Table of Content

25 October 2020, Volume 0 Issue 10

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Analysis of high-resolution X-band SAR data time-series coherence change of earth-rock dams

SHAN Qiang, JIANG Weiping, LI Tao, CHEN Lulu

2020, 0(10):  1-5.  doi:10.13474/j.cnki.11-2246.2020.0308

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This paper studies the effects of radar local incident angle and rainfall on coherence time-series variations of six small and medium dams in Gongming reservoir in Shenzhen, using 10 ascending and descending TerraSAR-X images with resolution of 1 m and rainfall data of the continuous weather stations near the dams. The experimental results show that both of coherence of concrete surface and grass surface decrease with the increase of local incident angle. Even though precipitation is relatively small, the average coherence of grass surface will decrease rapidly by approximately 0.1~0.2, and differential interference fringe will be less clear with more noise. Concrete surface is less sensitive to rainfall, while it still can become completely incoherent in case of heavy rainstorms. We concluded that in deformation monitoring of small and medium earth-rock dams, the slope and incident angle of the dams should be taken into account in order to select the optimal radar imaging parameter, and rainfall data should be used to evaluate the coherence of the surfaces and eliminate noise of interferogram.

Application of UAV photogrammetry technology in the emergency rescue of catastrophic geohazards

GUO Chen, XU Qiang, DONG Xiujun, JU Yuanzhen, NING Hao

2020, 0(10):  6-11,73.  doi:10.13474/j.cnki.11-2246.2020.0309

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Traditional geohazards emergency investigation is limited by the complex terrain, weather and other external conditions cannot obtain the detailed information of the hazards quickly and comprehensively, while UAV has the characteristics of strong flexibility, high timeliness and not affected by complex terrain, which has unique advantages in geohazards emergency investigation. Taking “6·24” Xinmocun landslide and “10·11” Baige landslide damming events as an example, this paper expounds the unmanned aerial vehicle (UAV) geohazards emergency investigation data acquisition and processing, mainly introduces the UAV three-dimensional digital terrain products in accurate description of geohazards, the application of the qualitative and quantitative analysis. Results show that the UAV photogrammetry technology provides a more scientific and efficient field image acquisition and remote sensing processing application solutions. It provides a technical and data support for the development of emergency rescue work smoothly and efficiently, and a scientific and effective way to guarantee the safety of site construction crews.

Feature point extraction of ridge line and valley line from DEM based on falling vector

HUANG Jiongyi, HUANG Peizhi, LI Jianqiang

2020, 0(10):  12-15.  doi:10.13474/j.cnki.11-2246.2020.0310

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In this paper, after studying the falling vector of terrain surface function, the falling vector characteristics of ridge point and valley point are derived by using the relevant mathematical principles according to the physical characteristics of the water separation of ridge line and confluence of valley line. A new method of extracting the feature points of ridge line and valley line based on falling vector is proposed after investigating into existing method. This method takes the minimum value of falling vector norm on the vertical section of falling vector as the criterion to determine the ridge point and valley point. The experiment shows that the selected points of ridge line and valley line extracted by this method are more accurate and reliable than the existing method.

Establishment of high-precision 3D calibration field based on baseline length method

MA Na, LIANG Jing, DONG Lan, WANG Xiaolong, LI Bo, MEN Lingling, LUO Tao

2020, 0(10):  16-20.  doi:10.13474/j.cnki.11-2246.2020.0311

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Since large-scale photogrammetry is calibrated with traditional measuring cameras, with limited accuracy, a high-precision, large-scale three-dimensional calibration field establishment method is proposed. This method uses natural marble with good stability as the basic structure, and designs a horn pedestal, uses micron-level multi-beam laser ranging to obtain the distance between two points, and then directly establishes a high-precision 3D calibration field based on the baseline adjustment model. The method is verified by simulating multiple sets of approximate coordinates and observations on distance. The results show that the simulation error of the approximate coordinates of the calibration field cannot exceed 3 mm, mean square of weight is equivalent to the simulation error of observation on the distance, and the standard deviation of the inversed value and the theoretical value of the distance is half of the simulation error of the observations on the distance, which verifies the correctness of calculation models and procedures. The calibration field can not only provide large-scale calibration for the measurement camera, but also perform irregular inspection on the measurement performance of the laser tracker.

