Acta Geodaetica et Cartographica Sinica

Geodesy discipline: progress and perspective

YAO Yibin, YANG Yuanxi, SUN Heping, LI Jiancheng

2020, 49(10): 1243-1251. doi:10.11947/j.AGCS.2020.20200358

Asbtract ( )

HTML ( )

PDF (1073KB) ( )

References | Related Articles | Metrics

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.

TH-2 satellite engineering design and implementation

LOU Liangsheng, LIU Zhiming, ZHANG Hao, QIAN Fangming, HUANG Yan

2020, 49(10): 1252-1264. doi:10.11947/j.AGCS.2020.20200175

Asbtract ( )

HTML ( )

PDF (5520KB) ( )

References | Related Articles | Metrics

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.

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

2020, 49(10): 1265-1274. doi:10.11947/j.AGCS.2020.20190300

Asbtract ( )

HTML ( )

PDF (5239KB) ( )

References | Related Articles | Metrics

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.

Satellite precise orbit determination with ionospheric-free strategy using triple-frequency observations

ZENG Tian, SUI Lifen, RUAN Rengui, JIA Xiaolin, FENG Laiping

2020, 49(10): 1275-1284. doi:10.11947/j.AGCS.2020.20190325

Asbtract ( )

HTML ( )

PDF (2123KB) ( )

References | Related Articles | Metrics

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.

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

2020, 49(10): 1285-1294. doi:10.11947/j.AGCS.2020.20200026

Asbtract ( )

HTML ( )

PDF (6714KB) ( )

References | Related Articles | Metrics

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.

Pixel extraction of reflected point source image for high spatial resolution optical remote sensing satellite

XU Weiwei, ZHANG Liming, LI Xin, YANG Baoyun

2020, 49(10): 1295-1302. doi:10.11947/j.AGCS.2020.20190246

Asbtract ( )

HTML ( )

PDF (2376KB) ( )

References | Related Articles | Metrics

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.

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

2020, 49(10): 1303-1310. doi:10.11947/j.AGCS.2020.20190081

Asbtract ( )

HTML ( )

PDF (7611KB) ( )

References | Related Articles | Metrics

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°.

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

2020, 49(10): 1311-1320. doi:10.11947/j.AGCS.2020.20200057

Asbtract ( )

HTML ( )

PDF (3226KB) ( )

References | Related Articles | Metrics

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.

A real-time analysis and visualization for area coverage of remote sensing satellite

LU Wanjie, XU Qing, LAN Chaozhen, Lü Liang, ZHOU Yang

2020, 49(10): 1321-1330. doi:10.11947/j.AGCS.2020.20190289

Asbtract ( )

HTML ( )

PDF (2872KB) ( )

References | Related Articles | Metrics

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.

A Deep few-shot learning algorithm for hyperspectral image classification

LIU Bing, ZUO Xibing, TAN Xiong, YU Anzhu, GUO Wenyue

2020, 49(10): 1331-1342. doi:10.11947/j.AGCS.2020.20190486

Asbtract ( )

HTML ( )

PDF (2721KB) ( )

References | Related Articles | Metrics

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).

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

2020, 49(10): 1343-1353. doi:10.11947/j.AGCS.2020.20190420

Asbtract ( )

HTML ( )

PDF (5405KB) ( )

References | Related Articles | Metrics

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.

The method of progressive typification for building groups with straight linear patterns

GUO Qingsheng, LI Guoxian, WANG Yong, LIU Jiping, WEI Zhiwei

2020, 49(10): 1354-1364. doi:10.11947/j.AGCS.2020.20190495

Asbtract ( )

HTML ( )

PDF (3021KB) ( )

References | Related Articles | Metrics

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.

Design and optimization of spatial vector data storage model based on HBase

XIE Peng, YANG Chuncheng, XIONG Shun, HE Liesong, ZHOU Xiaodong

2020, 49(10): 1365-1373. doi:10.11947/j.AGCS.2020.20190525

Asbtract ( )

HTML ( )

PDF (3075KB) ( )

References | Related Articles | Metrics

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.

Boltzmann entropy for spatial information of images

GAO Peichao

2020, 49(10): 1374-1374. doi:10.11947/j.AGCS.2020.20190425

Asbtract ( )

HTML ( )

PDF (754KB) ( )

Table of Content