from the Quadrangle to the Connecticut River. These five design strategies are recommendations to improve the livability of the heart of downtown Springfield for employers, employees, residents, and visitors. Remarkable for this studio was a simultaneous collaboration with another Landscape Architecture Studio and an Architecture Studio at the University of Massachusetts Amherst. These studios were coordinated through the UMass Amherst Design Center that was launched in the spring of 2010. The public response to the work of the three studios resulted in the reopening of Pynchon Plaza – a pocket park in the axis of the Quadrangle to the River that had been closed down for 35 years

Acupuncture on GB34 for immediate analgesia and regulating pain-related anxiety for patients with biliary colic: a protocol of randomized controlled trial

Abstract Background Biliary colic (BC) is a frequent hepatobiliary disorder encountered in emergency departments. Acupuncture may be effective as an alternative and complementary medicine for BC. Nonetheless, rigorous trials investigating its efficacy are lacking. Therefore, the aim of this study protocol is to determine whether acupuncture provides immediate relief of pain and associated symptoms in BC patients. Method Eighty-six participants who aged from 18 to 60 years with BC will be recruited in the First People's Hospital of Longquanyi District, Chengdu (West China Longquan Hospital Sichuan University). All participants will be allocated into two treatment groups including acupuncture group and sham acupuncture group using a 1:1 ratio. Each group will only receive a single 30-min needle treatment while waiting for their test results after completing the routine examination for BC. The primary outcome of the study is to assess the change in pain intensity after the 30-min acupuncture treatment. The secondary outcomes of the study include the change in pain intensity at various time points, the degree of gastrointestinal symptoms at different time points, the level of anxiety experienced during pain episodes at different time points, the score of Pain Anxiety Symptoms Scale-20 (PASS-20), the score of Fear of Pain Questionnaire-III (FPQ-III), and the score of Pain Catastrophizing Scale (PCS), among others. Discussion The results of this research will provide substantial evidence regarding the efficacy of acupuncture in alleviating symptoms associated with BC. Trial registration ClinicalTrials.gov, ChiCTR2300070661. Registered on 19 April 2023

Fairmount Greenway - A Community Initative

This studio was based on the Fairmount Greenway that was developed through a series of public meetings with the neighborhood community and with consultants from the firm Crosby, Schlessinger and Smallridge (CSS). The Fairmount Greenway, while drawing its identity from the traditional greenway model is in fact a reinterpretation of an urban greenway. The greenway path follows along both primary and secondary city streets because of the lack of space along the rail right-of-way. The Fairmount Greenway begins at what will be a new station stop at New Market South Bay near Upham’s Corner in northern Dorchester. The greenway follows adjacent to the Indigo transit line, the commuter rail that connects South Boston communities with South Station situated in proximity to Boston’s central business and tourist districts. The greenway corridor, like the transit line, stretches along a strong central north-south axis but does not follow a straight line. Instead the greenway veers east and west through Dorchester, Mattapan and Hyde Park crossing the Indigo line at Ceylon Park, Geneva Avenue, Washington Street, under the historic Woodrow Avenue Bridge, Morton Street and River Street near the Neponset River Greenway. The greenway terminates at the Readville Station in Hyde Park. Secondary auxiliary loops extend from the central corridor connecting various recreational, cultural and economic sites with the greenway. These extensions also connect with the greater regional green space network, which will be described more in detail in the assessment to come. The defining third component of the Fairmount Greenway is the periodic greenspaces that fall along the greenway corridor. Some of these public spaces currently exist as parklands and community gardens; others are primarily publicly owned vacant lots that are planned for future development