THE PERFORMANCE OF BDS RELATIVE POSITIONING USAGE WITH REAL OBSERVATION DATA

With the first phase of COMPASS/BeiDou-2 (BDS) completed, the assessment ofpositioning performance and the characterization of its system are analyzed andpresented. Pseudo-range and carrier phase measurements modulated on B1 and B2have been collected in Shanghai, from 00:00 to 24:00 on 28 December, 2012.Compared with GPS, visibility and measurement quality of BDS’s GEO, IGSO andMEO satellites are analyzed. DOP during the whole orbital period is also analyzedthe results demonstrate that BDS’s HDOP is better than GPS’s one, but VDOPopposite. Furthermore, the result of positioning is also presented and analyzed.Short baselines are estimated by standalone BDS and GPS’s carrier phasemeasurement, respectively, using 48 segmentations of observations during a wholeday (24 hours, each segmentation, is about 30 minutes observation). The analysis ofstatic relative positioning demonstrates that BDS could achieve to millimeter level,corresponding to GPS. Kinematic result is produced by double differenced carrierphase observations with the ambiguities fixed under the constraint of precise shortbaseline.The result shows that the centimeter accuracy could be achieved. Whencomparing the results of kinematic baseline solutions, performance of BDS is worsethan GPS on North and Up components, but oppositely on the component of East inthe kinematic baseline processing

Water Resources Carrying Capacity Forecast of Jining Based on Non-Linear Dynamics Model

AbstractIn order to alleviate the problem of water resources shortage of Jining City, make reasonable use of water resources,and improve the water resources capacity of Jining City, the methods of the water resources capacity are researched.The system dynamics method is choosed to forecast the Water Resources Carrying Capacity (WRCC) of Jining City in the next 20 years. Three plans are taken, and the predicted results are analyzed. It has a certain significance to practice

Validation of 7 Years in-Flight HY-2A Calibration Microwave Radiometer Products Using Numerical Weather Model and Radiosondes

Haiyang-2A (HY-2A) has been working in-flight for over seven years, and the accuracy of HY-2A calibration microwave radiometer (CMR) data is extremely important for the wet troposphere delay correction (WTC) in sea surface height (SSH) determination. We present a comprehensive evaluation of the HY-2A CMR observation using the numerical weather model (NWM) for all the data available period from October 2011 to February 2018, including the WTC and the precipitable water vapor (PWV). The ERA(ECMWF Re-Analysis)-Interim products from European Centre for Medium-Range Weather Forecasts (ECMWF) are used for the validation of HY-2A WTC and PWV products. In general, a global agreement of root-mean-square (RMS) of 2.3 cm in WTC and 3.6 mm in PWV are demonstrated between HY-2A observation and ERA-Interim products. Systematic biases are revealed where before 2014 there was a positive WTC/PWV bias and after that, a negative one. Spatially, HY-2A CMR products show a larger bias in polar regions compared with mid-latitude regions and tropical regions and agree better in the Antarctic than in the Arctic with NWM. Moreover, HY-2A CMR products have larger biases in the coastal area, which are all caused by the brightness temperature (TB) contamination from land or sea ice. Temporally, the WTC/PWV biases increase from October 2011 to March 2014 with a systematic bias over 1 cm in WTC and 2 mm in PWV, and the maximum RMS values of 4.62 cm in WTC and 7.61 mm in PWV occur in August 2013, which is because of the unsuitable retrieval coefficients and systematic TB measurements biases from 37 GHz band. After April 2014, the TB bias is corrected, HY-2A CMR products agree very well with NWM from April 2014 to May 2017 with the average RMS of 1.68 cm in WTC and 2.65 mm in PWV. However, since June 2017, TB measurements from the 18.7 GHz band become unstable, which led to the huge differences between HY-2A CMR products and the NWM with an average RMS of 2.62 cm in WTC and 4.33 mm in PWV. HY-2A CMR shows high accuracy when three bands work normally and further calibration for HY-2A CMR is in urgent need. Furtherly, 137 global coastal radiosonde stations were used to validate HY-2A CMR. The validation based on radiosonde data shows the same variation trend in time of HY-2A CMR compared to the results from ECMWF, which verifies the results from ECMWF

High-order Spatial Interactions Enhanced Lightweight Model for Optical Remote Sensing Image-based Small Ship Detection

Accurate and reliable optical remote sensing image-based small-ship detection is crucial for maritime surveillance systems, but existing methods often struggle with balancing detection performance and computational complexity. In this paper, we propose a novel lightweight framework called \textit{HSI-ShipDetectionNet} that is based on high-order spatial interactions and is suitable for deployment on resource-limited platforms, such as satellites and unmanned aerial vehicles. HSI-ShipDetectionNet includes a prediction branch specifically for tiny ships and a lightweight hybrid attention block for reduced complexity. Additionally, the use of a high-order spatial interactions module improves advanced feature understanding and modeling ability. Our model is evaluated using the public Kaggle marine ship detection dataset and compared with multiple state-of-the-art models including small object detection models, lightweight detection models, and ship detection models. The results show that HSI-ShipDetectionNet outperforms the other models in terms of recall, and mean average precision (mAP) while being lightweight and suitable for deployment on resource-limited platforms

