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Acta Geodaetica et Cartographica Sinica 2020 Vol.49 Please wait a minute... For Selected: Download Citations EndNote Ris BibTeX Toggle Thumbnails Select Three multi-frequency and multi-system GNSS high-precision point positioning methods and their performance in complex urban environment GENG Jianghui, CHANG Hua, GUO Jiang, LI Guangcai, WEI Na Acta Geodaetica et Cartographica Sinica    2020, 49 (1): 1-13.   DOI: 10.11947/j.AGCS.2020.20190106 Abstract （2062）   HTML （119）    PDF（pc） （25129KB）（922）       Knowledge map    Save High-precision applications, such as intelligent transportation and automated driving in urban environment, require a dynamic positioning accuracy at decimeter to centimeter level. However, GNSS performance (such as availability and positioning accuracy) in urban environments is strongly degraded by man-made and natural objects that obstruct satellite signals. Taking advantage of the available multi-frequency and multi-system GNSS (GPS/BDS/Galileo/QZSS) data, we adopt the new single-epoch PPP wide-lane ambiguity fixing method (PPP-WAR) for vehicle dynamic positioning. It is compared with the traditional PPP method and wide-area pseudorange enhanced precision positioning method in three typical urban environments with different complexity, including a road in metropolitan area, a narrow road in small town and an open road in industrial area. The integrity of triple-frequency GNSS data is currently up to 94% in urban area, which assures that single-epoch PPP-WAR method is applicable in complex urban area. It's shown that a positioning accuracy of 0.41 m in the horizontal direction is achieved using the single-epoch PPP-WAR method in the narrow road in town with the threshold of 3.0 m, which satisfies the accuracy requirement at decimeter level. The accuracy is largely improved by 53.9% and 21.2% compared with those of wide-area pseudorange enhanced precision positioning solutions and traditional PPP solutions, respectively. The availability of three methods in metropolitan area is higher than 70%, as well as more than 90% in small town and industrial area. The availability of PPP-WAR and traditional PPP can still reach ~70% with a strict threshold of 0.5 m. Four typical features (i.e. tunnels, crossovers, street trees and skyscrapers) in urban environment have the least impact on the performance of single-epoch PPP-WAR among the three methods. In sum, single-epoch PPP-WAR method has the best performance in complex urban environment with more obstructions, while traditional PPP method is the best in open urban environment with less obstructions. Reference | Related Articles | Metrics Select Optimized estimation of foF2 using GNSS data ingestion to NeQuick model during magnetic storm HAN Ling, WANG Jiexian, CHEN Yanling, LIU Jingbin, LI Haojun Acta Geodaetica et Cartographica Sinica    2020, 49 (1): 14-23.   DOI: 10.11947/j.AGCS.2020.20180260 Abstract （1083）   HTML （22）    PDF（pc） （9994KB）（297）       Knowledge map    Save The critical frequency of F2 is an important parameter for high frequency communications. Ionosonde measured foF2 is an effective way but it would be affected by geomagnetic storm which will even lead to the data missing. NeQuick model could estimate the TEC and foF2.But the accuracy would be degraded during geomagnetic storm. Using the dual frequency GNSS data from the CMONOC(Crustal Movement Observation Network of China)and applying the regional polynomial model, the accurate TEC could be retrieved. Based on the condition that the sum of the squared errors is the minimum, the effective ionized parameter Az could be estimated using the calculated TEC. Using the NeQuick model input by ionized parameter Az, the TEC and foF2 could be retrieved. Using the observations of five ionosonde stations located in different latitudes is in China, the result indicated that the TEC RMS improved 20%~40%, and the foF2 RMS improved 10%~25%. This method could improve the TEC and foF2 accuracy. It showed the benefit of low cost. So it could be considered as the alternative way to the ionosonde observations especially for the foF2 data missing period. Reference | Related Articles | Metrics Select Post-maneuver orbit determination based on the predicted clocks CHEN Qian, CHEN Junping, WU Shan, ZHANG Yize, YU Chao Acta Geodaetica et Cartographica Sinica    2020, 49 (1): 24-33.   DOI: 10.11947/j.AGCS.2020.20190078 Abstract （1199）   HTML （17）    PDF（pc） （9529KB）（224）       Knowledge map    Save The BDS system is designed as a GEO/IGSO/MEO mixed constellation. Satellite maintaining operation is performed every 7 to 10 days for GEO/IGSO satellites. With the maneuver satellite's status being unhealthy in the post-maneuver period, which lasts 5~6 hours, the BDS system usability is affected. In the long unhealthy periods, observation data together with satellite/station clocks are accumulated until the processed orbits meet precision requirement. To shorten the satellite's unhealthy time during post-maneuver, we propose an orbit determination method making use of the predicted satellite/station clocks. With the clocks being modeled with high precision, data of longer observation arc could be used, thus improve the orbit accuracy. In the modeling of satellite and station clocks, the reference inconsistency between the two-way satellite time frequency transfer(TWSTFT) and dynamic precise orbit determination(POD) techniques are considered. Three satellite maneuver events in November 2018 are analyzed. Results show that the satellite unavailability time could be shortened by at least 1 hour. And it improves the accuracy of orbit prediction with maximum of 84.82% for the first group of orbits in post-maneuver. For the POD from 3h to 8h after maneuver, the mean improvement of orbit prediction accuracy is of 26.06%(C01),31.58%(C04) and 9.95%(C03) by using the proposed method. Reference | Related Articles | Metrics Select A method for determining the weight in weighted mixed estimation SONG Yingchun, SONG Caiwei, ZUO Tingying Acta Geodaetica et Cartographica Sinica    2020, 49 (1): 34-41.   