Table of Content

20 October 2018, Volume 47 Issue 10

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Determination of the Vertical Deviation for China Height Datum with Coordinates of Dagang Tidal Gauge

WU Fumei, WEI Ziqing, LIU Guangming

2018, 47(10):  1295-1300.  doi:10.11947/j.AGCS.2018.20170051

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Determining the vertical deviation for a local height datum relative to the geoid is an important approach to the unification of the Global Vertical Datum. In this paper, we aim at direct determination of the vertical deviation for China Height Datum with the coordinates of Dagang Tidal Gauge. First, the principles for determination of the vertical deviation with the coordinates of Dagang Tidal Gauge are introduced. Then the methods and the processes for measuring and calculating the coordinates of Dagang Tidal Gauge are elaborated. Next EGM2008 and EIGEN-6C4 models are used to calculate the gravity potential with the coordinates of Dagang Tidal Gauge, and the results are compared with those obtained with GPS/Leveling data. It is found that the gravity potential obtained from EGM2008 model is more reliable than that from EIGEN-6C4 model, and the vertical deviation for China Height Datum with the coordinates of Dagang Tidal Gauge is 0.344 m, which is 0.006 m smaller than that with GPS/leveling data.

On an Improved Iterative Reweighted Least Squares Algorithm in Robust Estimation

FANG Xing, HUANG Lixiong, ZENG Wenxian, WU Yun

2018, 47(10):  1301-1306.  doi:10.11947/j.AGCS.2018.20170576

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In geodesy,classical least squares (LS) estimation methods rely heavily on assumptions which are often not met in practice.In particular,it is often assumed that the data errors are zero mean distributed,at least appproximately.Unfortunately,when there are outliers in the data,the classical LS estimators frequently have meaningless performance.In this case,robust estimation such as M-type estimation is usually applied,which is numerically implemented by a so called iterative reweighted least squares algorithm.In the current reweighting process,however,the equivalent normal matrix is required to be inverted in every iteration,which needs an expensive computation demand,especially when the number of the unknown parameters is large.Therefore,in this contribution,the numerical process of the iterative reweighted least squares algorithm is essentially improved,which is mainly represented by avoiding the inversion of the equivalent normal matrix.The numerical example shows that the improved version is performed much superior to the previous one.

Recovery of Bathymetry over Philippine Sea by Combination of Multi-source Gravity Data

FAN Diao, LI Shanshan, MENG Shuyu, XING Zhibin, FENG Jinkai, ZHANG Chi

2018, 47(10):  1307-1315.  doi:10.11947/j.AGCS.2018.20170423

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According to the "theoretical admittance" and the "observation admittance" of the actual data,the theoretical value of effective elastic thickness in the study area was 10 km. Combining the gravity anomaliesand vertical gravity gradient anomalies,the admittance function is used to construct the 1'×1' bathymetry model over the Philippine Sea by using the adaptive weighting technique.It is found that the accuracy of the bathymetry model constructed is the highest when the ratio of inversion result of vertical gravity gradient anomalies and inversion result of gravity anomalies is 2:3.At the same time,using multi-source gravity data to predict bathymetry could synthesize the superiority of gravity anomalies and vertical gravity gradient anomalies on the different seafloor topography,and the accuracy is better than bathymetry model that only used gravity anomalies or vertical gravity gradient anomalies.Taking the ship test data as the checking condition,the accuracy of predicting model is slightly lower than that of V18.1 model and improved by 27.17% and 39.02% respectively, compared with the ETOPO1 model and the DTU10 model.Checkpoints which the absolute value of the relative error of the predicting model are in the range of 5% accounted for 94.25% of the total.