Indentification of main and auxiliary roads at complex intersections under multiple feature constraints

ZHANG Honggang, LI Chengming, YU Meina, WU Pengda, GUO Man

2020, 0(10):  21-25,42.  doi:10.13474/j.cnki.11-2246.2020.0312

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Accurate identification of main roads and auxiliary roads is essential for the automatic synthesis of complex intersections. Traditional methods mostly rely on the straightness and curvature of road sections to describe the main roads and auxiliary roads at intersections. However, complex intersections have intricate structures and various morphological changes. Reliance on these two features for the identification of main and auxiliary roads is limited, and some forms Similar main branches cannot be identified. Therefore, this paper proposes a method for identifying main and auxiliary roads at complex intersections with multiple feature constraints. First extract feature points of complex intersections, interrupt arc segments based on feature points, identify parallel arc segments based on the straightness of the road segments, and then identify parallel clusters based on road ductility, angle, distance and other features to obtain complex intersections. Arterial roads, followed by identifying ramps on compactness and distance relationships to obtain auxiliary roads at complex intersections. Taking Nanjing OSM urban road network as an example, experiments show that the method in this paper can accurately identify the main road and auxiliary road sections of complex intersections, and the recognition accuracy is 93.60% and 89.43%, respectively.

Automatic extraction and reconstruction of powerlines from airborne LiDAR point clouds

ZHOU Qinkun, YUE Jianping, YANG Heng, ZHU Yimin

2020, 0(10):  26-30,37.  doi:10.13474/j.cnki.11-2246.2020.0313

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In order to realize more effective inspection of powerline corridor, this paper designs a method for automatic extraction and reconstruction of powerline from LiDAR point cloud data. The improved progressive morphology filtering is used to eliminate the ground point. It achieves rough extraction of powerline points through the segmentation based on the height difference threshold and elevation dispersion. The powerline linear model is obtained through RANSAC line inspection, relying on density detection, precise clustering of single powerline points is achieved. It complete the bundled conductors classification with the k-means algorithm. Finally, a least square fitting of the quadratic polynomial is performed to generate a powerline curve model. Experiments show that the correct rate of powerline point cloud extraction is over 98%, the false positive rate of non-powerline point cloud is as low as 1%, the fitting error of powerline linear model is below 5 cm and the curve model is below 3 cm. Fully meet the actual engineering needs.

DOM and DSM generation using airborne dual-antenna millimeter-wave InSAR in high mountain area of Sichuan

LI Yongjie, SUN Zhongchang, WEI Lideng, GAO Jian, YANG Honglei

2020, 0(10):  31-37.  doi:10.13474/j.cnki.11-2246.2020.0314

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The airborne dual-antenna millimeter-wave InSAR system is able to acquire DSM over difficult mountainous areas with steep or complicated topography efficiently and accurately for its flexible maneuverability, variable track, high coherence, high resolution, real-time acquisition, et al, which is one of the significant means for obtaining DSM. However, due to the large amount of airborne InSAR data, the current data processing capability and efficiency are relatively low. In response to these problems, the GPU parallel processing technology is adopted in this paper to carry out interference processing quickly and accurately, thus improving the efficiency of batch interference processing. The phase unwrapping is performed quickly based on the minimum balanced trees unwrapping algorithm. The SIFT algorithm is used to extract the tie points between adjacent images in the strip automatically and quickly, which improves the accuracy and efficiency of tie points selection.In this paper, 13 scenes of airborne InSAR data in the high mountainous area of Qionglai city, Sichuan province are taken as examples for analysis. The RMSE of the generated DOM and DSM in the three directions of X, Y and H are 1.839, 1.464 and 1.997 m respectively, which satisfies requirements of 1：5000 topographic mapping.

A normal distribution transform point cloud registration method based on BFGS correction

YUAN Zhicong, LU Tieding, LIU Rui

2020, 0(10):  38-42.  doi:10.13474/j.cnki.11-2246.2020.0315

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Point cloud registration is a key problem in point cloud data processing. For the problem of solving the Hessian matrix with high time complexity for the original normal distribution transformation algorithm, a modified normal distribution transform point cloud registration method based on the BFGS algorithm is proposed. The positive definite matrix is updated with the gradient value and incremental parameters of the objective function. The inverse matrix of the Hessian matrix is almost replaced by a positive definite matrix, which reduces the time complexity of the algorithm, ensures that the direction of each iteration of the algorithm is the direction where the function value drops in. The feasibility of this algorithm is verified by simulated data and measured data experiments. This algorithm improves the registration efficiency of the algorithm while maintaining the accuracy of the original normal distribution transformation algorithm.