DOI: 10.11947/j.AGCS.2020.20180359 Abstract （1267）   HTML （19）    PDF（pc） （926KB）（389）       Knowledge map    Save In this paper, multi-source observation models with various heteroscedastic and combined adjustment methods in geodesy are summarized. It shows that the mixed estimation method can be used for measurement data fusion, and can balance the influence of additional information and sample information on parameter estimation. By calculating the weights to minimize the trace of the covariance matrix of parameter estimation, an optimal selection method of weights is given. This paper extends the existing weighted mixing method so that the given method are not limited by the prior unit weight variance, and can be effectively applied to large measurement data processing. Reference | Related Articles | Metrics Select Accuracy analysis of IRI2016 international reference ionosphere at altitude of 60~100 km CHENG Huhua, ZHAN Caiju, ZHAO Liang, WANG Yibai, XIU Xingtao Acta Geodaetica et Cartographica Sinica    2020, 49 (1): 42-54.   DOI: 10.11947/j.AGCS.2020.20180508 Abstract （1419）   HTML （23）    PDF（pc） （4363KB）（473）       Knowledge map    Save The low-altitude ionosphere (60~100 km) has great influence on radio propagation and measurement. IRI2016 is a widely used international reference ionospheric model. Therefore, it is of great practical significance to analyze the reliability of its electron density at an altitude of 60~100 km. Based on electron density data (2014-2016) provided by medium-frequency (MF) radar in Langfang, the reliability of electron density of IRI2016 model at an altitude of 60~100 km in the mid-latitude was quantitatively analyzed in this study using deviation, absolute difference, correlation coefficient, relative deviation and Lomb-Scargle periodogram. At the altitude of 60~100 km in the mid-latitude, the results showed as follows:① The deviation, absolute difference and relative deviation of electron density was closely related to season. At the altitude of 86~100 km, they increased rapidly with the increase of altitude. In addition, correlation coefficient was also closely related to season, but presented an alternation of increasing and decreasing with the increase of altitude. ② The electron density accuracy of the IRI2016 model was related to solar activity and geomagnetic conditions, and had the highest accuracy under low solar activity and magnetic tranquility. ③ The electron density of MF radar and IRI2016 model at the altitude of 82~84 km both showed significant (verified by 90% significance test) quasi-diurnal tidal wave and quasi-8-hour gravity wave. Meanwhile, IRI2016 model presented significant quasi-semidiurnal tidal wave, which was not found in MF radar. At the altitude of 86~92 km, the electron density of both MF radar and IRI2016 model had significant quasi-diurnal tidal wave and quasi-semidiurnal tidal wave, but no quasi-8-hour gravity wave. ④ The electron density of both MF radar and IRI2016 model showed differences in significant wave period and power spectrum at the same altitude, and the significant wave period and power spectrum had differences among different altitudes. ⑤ Quasi-diurnal tidal wave played a main role in the change of the electron density of both MF radar and IRI2016 model at the altitude of 82~92 km. Quasi-8-hour gravity wave played a secondary role at the altitude of 82 km, and quasi-semidiurnal tidal wave played a secondary role at the altitude of 86~92 km. Reference | Related Articles | Metrics Select Abnormal data detection and process by using BDS satellite offset semiparametric adjustment model LI Wentao, YAN Xiong, XIA Lei, REN Qingyang, CHEN Jie, PAN Xiong Acta Geodaetica et Cartographica Sinica    2020, 49 (1): 55-64.   DOI: 10.11947/j.AGCS.2020.20180384 Abstract （1185）   HTML （17）    PDF（pc） （3614KB）（448）       Knowledge map    Save In view of the high frequency of abnormal data such as clock jump, gross error and so on in the BeiDou satellite clock offset data, this paper introduces the semiparametric adjustment model to the processing of the clock offset data of BDS. First of all, when considering the system error, we improved the common clock offset model. Secondly, when considering the abnormal data and the system error comprehensively, we use the compensation of principle of least squares and the extreme value solving method, the relation expression of estimated value of the parameters and non-parameters before and after the separation of the abnormal data and the corrected values of the corresponding observation values is derived in detail, and separation of the fixed value of the abnormal data, the parameter solution and the system error is realized. On this basis, the Cook distance is introduced, the Cook distance of parameter components and nonparametric components and the mixed Cook distance are presented to determine the location of the abnormal value. And the selection method of some parameters and the corresponding treatment measures are presented to achieve the location and fixed value of the anomaly data of the satellite clock offset and