The Accuracy Analysis of GPT2w at the Antarctic Area

KONG Jian, YAO Yibin, SHAN Lulu, WANG Zemin

2018, 47(10):  1316-1325.  doi:10.11947/j.AGCS.2018.20170487

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GPT2w (global pressure and temperature 2 wet) is one of the widely used empirical troposphere models, which is usually used to compute the tropospheric parameters, such as pressure, temperature, water vapor pressure etc. In order to analyze the model accuracy around the Antarctic Pole area, the actual data from the radiosonde stations and the measured data during the Chinese 33th Antarctica Expedition are used to test the model parameter's accuracy on different height level. Based on the comparison with the data from the radiosonde stations and GPT2w, it is found that on ground level, the model accuracy at Antarctic Pole area is high, which is consistent with the accuracy at other areas; then by comparing the statistics in January and July, it is found that Bias and RMS showed seasonal characteristics; at the same time, it is found that there is a large error in the vertical direction of the model, which shows that as the height increases, the accuracy decreases and gradually stabilizes.Before the comparison with the measured data and GPT2w, the ECMWF(European Centre for Medium-range Weather Forecasts)data are used to confirm the reliability of the measured data, while the results showed that the two dataset consistent with each other. Meanwhile, by comparison, it is found that the GPT2w accuracy among a day is equal to monthly average accuracy on ground level, but the vertical accuracy decreases with the increase of height compared with the accuracy of the warm season, which shows that there is a certain impact on the accuracy of the model without considering the variation of the daily period. zenith tropospheric delay (ZTD) calculated by sounding data is used to analyze the accuracy of GPT2w. The result shows that the accuracy of GPT2w ZTD in the Antarctic is centimeter accuracy, which is equivalent to the accuracy of other areas in the world.

Estimation and Application of Single Difference FCB for Full Constellation Using One Reference Satellite

JIAO Bo, HAO Jinming, LIU Weiping, ZHANG Hui, WEN Xufeng, SHI Yishuai

2018, 47(10):  1326-1336.  doi:10.11947/j.AGCS.2018.20170519

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The single-difference FCB is applied to the ambiguity resolution of precise point position,which can improve the positioning accuracy and speed up the convergence.However,due to the earth block,one satellite cannot form common views with other satellites,which means one reference satellite cannot get all the single-difference FCB.If single-difference FCB of multiple reference satellites is broadcast as a supplement,the burden of data transmission will be increased.Considering the availability and data volume,this paper proposes an improved FCB generation method.Based on the principle of differential transfer,it converts the single-difference FCB's of different reference satellites into a common one.Then it uses the robust estimation based on the GPHASE initial value to merge the converted FCB.In this paper,15 days data from IGS monitoring network are selected to generate the improved FCB and the fixed solution PPP is implemented.The experimental results show that the improved single-difference FCB of one reference satellite can meet the application requirements.Stability and availability of the improved FCB is better than that of traditional single-difference FCB,and the difference compared with existing FCB product is less than 0.04 cycle.Using the improved FCB,users can achieve a fixed solution PPP with a horizontal accuracy better than 1 cm and a vertical accuracy better than 2 cm in static mode.The kinematic PPP can achieve the 3D positioning accuracy within 5 cm in about 15 minutes.

Establishment of Statistical Correction Model for Vertical Annual Variations of Global GPS Stations

FU Yanbo, SUN Fuping, ZHU Xinhui, LIU Jing

2018, 47(10):  1337-1345.  doi:10.11947/j.AGCS.2018.20170616

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The research and modeling of nonlinear variations of GPS stations coordinates are effective ways to weaken nonlinear motion of the stations. However,due to the diversity and complexity of nonlinear variations of stations' coordinates,the theoretical correction model contained multiple mechanisms has not been established to weaken the nonlinear motion of GPS stations.In this paper,global distribution regularity of annual terms of vertical coordinates of stations was discovered based on the measured vertical coordinates residuals of nearly 500 GPS stations,two statistical correction models of annual variations based on measured data were respectively constructed for the northern and southern hemispheres.The experiments show that the statistical correction model proposed in this paper can weaken 30%~50% vertical coordinate residuals of most GPS stations in the world.