Improvement of point cloud filtering algorithm for the progressive TIN

LING Xiaochun

2020, 0(10):  43-47.  doi:10.13474/j.cnki.11-2246.2020.0316

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This paper analyzes the defect that the feature points are easily misjudged as ground points in the process of Topcon LiDAR point cloud data processing by progressive TIN densification algorithm (PTD), proposes two kinds of improved methods. The first method is to use the local slope fitting method to improve the PDT algorithm, and sort the point cloud data according to the difference between the elevation value and the fitting elevation value solved by the fitting slope method from small to large, the point which is more greater possibility for the ground point is determined firstly, so as to obtain a more precise tin. The second method is to use thin plate spline(TPS) interpolation to improve the PTD algorithm, change the judgment parameter of candidate point in PTD to the threshold value of bending energy in TPS, so as to reduce misjudgment. The results show that considering the influence of the first error and the second error, the two improved algorithms are better than the traditional PTD algorithm in most terrain features, and have better filtering effect on low vegetation, bridges, slopes and other special objects.

The research of 3D mapping technology on oblique photogrammetric technique

ZHU Yiqun, WU Yuxin, JIN Guojian, LI Linqi

2020, 0(10):  48-52.  doi:10.13474/j.cnki.11-2246.2020.0317

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In recent years, with the rapid development of UAV technology, airborne positioning technology and image processing technology, tilt photogrammetry technology has been widely used in 1：1000 large-scale topographic mapping. However, due to various technical limitations, ordinary UAV aerial photogrammetry can not meet 1：500 large-scale topographic mapping. Based on this, this paper studies tilt photogrammetry in three aspects: image control density, model resolution and mapping method, and proposes a tilt mapping method fitting for 1：500 scale topographic map of cities and towns. The large-scale topographic map of Wencheng county obtained from the evaluation test shows that the plane accuracy of the result can reach 0.059 m, the elevation accuracy can reach 0.064 m, and the accuracy is in good condition, which play a certain guiding role in the future when taking this method for surveying and mapping.

An improved one-dimensional maximum entropy star image segmentation algorithm

ZHANG Geng, ZHANG Chao, MI Kefeng, ZHAN Yinhu, LI Chonghui

2020, 0(10):  53-57.  doi:10.13474/j.cnki.11-2246.2020.0318

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In CCD astronomical measurement technology, the accuracy of star point centroid coordinate extraction directly affects the coordinate precision of field astronomical measurement, and star image segmentation algorithm is the most critical part of digital star image processing technology. The one-dimensional maximum entropy star image segmentation algorithm has a very good binarization effect, and can fully retain the information of star image, and its reliability and accuracy have been experimentally verified. Based on the one-dimensional maximum entropy star image segmentation algorithm, this paper proposes an improved star point region partitioning algorithm, which can greatly improve the computational efficiency of the one-dimensional maximum entropy algorithm without reducing the accuracy and reliability, and improve the efficiency of field astronomical measurement operations. The availability of astronomical measurement operations has better applicability in practical operations.

Research on fractal features of multipath effect for pseudolite and its elimination strategy

SANG Wengang, HUANG Liming, ZHAO Peihua, LIU Yingchun, LU Kai

2020, 0(10):  58-62.  doi:10.13474/j.cnki.11-2246.2020.0319

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The multipath effect is of major concern in pseudolite precise applications. This paper first validate the multipath has the features of fractal and then study the difference on the modulus maximum between fractal and Gauss noise by wavelet transform. A new method is proposed to separate multipath and noise base on fractal theory and wavelet transform for stationary applications. The filed tests show this method can effectively reduce the multipath effect of pseudolite and improve the accuracy and reliability of pseudolite augmented GPS positioning system. This method is just based on the fractal of the signal without introducing extra priori information and more suitable for some harsh observation conditions, especially for deformation monitoring applications.