Coastal Aquaculture Extraction Using GF-3 Fully Polarimetric SAR Imagery: A Framework Integrating UNet++ with Marker-Controlled Watershed Segmentation

Coastal aquaculture monitoring is vital for sustainable offshore aquaculture management. However, the dense distribution and various sizes of aquacultures make it challenging to accurately extract the boundaries of aquaculture ponds. In this study, we develop a novel combined framework that integrates UNet++ with a marker-controlled watershed segmentation strategy to facilitate aquaculture boundary extraction from fully polarimetric GaoFen-3 SAR imagery. First, four polarimetric decomposition algorithms were applied to extract 13 polarimetric scattering features. Together with the nine other polarisation and texture features, a total of 22 polarimetric features were then extracted, among which four were optimised according to the separability index. Subsequently, to reduce the “adhesion” phenomenon and separate adjacent and even adhering ponds into individual aquaculture units, two UNet++ subnetworks were utilised to construct the marker and foreground functions, the results of which were then used in the marker-controlled watershed algorithm to obtain refined aquaculture results. A multiclass segmentation strategy that divides the intermediate markers into three categories (aquaculture, background and dikes) was applied to the marker function. In addition, a boundary patch refinement postprocessing strategy was applied to the two subnetworks to extract and repair the complex/error-prone boundaries of the aquaculture ponds, followed by a morphological operation that was conducted for label augmentation. An experimental investigation performed to extract individual aquacultures in the Yancheng Coastal Wetlands indicated that the crucial features for aquacultures are Shannon entropy (SE), the intensity component of SE (SE_I) and the corresponding mean texture features (Mean_SE and Mean_SE_I). When the optimal features were introduced, our proposed method performed better than standard UNet++ in aquaculture extraction, achieving improvements of 1.8%, 3.2%, 21.7% and 12.1% in F1, IoU, MR and insF1, respectively. The experimental results indicate that the proposed method can handle the adhesion of both adjacent objects and unclear boundaries effectively and capture clear and refined aquaculture boundaries

Composite metamaterials with dual-band magnetic resonances in the terahertz frequency regime

Composite metamaterials(CMMs) combining a subwavelength metallic hole array (i.e. one-layer fishnet structure) and an array of split-ring resonators(SRRs) on the same board are fabricated with gold films on silicon wafer. Transmission measurements of the CMMs in the terahertz range have been performed. Dual-band magnetic resonances, namely, a LC resonance at 4.40 THz and an additional magnetic resonance at 8.64 THz originating from the antiparallel current in wire pairs in the CMMs are observed when the electrical field polarization of the incident light is parallel to the gap of the component SRR. The numerical simulations agree well with the experimental results and further clarify the nature of the dual-band magnetic resonances.Comment: 4 figures, 14 page

The complete mitochondrial genome of the wallaroo (Macropus robustus) and the phylogenetic relationship among

ABSTRACT The complete mitochondrial DNA (mtDNA) (16,896 nt) of the wallaroo (Macropus robustus) was sequenced. The concatenated amino acid sequences of 12 mitochondrial protein-coding genes of the wallaroo plus those of a number of other mammals were included in a phylogenetic study of early mammalian divergences. The analysis joined monotremes and marsupials (the Marsupionta hypothesis) to the exclusion of eutherians. The analysis rejected significantly the commonly acknowledged Theria hypothesis, according to which Marsupialia and Eutheria are grouped together to the exclusion of Monotremata. The region harboring the gene for lysine tRNA (tRNA-Lys) in the mtDNA of other vertebrates is in the wallaroo occupied by a sequence (tRNA-Lys) that lacks both an anticodon loop as well as the anticodon for the amino acid lysine. An alternative tRNA-Lys gene was not identified in any other region of the mtDNA of the wallaroo, suggesting that a tRNA-Lys of nuclear origin is imported into marsupial mitochondria. Previously described RNA editing of tRNA-Asp and rearrangement of some tRNA genes were reconfirmed in the mtDNA of the wallaroo. The divergence between Monotremata͞Marsupialia and Eutheria was timed to Ϸ130 million years before present (MYBP). The same calculations suggested that Monotremata and Marsupialia diverged Ϸ115 MYBP and that Australian and American marsupials separated Ϸ75 MYBP. The findings also show that many, probably most, extant eutherian orders had their origin in middle to late Cretaceous times, 115-65 MYBP

Surface plasmon polaritons assisted diffraction in periodic subwavelength holes of metal films with reduced interplane coupling

Metal films grown on Si wafer perforated with a periodic array of subwavelength holes have been fabricated and anomalous enhanced transmission in the mid-infrared regime has been observed. High order transmission peaks up to Si(2,2) are clearly revealed due to the large dielectric constant contrast of the dielectrics at the opposite interfaces. Si(1,1) peak splits at oblique incidence both in TE and TM polarization, which confirms that anomalous enhanced transmission is a surface plasmon polaritons (SPPs) assisted diffraction phenomenon. Theoretical transmission spectra agree excellently with the experimental results and confirm the role of SPPs diffraction by the lattice.Comment: 4 pages, 5 figures, 26 reference