the separation of some system errors. Finally, the comparison is conducted by the method adopted in this paper and common method using the precision clock offset data of the BeiDou satellite, which has a sampling interval of 5 min from the GNSS center of Wuhan University. The experimental results show that the proposed method can effectively identify abnormal value in the satellite clock and deal with it, and effectively overcome the deficiency of the anomaly detection method based on the empirical threshold difference, and this method has a good detection effect for the abnormal clock offset data of smaller magnitude. To a certain extent, it has enriched the existing BDS clock offset data quality control method. Reference | Related Articles | Metrics Select Land cover classification of polarimetric SAR with fully convolution network and conditional random field ZHAO Quanhua, XIE Kailang, WANG Guanghui, LI Yu Acta Geodaetica et Cartographica Sinica    2020, 49 (1): 65-78.   DOI: 10.11947/j.AGCS.2020.20190038 Abstract （1300）   HTML （55）    PDF（pc） （5427KB）（444）       Knowledge map    Save Aiming at the problems of low classification accuracy and poor effect in the traditional fully convolution network (FCN), and insufficient consideration on the scattering characteristics of ground object features in the traditional polarimetric synthetic aperture radar (PolSAR) land cover classification methods. To overcome this limitation, this paper proposes a land cover classification algorithm of polarimetric SAR with improved FCN and conditional random field (CRF). First of all, the Freeman and Pauli decompositions are used to model the full-polarimetric SAR image to obtain the scattering features of scattering mechanisms, and Freeman decompositions are referenced to obtain the main scattering object corresponding to the main scattering component. Learning from the FCN-Vgg19-8s network with excellent performance in the field of image classification, and considering the large amount of high-level convolution parameters and the insufficient optimization of low-level convolution model parameters, Then an improved FCN, named FCN-MD-8s, is designed though constructing multi-scale convolution group and cost function in the upper and middle layers based on FCN-Vgg19-8s to guarante dimensionality reduction and optimization of overall model parameters. Additionally, FCN-MD-8s network is trained and tested for scattering mechanisms from Freeman decomposition by Cascade-migration-learning structure. Afterwards, according to the main scattering feature corresponding to the main scattering component, the main feature object is extracted from each component prediction image to obtain a component classification result. The result of each component classification is superimposed to gain a global rough classification. Finally, the fully-connected CRF with false color image, which is visualized by Pauli coherent decomposition, is used to transfer full image information over global rough classification for fine classification. The qualitative and quantitative analyses of classification results demonstrate that the proposed algorithm has effectiveness and feasibility. Reference | Related Articles | Metrics Select Using DEM as full controls in block adjustment of satellite imagery CAO Hui, TAO Pengjie, LI Haihong, ZHANG Zuxun Acta Geodaetica et Cartographica Sinica    2020, 49 (1): 79-91.   DOI: 10.11947/j.AGCS.2020.20190226 Abstract （1491）   HTML （67）    PDF（pc） （12349KB）（870）       Knowledge map    Save An algorithm is proposed in this study which directly uses digital elevation model (DEM) as full controls in block adjustment of satellite images, it is an application and extension of "cloud control" in photogrammetry. Different from the indirect geo-referencing method based on the registration of image-derived DSM or DEM with reference DEM, a DEM is considered as full geometric constraints and directly introduced into the block adjustment of satellite images based on the RFM model, by minimizing the squared sum of distances from tie points to the terrain surface described by DEM. By using DEM as exclusive control, the horizontal and vertical positioning accuracies of stereo satellite images can be upgraded without any ground control points (GCPs). A total of 330 stereo scenes of Chinese Mapping Satellite-1 images covering the whole area of Shandong Province are used for experimental tests, and three different open source DEM data of 1″ grid AW3D30, ASTER GDEM and 3″ grid SRTM GL3 are used as control data, respectively. The adjustment results are validated by using 100 well-distributed ground check points. Experiments show that the positioning accuracy is depended on the accuracy of DEM itself. While using AW3D30 as full controls, which is the most accurate one among the three global DEMs in experiments, the block adjustment accuracy of 4.9 m (about 1 pixel) in horizontal direction and 2.8 m in vertical direction can be achieved, respectively. Which is similar with the results of using 100 GCPs. It is proved that the effectiveness and feasibility of using DEM instead of ground control points as controls for block adjustment. Reference | Related Articles | Metrics Select Fast visibility detection without specifying the user-defined biases in multi-view texture mapping HUANG Xiangxiang, ZHU Quansheng, JIANG Wanshou Acta Geodaetica et Cartographica Sinica    2020, 49 (1): 92-107.   