Precision analysis and control method of inverse calculation of plane four parameter

WANG Youkun, YU Zhangrong, ZHANG Junhua, SHI Shengchun

2020, 0(10):  63-67.  doi:10.13474/j.cnki.11-2246.2020.0320

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Planar four-parameter coordinate transformation model has the advantages of convenient calculation and high precision. It has been widely used in the transformation of different planar coordinate systems. A lot of research work has been done to improve the accuracy and applicability of the model, while ignore the impact of high-precision conversion results on parameter confidentiality. It is necessary to analyze the precision and control method of parameter inversion in order to meet the requirement of conversion parameter confidentiality. Firstly, the internal coincidence error and extrapolation error of the transformation model are deduced. Then, the coordinate results are transformed by the original conversion parameter without error and with error respectively, and different coordinate errors are added to the transformed results. Finally, different coordinate points with different distribution and number are selected to participate in the conversion parameter inversion, so as to analyze the accuracy of the parameters inversion of different schemes. The experimental results show that the accuracy of parameter inversion can be continuously improved by increasing the number of conversion points and expanding the conversion range, but the accuracy is as the same as the original conversion parameter achieved. Therefore, the effective way of parameter confidentiality firstly needs to reduce the accuracy of the original conversion parameter, and then add different errors to the coordinate results according to the distribution range, quantity and accuracy application requirements of the converted results, so as to achieve the effect of parameter confidentiality.

Analysis of the effect of antenna phase center correction on the precise positioning of BDS second-generation satellite

WANG Na, DUAN Longfei, XU Weidong, WANG Zhiyi

2020, 0(10):  68-73.  doi:10.13474/j.cnki.11-2246.2020.0321

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Accurate correction of the deviation of PCO/ PCV for the satellite end is an important prerequisite to realize the precise point positioning (PPP). In this paper, the evaluation of the BDS-Ⅱ PPP accuracy is conducted based on different PCO/ PCV correction value and precise orbit and clock of different IGS analysis center. In the process of evaluation, 15 MGEX stations are selected, and four sets of schemes are designed to deal with static PPP and dynamic PPP respectively. The results show that: ①the maximum error caused by the PCV in the line of sight for three different types of BDS satellite can reach 10 cm, which must be corrected. ②when the precision product and PCO/PCV correction value of the same analysis center are used, the coordinate residual error is small, the convergence speed is faster, and the convergent N, E, U is higher in three directions. ③When the precise orbit and the clock difference of the ESA are used for PPP solving, the dynamic positioning residual RMS on the whole is the lowest, and the dynamic positioning effect is preferable, and the rate of improvement in the E, N, U direction is about 31%, 20% and 9% relative to the use of IGS-based PCO/ PCV. This paper has certain reference value for the parameter model selection of high precision dynamic and static navigation and positioning.

The application of improved CIR algorithm in solving BDS long baseline ambiguity

LIU Wei, LIU Guochao, ZHENG Xiaozhan, ZHANG Qinghua

2020, 0(10):  74-78.  doi:10.13474/j.cnki.11-2246.2020.0322

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Under the condition of long baseline, the ionospheric delay and tropospheric delay cannot eliminate well due to the weak spatial correlation between stations, which cause the success rate of CIR method in solving ambiguity under long baseline condition is low. This paper selects the combination of long wavelength and weak ionosphere to improve the combination coefficient of wide lane, uses the combination (-1, -5, 6) instead of the traditional wide lane combination(0, -1, 1), and the weak ionosphere geometric phase combination (4, -5, 2) instead of the traditional narrow lane combination (0, 0, 1), adopts the linear combination of the multi frequency pseudorange observations and the wide lane phase observations to eliminate the first order term of ionospheric delay. Through the analysis of measured data, the algorithm proposed in this paper can effectively solve the fuzzy degree of ultra-wide lane and wide lane, and improve the success rate of ambiguity resolution.

