Acta Geodaetica et Cartographica Sinica

Ridge estimation algorithm to ill-posed uncertainty adjustment model

LU Tieding, WU Guangming, ZHOU Shijian

2019, 48(4): 403-411. doi:10.11947/j.AGCS.2019.20180044

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Uncertainties usually exist in the process of acquisition of measurement data, which affects the parameter estimation results. The solution method of uncertainty adjustment model can effectively improve the validity and reliability of parameter estimation. When the coefficient matrix of the observation equation has a singular value close to zero, the ridge estimation can effectively suppress the influence of the ill-posed state of the observation equation on the parameter estimation results.When the uncertainty adjustment model is ill-posed, it is more seriously affected by the error of the coefficient matrix and the observation,this paper applies ridge estimation method to ill-posed uncertainty adjustment model, derives an iterative algorithm to improve the stability and reliability of the result, and verifies it with two examples. The results show that the new method is effective and feasible.

Bias-corrected variance components estimation of Partial EIV model

WANG Leyang, WEN Guisen

2019, 48(4): 412-421. doi:10.11947/j.AGCS.2019.20170693

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Considering the methods of variance components estimation (VCE) in Partial errors-in-variables (Partial EIV) model have not considered the effect of the bias of parameter estimates, the formulas of bias and second-order covariance matrix of parameter estimates are presented with the Partial EIV model regarded as a non-linear function and the parameter estimates after bias-correct are calculated. Combining the VCE method, the matrix variable influenced by the parameter estimates is updated, and an iterative method of variance components estimation based on bias-correct is given. The experiments show that the reasonable parameter estimates and its second-order approximate covariance results are affected by the bias of parameter estimates. The reasonable parameter estimates and variance components estimates can be obtained through the bias-correct and the second-order information obtained can reasonably evaluate precision of parameter estimates.

Infinite expansions of the auxiliary latitudes with respect to the geodetic latitude

CHEN Cheng, JIN Lixin, BIAN Shaofeng, LI Songlin

2019, 48(4): 422-430. doi:10.11947/j.AGCS.2019.20170747

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By using the theory of infinite series and the Lagrange inversion theorem, the infinite expansions of the auxiliary latitudes in geodesy and cartography with respect to the geodetic latitude are given, which are the power series of the first eccentricity of the reference ellipsoid. The inverse solutions of the isometric and the conformal latitudes can be obtained from the recurrences of a number of known coefficients. The forward expansion of the conformal latitude is proposed on the basis of the Taylor expansion of the Gudermannian function, and the forward expansion of the rectifying latitude is given in which the coefficient can be expressed as a explicit determinant by the division of power series. Compared the coefficients of the auxiliary latitudes expansions at order e⁰ to e⁴⁰ with the results by the computer algebra system Mathematica and the corresponding cost time, the algorithm of this paper is verified to be correct and fast. By taking CGCS2000 reference ellipsoid, the numerical experiment is made for the expansions and then the correctness is further proved.

Parameter method data processing for CPⅢ precise trigonometric leveling network

LI Jianzhang, YAN Haowen

2019, 48(4): 431-438. doi:10.11947/j.AGCS.2019.20180265

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In view of the limitation of the difference method, a parameter CPⅢ adjustment method is proposed for precision trigonometric elevation network. The result proves that the proposed method, being simple, efficient and time-saving, avoids the negative influences caused by the correlation among the data acquired from the difference method, and thus improves the accuracy. In addition, the study is conducted about strict weight of the CPⅢ precision trigonometric elevation network. The result shows that when the vertical angle is smaller than 3°, the ranging error of trigonometric leveling can be dismissed, and the accuracy of CPⅢ precision triangulation elevation control network does not change significantly before and after strict weight determination.

Probabilistic water body mapping of GF-3 images based on prior probability estimation

MENG Lingkui, MAO Xudong, WEI Zushuai, ZHANG Wen

2019, 48(4): 439-447. doi:10.11947/j.AGCS.2019.20170732

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We combine k-means cluster algorithm with the statistical model of SAR(synthetic aperture radar) images and develop the probabilistic water body mapping algorithm based on the priori probability estimation. Firstly, we make the statistical model assumption about backscatter values based on Bayesian theory. Then, we classify the images based on cluster algorithm, calculate the prior probability of the water body mapping and estimate the parameters of the statistical model of water distribution.Thewater body probabilistic maps based on GF-3 images in Luquan and Xianning are calculated and then validated with GF-1 images. The algorithm is effective on high-precision probabilistic water body mapping of SAR images.