DOI: 10.11947/j.AGCS.2020.20180468 Abstract （1213）   HTML （21）    PDF（pc） （39338KB）（319）       Knowledge map    Save The Z-buffer and ray-tracing algorithms are the two popular approaches used in visibility handling for multi-view based texture mapping. However, the accuracies of the two algorithms are limited by the user-defined biases. We propose a solution in which no biases are specified. First, a shader-based rendering is designed according to the projection parameter of oblique photogrammetry to generate each view's initial visibility map (IVM). The fully occluded primitives will be excluded by the depth test of graphics pipeline.Second, projection coverage refinement (PCR) is given to the visible primitives in IVM based on vector rasterization criterion and pixel depth. Last, lazy projection (LP) and iterative vertex-edge sampling (IVES) are proposed to distinguish the partially visible and fully visible primitives. We use two datasets to prove our method's validity. The experimental results show that our method has a better performance than the mainstream algorithm. Reference | Related Articles | Metrics Select Oblique image matching algorithm based on adaptive initial object patch ZHANG Chunsen, ZHANG Qiyuan, GUO Bingxuan, XUE Wanchang Acta Geodaetica et Cartographica Sinica    2020, 49 (1): 108-116.   DOI: 10.11947/j.AGCS.2020.20190050 Abstract （1185）   HTML （25）    PDF（pc） （10904KB）（285）       Knowledge map    Save In order to solve the problem of low degree of image connection points and too few aero triangulation points with large depth discontinuity or difference when using the least square image matching method based on object patch to match oblique images, an algorithm of oblique image matching based on adaptive initial object patch is proposed. The algorithm uses the initial values of interior and exterior orientation elements of the oblique image and the object points generated in the matching process, and adaptively calculates the elevation of the object patch and the initial value of the normal vector direction angle by the method of multi-patch forward intersection and object variance partition. Then it solves the problem that the low accuracy initial value of the oblique image with the least squares image matching method of the object patch is not easily matched to corresponding points when matching the oblique image. Finally, two groups of oblique images are matched by the proposed method and the least square image matching method, in which the initial state of the object patch is horizontal object patch, respectively, to verify the effectiveness of the proposed method. Reference | Related Articles | Metrics Select Comparison of LM and EM parameter optimization methods for airborne laser bathymetric full-waveform decomposition GUO Kai, LIU Yanxiong, XU Wenxue, HE Xiufeng, ZHANG Ziyin, LIU Haitao Acta Geodaetica et Cartographica Sinica    2020, 49 (1): 117-131.   DOI: 10.11947/j.AGCS.2020.20180242 Abstract （1548）   HTML （8）    PDF（pc） （6962KB）（287）       Knowledge map    Save As operating environment and scanning conditions would affect the accuracy of the parameters of initial waveform decomposition, it is necessary to use some optimization method to adjust the initial parameters for making the results more precise. With the measured and simulated data, the strategies of Levenberg-Marquardt (LM) and expectation-maximization (EM) have been chosen typically in this paper. It is studied that the features of the waveform fitting precision, the scanning condition response and the depth of the deviation in the same initial parameters condition. The accuracy and stability of the data processing results has been discussed in detail, and the main technical features and the difference of the results of the two methods has been summarized in this paper. Reference | Related Articles | Metrics Select Study on the influence of cloud adjacency effects on the aerosol optical depth retrieval and its reducing method HE Junliang Acta Geodaetica et Cartographica Sinica    2020, 49 (1): 132-132.   DOI: 10.11947/j.AGCS.2020.20190060 Abstract （900）   HTML （31）    PDF（pc） （661KB）（395）       Knowledge map    Save Related Articles | Metrics Select Long-term evolution process and mechanisms of wetland ecosystem in the Yangtze River estuary using time-series multi-sensor remote sensing data AI Jinquan Acta Geodaetica et Cartographica Sinica    2020, 49 (1): 133-133.   DOI: 10.11947/j.AGCS.2020.20190026 Abstract （1032）   HTML （46）    PDF（pc） （654KB）（348）       Knowledge map    Save Related Articles | Metrics Select Study on acceleration approach for earth’s gravity field modelling based on satellite-to-satellite tracking technique WU Tangting Acta Geodaetica et Cartographica Sinica    2020, 49 (1): 134-134.   DOI: 10.11947/j.AGCS.2020.20190257 Abstract （747）   HTML （31）    PDF（pc） （656KB）（208）       Knowledge map    Save Related Articles | Metrics Select Geodesy discipline: progress and perspective YAO Yibin, YANG Yuanxi, SUN Heping, LI Jiancheng Acta Geodaetica et Cartographica Sinica    2020, 49 (10): 1243-1251.   DOI: 10.11947/j.AGCS.2020.20200358 Abstract （3120）   HTML （253）    PDF（pc） （1073KB）（2902）       Knowledge map    Save The geodesy discipline has been evolving and constantly intersecting and merging with other disciplines in the last 50 years, due to the continuous progress of geodetic observation techniques and the continuous expansion of application fields. The background and roles of the geodesy development are described in this paper at first, then the formations of the geodetic disciplines are sorted out as well. Furthermore, the basic growth of the geodesy subject is described from the progress of observation techniques, sensors and platforms, the cross-discipline formation is analyzed from the expansion of application fields. And the future development trends are analyzed from national requirements and science developments. The sub-disciplines for geodetic subject are suggested at present stage, based on the requirements of The National Natural Science Foundation of China and the development status of the geodesy, which may be referenced for geodetic scientific research topic selection and fund application. Reference | Related Articles | Metrics Select TH-2 satellite engineering design and implementation LOU Liangsheng, LIU Zhiming, ZHANG Hao, QIAN Fangming, HUANG Yan Acta Geodaetica et Cartographica Sinica    2020, 49 (10): 1252-1264.   