Land-sea transition zone topographic mapping fusing new multi-technology

DING Shijun, ZHU Mingran

2020, 0(10):  79-84.  doi:10.13474/j.cnki.11-2246.2020.0323

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In this paper, a new type of high-precision, seamless land sea integrated measurement system is discussed. Based on the post-processing differential integrated navigation technology, taking customized eight wheeled vehicle and paddy field vehicle as platform, the system integrates infrared laser scanning technology, towed measurement technology, single beam sounding technology and other surveying and mapping means to ensure the accuracy and coverage of the mapping results. The results of application show that the system has the characteristics of high integration, high data acquisition accuracy, high data collection efficiency, and easy equipment operation. The system can provide reference for surveying and mapping of large land sea transitional zone, including shallow sea, silt beach, bedrock beach, sandy beach, etc.

Research on the rapid practical modeling technology of ground-to-air integration

HAN Youmei, XU Mengbing, HU Zhongxiang, WANG Shuai

2020, 0(10):  85-88.  doi:10.13474/j.cnki.11-2246.2020.0324

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The development of intelligent surveying and mapping geographic information service puts forward higher requirements on the realism, practicability and precision of the real-life 3D model. How to quickly produce high-definition and high-precision real-world 3D models has become one of the research directions of surveying and mapping geographic information hotspots. With the characteristics of current aerial tilt photogrammetry modeling, this paper explores the technology of integrated modeling based on aerial tilt photography and ground close-range photogrammetry. It studies a set of ground and air integration from three aspects: close-range sensor design, data acquisition and data processing. The modeling process and the ground-space integrated real-world model of the experimental area is completed, and good results are obtained. This research makes up for the lack of deformation or even the lack of aerial tilt photography modeling in the near-surface model, and makes the real-time modeling based on tilt photogrammetry into a new stage.

Coastline extraction of remote sensing image by combining Otsu, regional growth method with morphology

ZHANG Jin, LAI Zulong, SUN Jie

2020, 0(10):  89-92.  doi:10.13474/j.cnki.11-2246.2020.0325

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Aiming at the low accuracy of the existing coastline extraction methods, which cannot meet the needs of processing various sensor satellite images and the extraction of linear and complex coastlines. This paper proposes a combination of Otsu, regional growth method with morphology method for coastline extraction of remote sensing images. And the experiments show that this coastline extraction method can give full play to the advantages of Otsu, regional growth method and morphology separately in the extraction of coastline, which improves the accuracy of coastline extraction greatly. Two different satellite image data are used to test to verify the good applicability of the method under different conditions.

Remote sensing landform recognition algorithm based on improved attention mechanism

ZHANG Zhentong, SHAN Yugang, YUAN Jie

2020, 0(10):  93-96,100.  doi:10.13474/j.cnki.11-2246.2020.0326

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Recognizing remote sensing landforms has been a research hotspot in the field of remote sensing image applications in recent years. Using deep learning algorithms to identify remote sensing images has higher accuracy and robustness than traditional methods. Aimed at the problems of high target complexity and feature information in remote sensing images. This paper proposes a remote sensing image recognition algorithm based on an improved attention mechanism. A parallel attention mechanism (CS) and neural network model are combined to improve training with weakly supervised learning. At the same time, a double loss function is used to alleviate the problem of data overfitting. The experimental results show that the total accuracy of the model in this paper is 98.35%, and the Kappa coefficient is 0.95, which is better than other deep learning algorithms and can effectively recognize natural landforms.

Method of building extraction from UAV oblique photography point cloud based on cloth simulation

WANG Guo, WANG Qiang, LIU Shaotang, YANG Fuqin, ZHAO Guangxing, YANG Bin

2020, 0(10):  97-100.  doi:10.13474/j.cnki.11-2246.2020.0327

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Inspired by the idea of cloth simulation filtering, this paper presents a new method of building extraction from dense matching point cloud based on UAV oblique photography. The method introduces cloth simulation to identify the top of the building as the first step. By simulating the falling process of cloth, the function between cloth and corresponding dense matching point cloud is analyzed, and the position where cloth stays after gravity falling is determined as the building top. And then buildings are distinguished by the density clustering algorithm so as to realize the monomer extraction of the building top surface. The experimental results show that the method can achieve better results and provide a new idea for building extraction from dense matching point cloud based on UAV oblique photography.

