Current Issue : April - June Volume : 2019 Issue Number : 2 Articles : 5 Articles
Road traffic is the important driving factor for economic and social development.\nWith the rapid increase of vehicle population, road traffic problems\nsuch as traffic jam and traffic accident have become the bottleneck which restricts\neconomic development. In recent years, natural disasters frequently\noccur in China. Therefore, it is essential to extract road information to compute\nthe degree of road damage for traffic emergency management. A road\nextraction method based on region growing and mathematical morphology\nfrom remote sensing images is proposed in this paper. According to the road\nfeatures, the remote sensing image is preprocessed to separate road regions\nfrom non-road regions preliminarily. After image thresholding, region growing\nalgorithm is used to extract connected regions. Then we sort connected\nregions by area to exclude the small regions which are probably non-road objects.\nFinally, the mathematical morphology algorithm is used to fill the holes\ninside the road regions. The experimental results show that the method proposed\ncan effectively extract roads from remote sensing images. This research\nalso has broad prospects in dealing with traffic emergency management by\nthe government....
With the application of UAVs in intelligent transportation systems, vehicle\ndetection for aerial images has become a key engineering technology and has\nacademic research significance. In this paper, a vehicle detection method for\naerial image based on YOLO deep learning algorithm is presented. The method\nintegrates an aerial image dataset suitable for YOLO training by\nprocessing three public aerial image datasets. Experiments show that the\ntraining model has a good performance on unknown aerial images, especially\nfor small objects, rotating objects, as well as compact and dense objects, while\nmeeting the real-time requirements....
In this contribution, we study the phase-only ambiguity resolution and positioning\nperformance of GPS for short baselines. It is well known that instantaneous (single-epoch) ambiguity\nresolution is possible when both phase and code (pseudorange) data are used. This requires, however,\na benign multipath environment due to the severe effects multipath has on the code measurements.\nWith phase-only processing, one would be free from such severe effects, be it that phase-only\nprocessing requires a change in receiver-satellite geometry, as a consequence of which it cannot be\ndone instantaneously. It is thus of interest to know how much change in the relative receiver-satellite\ngeometry is needed to achieve successful phase-only ambiguity resolution with correspondingly high\nprecision baseline solutions. In this contribution, we study the two-epoch phase-only performance\nof single-, dual-, and triple-frequency GPS for varying time spans from 60 s down to 1 s. We\ndemonstrate, empirically as well as formally, that fast phase-only very-precise positioning is indeed\npossible, and we explain the circumstances that make this possible. The formal analyses are also\nperformed for a large area including Australia, a part of Asia, the Indian Ocean, and the Pacific\nOcean. We remark that in this contribution \"phase-only\" refers to phase-only measurements in the\nobservation model, while the code data are thus only used to compute the approximate values needed\nfor linearizing the observation equations....
Based on the Backward Four-Dimensional Variational Data Assimilation (Backward-4DVar) system with the Advanced Regional\nEta-coordinate Model (AREM), which is capable of assimilating radio occultation data, a heavy rainfall case study is performed\nusing GPS radio occultation (GPS RO) data and routine GTS data on July 5, 2007. The case study results indicate that the use of\nradio occultation data after quality control can improve the quality of the analysis to be similar to that of the observations and,\nthus, have a positive effect when improving 24-hour rainfall forecasts. Batch tests for 119 days from May to August during the\nflood season in 2009 show that only the use of GPS RO data can make positive improvements in both 24-hour and 48-hour\nregional rainfall forecasts and obtain a better B score for 24-hour forecasts and better TS score for 48-hour forecasts. When using\nradio occultation refractivity data and conventional radiosonde data, the results indicate that radio occultation refractivity data\ncan achieve a better performance for 48-hour forecasts of light rain and heavy rain....
Dual-frequency GNSS data processing is currently one of the most useful techniques for\nsounding the ionosphere. Hence, this work was aimed at the evaluation of ground-based GNSS data\nfor the continuous monitoring of polar patches in both hemispheres. In this contribution, we proposed\nto use epoch-wise relative STEC values in order to detect these structures. The applied indicator is\ndefined as a difference between an undifferenced geometry-free linear combination of GNSS signals\nand the background ionospheric variations, which were assessed with an iterative algorithm of\nfour-degree polynomial fitting. The occurrence of patches during the St. Patrick geomagnetic storm\nwas performed for validation purposes. The first part of the work confirmed the applicability of the\nrelative STEC values for such investigations. On the other hand, it also revealed the limitations related\nto the inhomogeneous distribution of stations, which may affect the results in both hemispheres. This\nwas confirmed with a preliminary cross-evaluation of GNSS and in situ SWARM datasets. Apart from\nthe periods with a well-established coincidence, the opposite situation, when both methods indicated\ndifferent parts of the polar ionosphere, was also observed. The second part of this contribution\ndepicted the feasibility of continuous patch detection for both regions, and thus the interhemispheric\ncomparison of the analyzed structures. It has demonstrated the strong disproportion between patches\nin the northern and southern hemispheres. This discrepancy seems to be related to the different\namount of plasma propagating from the dusk sector, which is justified by the values of relative\nSTEC at mid-latitudes. The observed structures are also strongly dependent on the orientation of the\ninterplanetary magnetic field....
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