DOI: 10.11947/j.AGCS.2020.20200175 Abstract （3278）   HTML （125）    PDF（pc） （5520KB）（2020）       Knowledge map    Save The TH-2 satellite system is China's first microwave surveying satellite system based on interferometric synthetic aperture radar technology, and is also China's first short-range formation satellite system. It is the second microwave interferometric surveying satellite system after the German's TanDEM-X system in the world. A method to solve the problem of absolute ambiguity in the interference phase by designing dual-frequency imaging is proposed for the first time in the world, which completely got rid of the dependence on ground control data. The system works in the X band, with the resolution of 3 m and a solar synchronous orbit of 500 km. It is composed of two equal satellites. It adopts a technical system of satellite formation in different orbits and a bistatic radar transceiver mode. It can measure the global digital surface models and acquire radar orthophotos in a short time. In this paper, through the selection of the interference baseline system, satellite formation configuration and radar transceiver mode, the technical system of TH-2 satellite is proposed. The engineering design is carried out from three aspects:system mission, main performance and composition. The implementation of the project is expounded from the three stages of the overall demonstration, the key technical research and verification, and project development. Finally, the on-orbit test and verification of the satellite system is introduced. Test results show that all indicators have reached the requirements of engineering design, products' precision is equivalent to TanDEM -X system and can meet the 1:50 000 scale mapping accuracy. These verify the TH-2 satellite' engineering design ideas correct and the method of project implementation reasonable and feasible. Reference | Related Articles | Metrics Select Expression and information hierarchical authorization of BDS reference station observation data based on states and residual ZHOU Letao, HUANG Dingfa, YUAN Linguo, FENG Wei, GONG Xiaoying, TIAN Yumiao, ZHANG Xi, ZHAO Yinghao Acta Geodaetica et Cartographica Sinica    2020, 49 (10): 1265-1274.   DOI: 10.11947/j.AGCS.2020.20190300 Abstract （1298）   HTML （37）    PDF（pc） （5239KB）（769）       Knowledge map    Save BDS reference stations typically store and transmit raw observations directly and make them available to users, which can lead to two disadvantages:first, there is no hierarchical authorization mechanism for users. Any user can solve the precise spatial, time and atmospheric datum information of the reference station through the original observation measurement, which poses a potential threat to the safety of the reference station, second, the strong correlation between the original observation measurement leads to a large amount of data, in BDS receiver observation appears network, uninterrupted, high sampling and multi-band trend, its observation data is a massive explosion, to the data storage and transmission have brought great pressure. Therefore, this paper proposes to use state and residual to express the raw observation data of BDS reference station. Compared with the common data services based on international protocols such as RINEX, Compact RINEX and RTCM, the advantage of this method is that it cannot only provide hierarchical authorization service of datum information for users, technically guarantee the security of data services, but also significantly reduce the amount of transmission data and user-side computation. At the same time, the new expression is equivalent to the original data and does not reduce the accuracy of the final calculation results. This method can be used to establish BDS observation data storage and transmission protocol with independent intellectual property rights, and provide technical support for satellite-based broadcasting services of high-precision data. Reference | Related Articles | Metrics Select Satellite precise orbit determination with ionospheric-free strategy using triple-frequency observations ZENG Tian, SUI Lifen, RUAN Rengui, JIA Xiaolin, FENG Laiping Acta Geodaetica et Cartographica Sinica    2020, 49 (10): 1275-1284.   