Accuracy evaluation and application of urban coordinate system based on LiDAR

HU Yaofeng, HU Xinran

2020, 0(10):  101-105.  doi:10.13474/j.cnki.11-2246.2020.0328

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Taking Guangzhou as an example, this paper expounds the traditional method of Gauss projection deformation. Combined with Guangzhou high-precision LiDAR and construction project with Guangzhou 2000 coordinate system, this paper introduces high-precision LiDAR data acquisition and DEM production process, designs two key technical methods of data processing of Gauss projection composite deformation, develops the automatic processing software and puts forward a new method of urban coordinate system accuracy evaluation.

Application of UAV tilt photogrammetry in 3D reconstruction of overpass

YU Jiankang

2020, 0(10):  106-109.  doi:10.13474/j.cnki.11-2246.2020.0329

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This paper introduces the UAV tilt photogrammetry technology and its key technologies. Firstly, the high repetition rate oblique image of an overpass is collected through the designed UAV route. Secondly, the processing flow of the collected image data is described in detail, and the technical process of using the collected image data for the 3D modeling of the overpass is also described in detail. Finally, the 3D measurable model of the overpass scene is established. By comparing the accuracy of the selected real site coordinates with the corresponding point coordinates on the bridge model, the results show that the accuracy of the real 3D scene model is reliable, which is made by the inclined image collected by UAV, and the plane and elevation accuracy meet the requirements of the specification, which can be applied to the practical engineering of overpass and other buildings.

An automatic change detection method of surface coverage based on joint features

KONG Hui, JIN Hongfang

2020, 0(10):  110-113,122.  doi:10.13474/j.cnki.11-2246.2020.0330

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Efficient change detection method of land cover has important significance in geographical conditions monitoring. In view of the low efficiency of manual visual interpretation and the high error rate and omission rate of software automatic interpretation in current land cover detection, an automatic change detection method of land cover types based on union feature is proposed in this study. Through the comparison of seven different feature combination schemes, the optimal combination form of combination gray co-occurrence matrix, gray histogram, spectral statistical characteristics and object characteristics is established. Besides, support vector machine high-dimensional classifier is designed for classification. The experiment results show that, in the case of complex land cover distribution in Zhejiang province, the accuracy of this method is more than 85% in detecting the type change of artificial structures such as building areas and construction sites, based on the domestic high-resolution satellite images with resolution better than 1 m. Change detection of grassland and cultivated land can also achieve good results.

Research on GNSS-MR tide level monitoring based on EMD

WANG Ruifang

2020, 0(10):  114-117.  doi:10.13474/j.cnki.11-2246.2020.0331

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As a new method of remote sensing, GNSS-MR can detect the surface environment with multipath effect. This method has been applied to tidal level detection and has achieved good results. Aiming at the signal mixing problem of this method, this paper proposes to use empirical mode decomposition to extract the seawater signal of the signal-to-noise ratio to avoid the influence of noise signal and coastal reflection signal. Taking the SC02 station, located in Friday Harbor, Washington, USA, as an example, the tidal level data obtained by inversion using EMD and traditional methods are compared and analyzed. The research results show that this method improves the RMSE of LSP results by 5.36% compared with the traditional methods, and proves that the method can be used to extract relatively pure signals of the sea surface and improve the inversion accuracy to a certain extent.

Multiple encrypted grid interpolation coordinate transformation

LI Wangmin, LI Xiulong, WANG Dongge, MA Defu, CHEN Wenxiang, LIU Yanan

2020, 0(10):  118-122.  doi:10.13474/j.cnki.11-2246.2020.0332

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After implementing CGCS2000 in China, massive amounts of surveying and mapping data in multi-coordinate-system and multi-format need to be coordinate transformed in many places. In practice, the top secret transformation parameters bring great difficulties to the practical application, which among geodetic coordinate systems, ellipse-centered coordinate systems and the local independent coordinate systems. Considering the security and consistency of the parameter coordinate transformation, a multiple encrypted grid interpolation coordinate transformation method is proposed in the paper, and developed into the coordinate transformation software based on two and three dimensional grid data. The method has also been applied into the ZHBDCORS. Actual verification shows that the method has the high safety and practicability.