Jitter Detection for High Resolution Satellites Based on Phase Correlation with Local Frequency Analysis

TONG Xiaohua, YE Zhen, LIU Shijie, XIE Huan, JIN Yanmin, CHEN Peng

2018, 47(10):  1346-1352.  doi:10.11947/j.AGCS.2018.20180249

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Jitter is a crucial error source that undermines the geometric and radiometric performance of satellite imagery.In order to enhance the feasibility and trust of retrieving jitter from imagery,this paper proposes an intelligent jitter detection method using parallax observation based on phase correlation with local frequency analysis.Through connecting structural image representation with phase correlation,the local and global phase information is fully utilized to reduce the influence of radiometric variation,noise and other interferences on subpixel translation estimation.The subpixel phase correlation is integrated into the framework of jitter detection using parallax observation,which ensures the accurate and robust dense matching and achieves effective jitter detection.The effectiveness of the proposed method is demonstrated by method comparison using images with realistic radiometric difference as well as jitter detection test using ZY-3 images.The promising results indicate that,the subpixel phase correlation method with local frequency analysis outperforms other state-of-the-art methods in the presence of radiometric difference and noise,achieving a matching accuracy of 0.05 pixels,and the proposed jitter detection method effectively estimates the jitter information of ZY-3 satellite.

Forest Above-ground Biomass Estimation for Rugged Terrain by Using ESAR Polarization Data

ZHANG Haibo, WANG Changcheng, ZHU Jianjun, FU Haiqiang

2018, 47(10):  1353-1362.  doi:10.11947/j.AGCS.2018.20170120

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The influence of the ground slope on radar backscatter has been proven to be greater for lower radar frequencies due to deeper canopy penetration. In order to solve this problem and obtain accurate estimation of forest above-ground biomass (AGB) in the region of rugged terrain, the analytic model integrating the topographic factors was presented based on the modified water-cloud model (WCM) and the relationship between different backscattering coefficients and the forest AGB using the airborne P-band full polarimetric SAR (PolSAR) data acquired by E-SAR. In this study, genetic algorithm (GA) was used to determine the optimal parameter values for the model, the terrain slope was divided into three grades (0~5°、5°~10°、≥ 10°). Then we analyzed the reliability and stability of the model under the condition of different slope. Meanwhile, in order to determine advantage of the water-cloud analysis model in evaluating AGB, we used common models include linear model、logarithm model、exponential model、quadratic model to comparison and analysis. Through the comparative analysis, we found that when the forest AGB at lower level, the variational trend of backscatter coefficients (HH、HV、VV) kept the same with the vatiational trend of AGB. With the increase of AGB values, this consistency in HV backscatter coefficient values to keep alone, therefore, HV polarization was the best to estimate biomass in the complex terrain region. The terrain has a great impact on estimating forest AGB, a phenomenon was that the correlation of backscatter coefficients and forest AGB decreased with the increase of ground slope. The capabilities of estimate biomass in the five models were different, from strong to weak was that water-cloud analysis model > quadratic model > logarithm model > exponential model > linear model. Meanwhile, through comparing the change of the determination coefficients (R²), these models were found that have different stabilities to estimate forest AGB in different slope levels. When the slope changed from 0~5° to 5°~10°, the stability from strong to weak was water-cloud analysis model > quadratic model > logarithm model > exponential model > linear model. With the slope from 5°~10° to ≥ 10°, this sequence became that water-cloud analysis model > exponential model > linear model > quadratic model > logarithm model. In addition, between 0~5° to ≥ 10°, this sequence was water-cloud analysis model > quadratic model > linear model > exponential model > logarithm model respectively. Although, there was different sequence in five models, the stability of the water-cloud analysis model was higher than other models. So, we tried to use water-cloud analysis model to estimate forest AGB for the study area. The result showed that the R² between the field AGB and estimated AGB was 0.597, the root mean squared error (RMSE) was 30.876 t/hm², the overall accuracy was 77.40%.