DOI: 10.11947/j.AGCS.2020.20190325 Abstract （921）   HTML （25）    PDF（pc） （2123KB）（462）       Knowledge map    Save As the development of global navigation satellite system (GNSS), GNSS satellites transmitting multi-frequency signals has become a prevailing trend. However, recently the international GNSS service (IGS) analysis centers still use dual-frequency (DF) observations to derive the orbits, clocks and other products. The additional observations from the third frequency are not considered. We use two DF ionospheric-free (IF) combinations as the observation model, the improvements from the third frequency on orbits, clocks and station positions are assessed. In the carrier phase observation model, the satellite-dependent time-invariant and time-variant components are introduced. The two DF IF observation equations are re-parameterized to make the clock parameter aligned to the IGS clock products, and then the full-rank TF observation model is derived. Based on the strategy of building up extra wide lane, wide lane and narrow lane double-differenced ambiguities, the TF ambiguity resolution (AR) method is deduced. First taking 12 GPS Block IIF satellites as example, three precise orbit determination (POD) schemes, the L1/L2 DF IF POD (denoting as S1), the L1/L5 DF IF POD (denoting as S2), the L1/L2 and L1/L5 TF IF POD (denoting as S3), are processed in two station layouts. Results show that the S3 scheme in two station layouts can obtain the optimal precision. The orbit improvements of S3 with respect to S1 in cases of even and uneven distribution are within 10% and about 10%, respectively. The improvement of clocks RMS is slight, while STD is improved by 6.4% and 10.0%. The improved percentages of S3 vs. S2 are about less one times than that of S3 vs. S1, with the improved percentage of about 5%. Then the BDS-only POD test is processed and the orbits are validated by satellite laser ranging residuals. Results show that comparing with B1/B3 POD, the orbit and clock accuracy of TF POD can be improved. However, the improvement of TF POD comparing to B1/B2 POD is slight or even worse. The possible reason is the inaccuracy antenna phase values. Reference | Related Articles | Metrics Select The joint inversion of regional water reserve changes in the Qinghai-Tibet Plateau based on GRACE RL06 and TRMM data QIN Yikun, WANG Zegen, FAN Dongming Acta Geodaetica et Cartographica Sinica    2020, 49 (10): 1285-1294.   DOI: 10.11947/j.AGCS.2020.20200026 Abstract （1075）   HTML （36）    PDF（pc） （6714KB）（461）       Knowledge map    Save In the past decade, independent component analysis (ICA) has been gradually introduced into the component extraction of Earth's time-varying gravity field. Because of the independence of the extracted components, ICA solves the key problem that the extracted components are only irrelevant when using principal component analysis (PCA). The FastICA algorithm based on negative entropy is a common ICA method. The algorithm converges faster than the gradient algorithm, and the robustness of negative entropy is better. In this paper, the above algorithm is used to explore the relationship between the water storage components and precipitation components of the Qinghai-Tibet Plateau. The research indicates that there is a 7-month delay effect on the changes in water reserves on the Plateau compared to precipitation. It shows that in addition to seasonal frozen soils and glaciers, and the precipitation from the monsoon climate, there are also objective delays caused by regional water exchange. In view of the characteristic signals, the changes in annual average water reserves between central Qinghai, western Tibet, and central and eastern Tibet have reversed. It is pointed out that in the context of accelerated melting of frozen soil and glaciers caused by global warming, the regional water reserve changes due to different climate and flow regions. In addition, the changes of water reserves in the above areas are also different due to the north and south plate tectonics of the Qinghai-Tibet Plateau. Therefore, through the above studies, the feasibility of using the FastICA algorithm to analyze changes in regional water reserve components and their related factors on a large scale has been proven. Reference | Related Articles | Metrics Select Pixel extraction of reflected point source image for high spatial resolution optical remote sensing satellite XU Weiwei, ZHANG Liming, LI Xin, YANG Baoyun Acta Geodaetica et Cartographica Sinica    2020, 49 (10): 1295-1302.   DOI: 10.11947/j.AGCS.2020.20190246 Abstract （888）   HTML （32）    PDF（pc） （2376KB）（412）       Knowledge map    Save Pixel extraction accuracy is one of the key factors for geometric calibration accuracy of high resolution optical remote sensing satellites. A pixel extraction method is presented based on the light and small, automated reflected point source, which obtained pixel coordinates of point source image by parameterized Gaussian model fitting. The preliminary results show that the collinear error of pixel coordinates extracted by the reflected point source method is less than 0.001 pixels. The relative standard deviation of the proportional constant is also less than 5‰. And pixel coordinates extraction accuracy of point source image is less than 0.05 pixels comparing with common methods such as centroid method. The reflected point source can not only achieve high-precision pixel extraction, but also realize high-precision geometric calibration and image quality evaluation of high resolution optical remote sensing satellites, which is of great significance for improving the accuracy of China's space remote sensing stereo mapping. Reference | Related Articles | Metrics Select A S-RVoG model-based PolInSAR nonlinear complex least squares method for forest height inversion XIE Qinghua, ZHU Jianjun, WANG Changcheng, FU Haiqiang, ZHANG Bing Acta Geodaetica et Cartographica Sinica    2020, 49 (10): 1303-1310.   