Building extraction via convolutional neural networks from an open remote sensing building dataset

JI Shunping, WEI Shiqing

2019, 48(4): 448-459. doi:10.11947/j.AGCS.2019.20180206

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Automatic extraction of buildings from remote sensing images is significant to city planning, popular estimation, map making and updating.We report several important developments in building extraction. Automatic building recognition from remote sensing data has been a scientific challenge of more than 30 years. Traditional methods based on empirical feature design can hardly realize automation. Advanced deep learning based methods show prospects but have two limitations now. Firstly, large and accurate building datasets are lacking while such dataset is the necessary fuel for deep learning. Secondly, the current researches only concern building's pixel wise semantic segmentation and the further extractions on instance-level and vector-level are urgently required. This paper proposes several solutions. First, we create a large, high-resolution, accurate and open-source building dataset, which consists of aerial and satellite images with both raster and vector labels. Second,we propose a novel structure based on fully neural network which achieved the best accuracy of semantic segmentation compared to most recent studies. Third, we propose a building instance segmentation method which expands the current studies of pixel-level segmentation to building-level segmentation. Experiments proved our dataset's superiority in accuracy and multi-usage and our methods' advancement. It is expected that our researches might push forward the challenging building extraction study.

A stereo visual odometry pose optimization method via flow-decoupled motion field model

WU Meng, HAO Jinming, FU Hao, GAO Yang, ZHANG Hui

2019, 48(4): 460-472. doi:10.11947/j.AGCS.2019.20180429

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For solving the optimization problem in vehicle ego-motion estimation in mobile mapping system (MMS) or autonomous vehicle(AV), the relationship between vehicle pose and optical flow is proposed to be utilized and all optical flow vectors are decoupled into 3 translational components, 3 rotational components and 1 depth component. The error influences on single component and combined components to vehicle pose estimation are derived. The validity of error separation models with single or combined components is verified through simulation and real-scene data experiments. The combined components error separation model is employed in the proposed flow-decoupled motion field based pose optimization algorithm for stereo visual odometry. Experiment results illustrate that, in conditions of almost the same calculation efficiency as the initial estimation process, this algorithm can reduce the average lateral direction error from 4.75% to 2.2%, which means the lateral direction error is reduced by 53.6%; and it can reduce the average forward direction error from 2.2% to 1.9%, which means the forward direction error is reduced by 15.4%.The results demonstrate that the lower cumulative error ratio can satisfy the requirement of real-time vehicle ego-motion estimation in low power dissipation and high efficiency situations in integrated navigation.

Measuring regional progress towards SDGs by combining geospatial and statistical information

CHEN Jun, PENG Shu, ZHAO Xuesheng, GE Yuejing, LI Zhilin

2019, 48(4): 473-479. doi:10.11947/j.AGCS.2019.20180563

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The 17 Sustainable Development Goals (SDGs) defined by the Transform our World:2030 Agenda for Sustainable Develepment represents a new coherent way of embracing economic prosperity, social inclusion, and environmental protection as an "indivisible whole". In order to ensure the implementation of this global agenda, the United Nations had proposed a systematic follow-up and review through indicators-based tracking and reporting of the progress with statistical and geospatial information towards SDGs at national, regional and global levels. This has posed many technical and coordination challenges, such as selection of appropriate indicators for a given nation or sub-nation regions, availability and acquisition of reliable data sets, spatio-temporal analysis with a geographical perspective, interaction between SDGs and cross-sector coordination. Although the international society has devoted great attention to this hot topic, most of them remain on the conceptual design and preliminary testing. There are very few good practices for a comprehensive measurement and assessment of progress towards SDGs with integration of statistical and geospatial information at nation or sub-national level. This paper presents the methodology and results of a pioneer project which measured the progress towards SDGs at a county level in China by combining integration of statistical and geospatial information. The major conclusions are ① the comprehensive progress towards SDGs in an entire administrative region can best be measured and assessed by integrating geospatial and statistical information; ② the Deqing county has made significant economic and social advances while maintaining a good ecological environment over the past few years. The results were released at the first United Nations World Geospatial Information Congress as a good practice and a live example to stimulate discussions and further actions on better supporting SDGs with geospatial information.

An incremental construction method of road network considering road complexity

LIU Jiping, ZHANG Yongchuan, XU Shenghua, QIAN Xinlin, QIU Agen, ZHANG Fuhao

2019, 48(4): 480-488. doi:10.11947/j.AGCS.2019.20180419

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Aiming at the problem of needing expensive field survey and a large number of subsequent indoor processing for traditional road network acquisition and update, a method for automatically generating road network from large-scale raw trajectory data is proposed. The road network is constructed in two steps:trajectory selection and road network incremental construction. The trajectory selection process divides the raw trajectory records and filters them by constructing a spatial, temporal and rule constraint model to eliminate noise and redundancy in the data, and forms a set of canonical trajectories; the road network incrementally construction process calculates the road complexity around the processing point based on the information entropy to automatically adjust the road segmentation parameters, and continuously adds the newly generated road segments to the road network, and simultaneously calculates road traffic information such as average traffic volume and speed, and traverses the points of each trajectory, repeats the above process, and finally gets the complete road network. The road network construction experiment was carried out through about 68.51 million trajectory data collected by 200 taxis in Kunming. The results were compared with the OpenStreetMap data, which proved the effectiveness of the proposed method. When compared with the existing methods, our method can extract higher quality road network with fewer nodes.