Line Matching Based on Discrete Description and Conjugate Point Constraint

OUYANG Huan, FAN Dazhao, JI Song, LEI Rong

2018, 47(10):  1363-1371.  doi:10.11947/j.AGCS.2018.20170231

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Many unfavorable factors may hinder the line matching, such as fracture, deformation or occlusion occurred in line extraction. In order to overcome these problems, a novel method for line matching based on discrete description and conjugate point constraint is proposed. Firstly, the method employs the homography constraint together with epipolar constraint to determine candidate lines. Then, the initial line matching results are obtained by the distribution statistics of the conjugate points on the line. Finally, the mismatching in matched line pairs is eliminated by the similarity verification of line-point affine invariant. Extensive experiments on AMC580 aerial image set demonstrate the better performance of the proposed method as well as its superiority in curve matching and many-to-many matching. Compared with existing line matching methods, the proposed method can obtain more accurate line matching results under changes of image scale, brightness, occlusion, rotation, and achieves a performance of 90% higher matching correctness.

Digital Surface Model Generation for High Resolution Satellite Stereo Image Based on Modified Semi-global Matching

YANG Xingbin, LÜ Jingguo, JIANG Shan, ZHANG Danlu

2018, 47(10):  1372-1384.  doi:10.11947/j.AGCS.2018.20180091

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A method is proposed for generating digital surface model (DSM) of high resolution satellite imagery (HRSI) based on modified semi-global matching (SGM) algorithm.Firstly,the system error of the rational function model is compensated by using the geometric constraint relation between the image connection points.Based on the compensation model,the image is divided into blocks.The projection trajectory method is used to obtain the image pairs of the images.In the dense matching stage,the disparity map is computed using semi-global matching by layer after building the pyramids images,and an expansion corrosion algorithm for disparity graphs,which takes into account the image texture information,is introduced to constrain the range of parallax search,increase the number of effective pixels at the edge of the parallax map and reduce the memory overhead and computation time required for the algorithm.In the post processing stage of disparity image,the edge information of disparity image is protected by weighted median filtering algorithm.Finally,the DSM is acquired based on the forward intersection.The stereo images of World View 3 and ZY-3 to experiment are selected.The experimental results show that the DSM accuracy obtained by this method is nearly 1.5 times higher than that of GSD in elevation direction,and the edge characteristics of the object are maintained well.The algorithm is computationally efficient and has relatively low memory overhead.

Object-oriented Battlefield Environment Simulation Process Object Model Based on Task-driven

ZHU Jie, YOU Xiong, XIA Qing

2018, 47(10):  1385-1395.  doi:10.11947/j.AGCS.2018.20170587

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Battlefield environment simulation process is an important part of battlefield environment information support,which needs to be built around the task process.At present,the interoperability between battlefield environment simulation system and command and control system is still imperfect,and the traditional simulation data model cannot meet war fighters' high-efficient and accurate understanding and analysis on battlefield environment's information.Therefore,a kind of task-orientated battlefield environment simulation process model needs to be construed to effectively analyze the key information demands of the command and control system.The structured characteristics of tasks and simulation process are analyzed,and the simulation process concept model is constructed with the method of object-orientated.The data model and formal syntax of GeoBML are analyzed,and the logical model of simulation process is constructed with formal language.The object data structure of simulation process is defined and the object model of simulation process which maps tasks is constructed.In the end,the battlefield environment simulation platform modules are designed and applied based on this model,verifying that the model can effectively express the real-time dynamic correlation between battlefield environment simulation data and operational tasks.