DOI: 10.11947/j.AGCS.2020.20190081 Abstract （1109）   HTML （14）    PDF（pc） （7611KB）（520）       Knowledge map    Save The classical three-stage forest height geomatical inversion method is easily affected by the assumption of the amplitude ratio of ground-to-volume scattering (GVR) and terrain slope. To address these problems, from the perspective of survey adjustment, the S-RVoG (slope-random volume over ground) based nonlinear complex least squares forest height inversion method is proposed in this paper. On the one hand, it does not need to hold the GVR assumption. On the other hand, it can take into account the terrain slope effect by adopting the S-RVoG model as the adjustment model. Three scenes of P-band PolInSAR data acquired from ESA BioSAR2008 campaign are used to construct two groups of single baseline tests for forest height inversion. The results show the RVoG-based nonlinear complex least squares method can obtain better forest height results than the three-stage geometrical method in a single baseline configuration. The proposed S-RVoG based nonlinear complex least squares method can further improve the accuracy. The improvement reaches a stand-level mean of 18.48% for slopes greater than 10°. Reference | Related Articles | Metrics Select Radiometric cross-calibration of GF-4 satellite PMS sensor considering the characteristics of multiple integration times HAN Jie, TAO Zui, XIE Yong, LIU Qiyue, SHI Hongbin Acta Geodaetica et Cartographica Sinica    2020, 49 (10): 1311-1320.   DOI: 10.11947/j.AGCS.2020.20200057 Abstract （992）   HTML （9）    PDF（pc） （3226KB）（415）       Knowledge map    Save Integrating the five integration times characteristics of GF-4 satellite PMS sensor,a radiometric cross-calibration method based on the radiometric block adjustment is proposed. Taking Dunhuang radiometric calibration sites (DRCS) in China as the radiometric transfer platform. Firstly, collecting the valid time-series MODIS images over DRCS to build the BRDF model. Secondly, considering the SBAF and BRDF, the radiometric control points (RCPs) are extracted from the image pairs of Landsat-8 OLI and PMS over DRCS. Thirdly, after setting the restrictive conditions of DN and CV, the radiometric tie points (RTPs) are extracted from PMS images in different integration times under the stare imaging condition. Finally, the radiometric cross-calibration coefficients of five integration times are solved based on the proposed method. The validation results show that the average absolute calibration relative errors of five integration times are all less than 5.18% and the relative radiometric correction errors of five integration times reduce up to 36.64%. Meanwhile, the influences of the RCPs distribution, the restrictive conditions in the process of RTPs extraction, SBAF and BRDF on the calibration results are discussed, which is beneficial to further optimize the radiometric cross-calibration program of PMS. Reference | Related Articles | Metrics Select A real-time analysis and visualization for area coverage of remote sensing satellite LU Wanjie, XU Qing, LAN Chaozhen, Lü Liang, ZHOU Yang Acta Geodaetica et Cartographica Sinica    2020, 49 (10): 1321-1330.   DOI: 10.11947/j.AGCS.2020.20190289 Abstract （1363）   HTML （53）    PDF（pc） （2872KB）（778）       Knowledge map    Save The increasing demands and diverse missions in earth observation lead to the complexity of satellite area coverage analysis, and satellite area coverage algorithms or applications cannot provide real-time response and online services that can handle high concurrent requests. Current analysis results cannot be visualized in real time, which increases the difficulty of data cognitive. To solve these problems, this paper proposes an efficient real-time analysis method and visualization service for satellite area coverage, which is combined with flow processing technology. First, a multi-mode judgment strategy is adopted to calculate the satellite area coverage parameters efficiently. Then, the continuous computing tasks are segmented to implement real-time data processing. Finally, based on streaming processing technology, this paper proposes an online service for real-time calculation and visualization. By using the data which contains three satellites and two ground areas to verify the algorithm, the experimental result shows that the method in this paper can not only ensure the accuracy under different sensor orientations, but can also greatly improve the computational efficiency. It can also provide real-time visualization of the analysis results in a timely and efficient manner. Reference | Related Articles | Metrics Select A Deep few-shot learning algorithm for hyperspectral image classification LIU Bing, ZUO Xibing, TAN Xiong, YU Anzhu, GUO Wenyue Acta Geodaetica et Cartographica Sinica    2020, 49 (10): 1331-1342.   DOI: 10.11947/j.AGCS.2020.20190486 Abstract （1062）   HTML （61）    PDF（pc） （2721KB）（723）       Knowledge map    Save For hyperspectral image classification problem of small sample, this paper proposes a depth of less sample learning algorithm, this algorithm through the simulation of the small sample classification in the process of training is to train the depth 3D convolution neural network feature extraction, the extraction of characteristic with smaller class span and large spacing between classes, more suitable for small sample classification problem, and can be used for different hyperspectral data, has better generalization ability. The trained model is used to extract the features of the target data set, and then the nearest neighbor classifier and support vector machine classifier are combined for supervised classification. Three groups of hyperspectral image data of Pavia university, Indian Pines and Salinas were used in the classification experiment. The experimental results showed that the algorithm could achieve a better classification accuracy than the traditional semi-supervised classification method under the condition of fewer training samples (only 5 marked samples were selected for each type of feature as training samples). Reference | Related Articles | Metrics Select A cloud and snow detection method of TH-1 image based on combined ResNet and DeepLabV3+ ZHENG Kai, LI Jiansheng, YANG Jianfeng, OUYANG Wen, WANG Gaojie, ZHANG Xun Acta Geodaetica et Cartographica Sinica    2020, 49 (10): 1343-1353.   