Study on surface settlement of Golmud city based on time series InSAR

DOU Chao, ZHAO Lijiang, ZHANG Shengpeng, LIU Yuxin, MA Guobao

2020, 0(10):  123-126.  doi:10.13474/j.cnki.11-2246.2020.0333

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InSAR and related technologies have some advantages in urban land settlement monitoring. This paper uses the 37-sentiment Sentinel-1 satellite SAR image data from December 4, 2015 to January 10, 2018, based on InSAR time series analysis technology to monitor the surface deformation of the urban area and its surroundings in Golmud.The results show that 252 889 coherent points are extracted based on coherence and other indicators, with an average of 501 coherent points per square kilometer, after the mask removes the larger error points, 252 035 coherent points are actually used; the overall sedimentation rate of Golmud city and its surrounding suburbs is within 5 mm/a, no obvious subsidence area is found or large-scale settlement belt, the sedimentation rate in the southern part of the urban area is lower than that in the north.

Integration technology of 3DGIS and BIM and its application in highway tunnel intelligent management and maintenance system

SUN Yumei, LI Yong, NIE Zhengang

2020, 0(10):  127-130.  doi:10.13474/j.cnki.11-2246.2020.0334

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With the rapid growth of highway in China, highway tunnel operation and maintenance problems are increasingly prominent. In order to solve the problems that the complex structure, numerous equipment, poor information sharing and difficult patrol inspection of the highway tunnel, the integration technology of 3DGIS and BIM is applied to the management and maintenance of highway tunnel. Making full use of the respective advantages of GIS and BIM, the micro data of all kinds of BIM building models are integrated into the macro geographical environment established by 3DGIS, which form a three-dimensional integrated visual full information model of tunnel space and surrounding geographical environment. It realizes the intelligent management and maintenance functions such as tunnel information monitoring, health detection, application management and safety warning, and improves the management level of highway tunnel maintenance refinement.

Analysis of geospatial grid coding technology

WANG Li, WU Wei, DENG Guoqing, TONG Xiaochong, LI Junfeng

2020, 0(10):  131-134,147.  doi:10.13474/j.cnki.11-2246.2020.0335

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The geospatial grid divides the geospatial region into spatial reference systems with different scale grid units. Grid coding uses the structured index technology of location to assign identifier to each grid of geospatial grid system, so as to realize the unified identification of grid location. This paper contrasts the identification requirements of the multi-level and multi-resolution global mesh grid system formed by nesting and sectioning according to the uniform rules,based on the analysis of the current geospatial index identification technology, discusses the coding scheme of the global mesh grid system, and proposes a set of geospatial grid identification system which realize the unique identification of the global grid units, describes the spatial position of grid cells,and reflects the spatial relationship between grid cells.

Construction model and research on application of spatio-temporal big data service platform: taking Chongqing as an example

CAO Chunhua, ZHANG Zelie, CHENG Yuxiang, YUAN Chao, LIANG Xing

2020, 0(10):  135-138,156.  doi:10.13474/j.cnki.11-2246.2020.0336

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In recent years, China has vigorously developed the digital economy. As a key foundation for the development of digital economy, spatio-temporal big data has raised higher requirements for data aggregation, timely updating, intelligent processing, high-performance services and supporting multi-type applications in its application service process. This paper proposes the construction mode method and technical thinking of spatio-temporal big data platform around building spatio-temporal big data resources, realizes the intelligent processing of spatio-temporal big data, provides spatio-temporal big data services, and explores the construction mode of spatio-temporal big data application combined with the already developed wisdom applications.

A method of floating car data correction based on OSM

HU Xiangyong, GUO Yuan

2020, 0(10):  139-142,163.  doi:10.13474/j.cnki.11-2246.2020.0337

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Floating car track data has great significance for the production and update of road map because of the wide coverage area, low cost and the short update cycle. However, compared to other data sources, the accuracy of it is low. This article adopts the OSM as reference data to correct the floating car track data. Firstly, the floating cat track data is matched with the OSM through a hierarchical space-time map matching algorithm. Then, an attraction model is used to correct the data. Finally, the taxs track data of Wuhan is used to verify the effectiveness of the algorithm. The result shows that the method in this paper could improve precision of floating car truck data.