The Evaluation Method for Ecosystem Service Value Based on National Census Geography Results

XU Zimeng, LI Guangyong, ZHOU Xu, CHENG Tao, JIANG Guanghui, BAI Ju

2018, 47(10):  1396-1405.  doi:10.11947/j.AGCS.2018.20180212

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Ecosystem services are directly related to the well-being of human beings, and it is one of the important components of the construction of ecological civilization in China. There is still a lack of regular ecological service value accounting at the national scale because of the limitations of precision and time series data. In this study, we rebuilt the representation relationship between land cover data of geographical conditions and ecosystem classification based on the internal structure and function of ecosystem type, and the semantic concept of content index. The vector data of China's terrestrial ecosystem are produced. Then, we used equivalent factor model through the optimization of the vegetation feature index that reflect the vegetation physiological characteristic (EVI, NPP and growing-season length), and introduced geo grid spatial expression technology suitable for multi granularity transformation under different scales is applied, carrying out the production design of ecosystem service value data set based on vectorization data of national census geography. Production design realizes the precision and normalization of ecosystem service value accounting, meets the needs of dynamic monitoring of ecosystem service value under different scales, and completes the production of ecosystem service value data set under the national scale. According to the above ecosystem service value accounting method, the total ecosystem service value and the supply, regulation, support and cultural service sub function service value 1 km×1 km grid data are produced. The total terrestrial ecosystem service value of China in 2015 is 40.25×10¹² CNY. The result is reliable and can meet the requirements of different scales for granularity transformation compared with earlier results. It will provide data support for the current national scale of horizontal ecological compensation policy.

A Line-surface Integrated Algorithm for Underwater Terrain Matching

ZHANG Lihua, LIU Xianpeng, JIA Shuaidong, SHI Yan

2018, 47(10):  1406-1414.  doi:10.11947/j.AGCS.2018.20170673

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The current underwater terrain surface matching algorithm,which uses Hu moment as similarity index, cannot gain fairly precious location due to its disadvantage in detecting slight difference.To solve this problem,a line-surface integrated terrain matching algorithm is presented.Firstly,the similarity evaluation method of traditional terrain contour matching (TERCOM) algorithm is improved,and strategy used to select the matching regions is developed.Then,a surface matching algorithm based on geometric similarity is established to find the optimum matching of real terrain.Finally,an integration means of the "line matching algorithm" and "surface matching algorithm" based on fixed threshold is proposed.Experimental results show that the proposed algorithm can obtain much higher location precision and better robustness than the surface underwater matching algorithm based on Hu moment.

An Adaptive Simplification Method of SVP Based on Area Difference

ZHENG Gen, ZHANG Hongmei, FENG Lei, ZHAO Jianhu

2018, 47(10):  1415-1423.  doi:10.11947/j.AGCS.2018.20170232

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An adaptive method based on area difference is proposed. Firstly, the relationship between area difference and sound ray tracking bias is studied and the model is built. Then the simplification method and procedure of SVP are provided, which are based on the constraint of sound ray tracking accuracy. Finally, a deep water experiment is conducted to verify the proposed method and the simplification process is easily achieved without manual intervention. It improves the efficiency of bathymetric data processing remarkably to carry out ray-tracing with simplified sound velocity profile.

A Robust Weighted Total Least Squares Method

GONG Xunqiang

2018, 47(10):  1424-1424.  doi:10.11947/j.AGCS.2018.20180105

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SAR Deformation Measurement, Interpretation and Data Assimilation in Geological Disaster Monitoring

JIANG Yanan

2018, 47(10):  1425-1425.  doi:10.11947/j.AGCS.2018.20170565

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Co-location Researches on Urban Public-service Facilities

YAO Xiaojing

2018, 47(10):  1426-1426.  doi:10.11947/j.AGCS.2018.20170580

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Estimation of Exposed Carbonate Rock Fraction with Remote Sensing Imagery: A Case Study of Jianshui County

XIE Xiangjian

2018, 47(10):  1427-1427.  doi:10.11947/j.AGCS.2018.20170615

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Research on Information Extraction and Spatial Sampling Methods of Accuracy Assessment for Woodlands

DONG Shiwei

2018, 47(10):  1428-1428.  doi:10.11947/j.AGCS.2018.20180320

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