DOI: 10.11947/j.AGCS.2020.20190420 Abstract （1476）   HTML （36）    PDF（pc） （5405KB）（1034）       Knowledge map    Save Cloud and snow detection is an important part of satellite remote sensing image processing, and also a key step for its following analysis and interpretation. In this paper, a simultaneous cloud and snow detection method for satellite remote sensing images based on ResNet and DeepLabV3+ fully convolutional neural network is proposed. The ResNet50 backbone is used, and the DeepLabV3+ network structure is optimized and improved according to the characteristics of cloud and snow on TH-1 remote sensing image. The ELU activation function, Adam gradient descent method and Focal Loss function are used to speed up convergence and improve segmentation accuracy. The network is trained and tested with the cloud and snow image dataset of TH-1 satellite. The experimental results show that it has strong robustness compared with Otsu method, and the detection accuracy of proposed method exceeds FCN-8s and original DeepLabV3+ network, meanwhile the detection speed of proposed method is faster than original DeepLabV3+, which can be applied to a variety of different remote sensing images through some adjustment and has favorable application prospects. Reference | Related Articles | Metrics Select The method of progressive typification for building groups with straight linear patterns GUO Qingsheng, LI Guoxian, WANG Yong, LIU Jiping, WEI Zhiwei Acta Geodaetica et Cartographica Sinica    2020, 49 (10): 1354-1364.   DOI: 10.11947/j.AGCS.2020.20190495 Abstract （1142）   HTML （35）    PDF（pc） （3021KB）（404）       Knowledge map    Save The pattern structure of buildings in the map generalization is a key factor to be considered. When there are spatial graphic conflicts among subgroups of buildings in different patterns, the generalization of these buildings becomes more complex. The generalization of straight linear pattern buildings is dominated by typification on large scale topographic maps. This paper proposes a progressive typification method for building subgroups of straight linear patterns with potential spatial graphic conflicts. The proposed method can progressively deal with the spatial graphic conflict between building subgroups in multiple straight linear patterns, and retain the important straight linear pattern structure of building groups. The position, shape, size and orientation of the typical building can be determined automatically with the restriction of visual graphical constraints expressed by the building. This paper also studies the automatic identification method of straight linear pattern of building subgroups based on the spatial proximity graph of building groups, and analyzes the adjacent relationship and intersection relationship between these straight linear patterns. Finally, the buildings on the 1:5000 map as a test data were generalized into 1:25 000 map, which verifies the availability and effectiveness of the algorithm proposed in this article. Reference | Related Articles | Metrics Select Design and optimization of spatial vector data storage model based on HBase XIE Peng, YANG Chuncheng, XIONG Shun, HE Liesong, ZHOU Xiaodong Acta Geodaetica et Cartographica Sinica    2020, 49 (10): 1365-1373.   DOI: 10.11947/j.AGCS.2020.20190525 Abstract （1079）   HTML （30）    PDF（pc） （3075KB）（664）       Knowledge map    Save Data storage model is an important part of database model. This paper aims at bottleneck problems in developing relational spatial database and using HBase to manage spatial vector data. Based on the analysis of relational spatial database storage model, the rules fortransforming the relational database storage mode into HBase storage mode are applied to spatial vector data management, a method of transforming spatial vector data relational storage schema into HBase storage schema is proposed, and a HBase storage model is designed for spatial vector data. The model is optimized and improved by using HBase's features such as entity nesting, denormalization and schemalessness.The experimental results show that the query efficiency of the storage model designed in this paper is better than that of the HBase-based spatial vector data storage model in the absence of auxiliary indexes. Reference | Related Articles | Metrics Select Boltzmann entropy for spatial information of images GAO Peichao Acta Geodaetica et Cartographica Sinica    2020, 49 (10): 1374-1374.   DOI: 10.11947/j.AGCS.2020.20190425 Abstract （916）   HTML （20）    PDF（pc） （754KB）（509）       Knowledge map    Save Related Articles | Metrics Select Research on theory and application of image translation between SAR and optical Image QIN Yong Acta Geodaetica et Cartographica Sinica    2020, 49 (10): 1375-1375.   DOI: 10.11947/j.AGCS.2020.20190428 Abstract （706）   HTML （25）    PDF（pc） （776KB）（366）       Knowledge map    Save Related Articles | Metrics Select Filtering algorithms and reliability analysis for GNSS/INS integrated navigation systems JIANG Chen Acta Geodaetica et Cartographica Sinica    2020, 49 (10): 1376-1376.   DOI: 10.11947/j.AGCS.2020.20190429 Abstract （644）   HTML （44）    PDF（pc） （768KB）（579）       Knowledge map    Save Related Articles | Metrics