The efficiency improvement of spatial data analysis by using the distributed automatic parallel processing framework

LIANG Zheheng, WU Baoyou, XIE Gangsheng

2020, 0(10):  143-147.  doi:10.13474/j.cnki.11-2246.2020.0338

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Focusing on the efficiency improvement of GIS application system in spatial data analysis, in view of the problem of data analysis and processing efficiency, this paper puts forward a set of efficiency improvement method based on distributed automatic parallel processing framework. It expounds how to realize the distributed automatic parallel processing based on the key technologies such as ArcPy, WebAPI, distributed scheduling and scheduling control factors. It is helpful to solve the efficiency problem of large amount of spatial data analysis and processing conveniently and efficiently.

Key points of national security prevention and control of high precision map

ZHANG Yuxin, ZUO Dong

2020, 0(10):  148-151.  doi:10.13474/j.cnki.11-2246.2020.0339

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In recent years, the automotive industry has gone into the era of intelligence, self-driving cars will surely lead the zeitgeist, the following is the development of high-precision map industry. However, due to the emergence of high-precision maps, the way of reading navigation electronic map has changed from human reading to machine reading. Accompanying changes in data collection, update, use and other aspects, as well as possible problems can’t be ignored. Particularly, some links will threaten national security if mishandled. This paper will begin with the risk points that high-precision map may harm to national security, analyze the national security risks of high-precision map in data collection, update and use, formulate prevention and control points, and play a corresponding role in promoting the healthy development of high precision map industry.

Research on zero-watermark of electric navigational chart for tampering localization

CHEN Yang, PENG Rencan, DONG Jian, LI Binbin, TANG Lulu

2020, 0(10):  152-156.  doi:10.13474/j.cnki.11-2246.2020.0340

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In view of the data security problems in the application of ENC, combined with the integrity certification requirements of CRC checksums under S-57 standard, a zero watermark algorithm for ENC is proposed which takes into account the characteristics of point tampering. Based on the analysis of the distribution law of the discrete point coordinate data represented by longitude and latitude in the ENC object standard (element), the algorithm constructs the generation model of the longitude-latitude check code, and combines the number of the discrete point to carry out the binary tree block processing of the ENC cell network, and solves the binary sequence based on the longitude-latitude check code of the discrete point by block column and scrambled encrypted watermark image are XOR operation to construct zero watermark image. In the algorithm, the introduction of the grid block technology and longitude-latitude check code can ensure the accuracy of ENC data and meet the CRC check sum, and it has the characteristics of point tampering location. Experimental results show that the watermark algorithm has good robustness, invisibility and a certain degree of tampering positioning accuracy, which is suitable for copyright protection of ENC.

Research on ground uplift using two time series InSAR technologies

ZHANG Yuntao, WANG Hongchang, WANG Xintian, WANG Bo, LIANG Fei

2020, 0(10):  157-159,163.  doi:10.13474/j.cnki.11-2246.2020.0341

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In recent years, the government has attached great importance to the monitoring and management of ground subsidence, but little research has been done on the phenomenon and mechanism of ground uplift. In this paper, PS-InSAR and NSBAS are used to monitor the ground deformation in Zibo with Sentinel-1 ascending and descending orbit data. It analyzes the consistency of lifting in the area with coal mining conditions through the date.

Application of Leica LiDAR technology in the whole lifecycle of railway

LI Hailiang

2020, 0(10):  160-163.  doi:10.13474/j.cnki.11-2246.2020.0342

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In order to apply LiDAR technology to the whole lifecycle of railway, give full play to the advantages of laser radar technology, taking Leica Inc related laser radar products as an example, the characteristics of different types of laser radar and the measurement requirements of different stages of railway engineering are analyzed systematically, and the application methods of laser technology in the whole life cycle of railway are summarized. The analysis of typical engineering applications shows that LiDAR technology can significantly improve the efficiency and quality of railway engineering survey, and has good application prospects.

Evaluation and analysis of measurement accuracy of terrestrial 3D laser scanner

LIU Shengnan, TAO Jun

2020, 0(10):  164-166.  doi:10.13474/j.cnki.11-2246.2020.0343

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In view of the accuracy evaluation of the ground 3D laser scanner used in the deformation monitoring of urban rail transit, this paper mainly describes the three error sources of 3D laser scanner: itself, external environment and scanned targets. We analyzes the error of ranging and angle measurement of 3D laser scanner and verifies the feasibility of 3D laser scanning technology used in rail transit deformation monitoring through experiments.