Polygon contour similarity and complexity measurement and application in simplification

CHENG Mianmian, SUN Qun, XU Li, CHEN Huanxin

2019, 48(4): 489-501. doi:10.11947/j.AGCS.2019.20180124

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On a comprehensive study concerning polygon contour similarity and complexity, in which the inner chord length, outer chord length, and average arc-to-chord length corresponding to multi-scale entities are extracted to construct chord-feature matrices. A multi-scale polygon contour similarity measurement model is developed. According to the frequency and amplitude of the edges, a complexity measurement model is constructed considering the ratio of the notch, relative increment of the perimeter of the convex shell, and relative increment of the area of the minimum envelope. After verifying the validity and effectiveness of the two models, the similarity variation rules for entities of different complexity at different scales are analyzed, and a general automation simplification flow based on similarity constraints is obtained. Results of the experiments show that the proposed method can set reasonable threshold parameters for the simplification algorithm, and improve the level of automation.

GPS trajectory agglomeration and refined road network extraction

WU Qunyong, WU Zufei, ZHANG Liangpan

2019, 48(4): 502-511. doi:10.11947/j.AGCS.2019.20180256

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Aiming at the shortcomings of low-accuracy in the use of GPS data to extract bidirection a roads and intersections, this paper proposes a trajectory agglomeration and refined roads extraction method that takes into account the position and travel direction to extracts refined road network. First,we remove the discrete and abnormal trajectory points from the original trajectory and insert the trajectory points into the trajectory segments by a certain step size, in order to improve the extraction accuracy of the intersection network.Second,we introduce the driving direction angle to express the driving direction of the vehicle at the track point, obtain its similar trajectory points set by considering the position and direction of the track point, calculate the offset distance of each track point in turn, and complete the track aggregation by iteratively offsetting the track points.Finally, we eliminate the track points that have not been successfully gathered, and use the Grid digitization method to extract the road network that can reflect the fine steering relationship of the roads from the trajectory data after gather. The trajectory agglomeration and road network extraction experiments were carried out with GPS data of Fuzhou taxis. The experimental results show that this method can effectively gather the GPS trajectories according to the direction of vehicle travel and the extracted road network is bidirectional roads, and can finely reflect the steering relationship of the roads at the intersections.

Overall calibration method of multibeam echo sounder installation biases based on terrain feature matching

LI Tie, ZHOU Fengnian, ZHAO Jianhu

2019, 48(4): 512-519. doi:10.11947/j.AGCS.2019.20180095

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The patch test method based on decoupling principle to determine MBES (multibeam echo sounders)installation biases often results in complex operation and low accuracy due to theoretical imperfections. Therefore, the overall calibration of the biases is proposed. Firstly, MBES sounding terrain is converted into grayscale image. Then, SIFT(scale-invariant feature transform) is used for matching related terrain images and founding matching point pairs. Finally, the inequality-constrained least square adjustment is used for obtaining the MBES installation biases by the matching point pairs coordinates. The experiment verifies the validation of this method in simplifying the implementation and improving the accuracy of determining these biases.

A collaborative simplification method for multiple coastlines based on the hierarchical triangulation network partition

ZHANG Lihua, TANG Lulu, JIA Shuaidong, DAI Zeyuan

2019, 48(4): 520-531. doi:10.11947/j.AGCS.2019.20180382

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The current automatic coastline generalization method only consideres one-line element, yet the relationship between the nearby elements is not effectively considered. Aiming at this, a synergistic simplification method for multiple coastlines based on the hierarchical triangulation network partition is proposed in this paper. Firstly, the constrained Delaunay triangulation is constructed to partition the regions that can be simplified. Then, a hierarchical binary tree model to structure the morphological characteristics of the above several coastlines and the spatial proximity between different coastlines is constructed. Finally, the small curved and curved invisible parts of the coastline are deleted according to the visual constraints, and the narrow part between the coastline itself or the different coastlines is exaggerated appropriately, and the automatic simplification of the coastline is realized. The experimental results show that relationships between the different coastline are considered, and the shortcomings of considering the coastline separately are overcome. Furthermore, under the condition of the multiple coastline in complex sea areas, the problem of collaborative simplification is solved, and the quality of the coastlines is improved obviously. The proposed method can be applied into more types of coastlines.

Research on the safety evaluation and key technologies for the expressway construction on old goaf of coal mine

GUO Qingbiao

2019, 48(4): 532-532. doi:10.11947/j.AGCS.2019.20180225

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Research on the complex system of geographical national conditions and its regionalization

XIE Mingxia

2019, 48(4): 533-533. doi:10.11947/j.AGCS.2019.20180234

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Algorithm study with GPS/BDS and PL high precise RTK positioning

LI Xin

2019, 48(4): 534-534. doi:10.11947/j.AGCS.2019.20180258

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Noise characteristics and seasonal variations of IGS site coordinate time series

XU Chang

2019, 48(4): 535-535. doi:10.11947/j.AGCS.2019.20180275

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Research on change detection method in multi-temporal polarimetric SAR imagery

ZHAO Jinqi

2019, 48(4): 536-536. doi:10.11947/j.AGCS.2019.20180281

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