Table of Content

25 February 2023, Volume 0 Issue 2

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Temporal and spatial changes of eco-environmental quality and its influencing factors in the Dongting Lake basin from 2001 to 2019

ZHANG Rui, LIU Xiuguo, XU Dong, LI Qin, SUI Bing, CHEN Leishi

2023, 0(2):  1-8.  doi:10.13474/j.cnki.11-2246.2023.0032

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In recent years, the ecological environment of the Dongting Lake basin has been under great pressure due to natural disasters, unreasonable exploitation and utilization. Accurate and real-time acquisition of temporal and spatial pattern and evolution trend of eco-environmental quality is of great significance for eco-environmental protection and construction in the Dongting Lake basin. In view of the ecological situation of the Dongting Lake basin with rich vegetation and biodiversity, based on CHEQ using standardized coefficient multiple linear regression method and random forest algorithm, this study explores the temporal and spatial evolution characteristics of eco-environmental quality in the Dongting Lake basin and the influence of social and natural factors on the ecology of the Dongting Lake basin. The results show that: ① The eco-environmental quality of the Dongting Lake basin decreased rapidly from 2001 to 2009, and increased slowly from 2010 to 2019. The average trend rate of CHEQ was -0.17×10^-3 a^-1, indicating that the eco-environmental quality of Dongting Lake basin showed a decreasing trend during the past 19 years. In the past 19 years, 20.31% of the areas where the eco-environmental quality has been improved significantly in the Dongting Lake basin, while degraded seriously areas accounted for 24.33%. ② During the study period, Pingjiang county, Taoyuan county and Taojiang county ranked the top three in ecological environmental quality, and the ecological quality was basically in good grade. Furong district, which ranked at the bottom of ecological quality, degraded from a poor grade to a terrible grade. ③ From the perspective of time, the main driving factors of eco-environmental quality change in the Dongting Lake basin were water shortage and IBI index in the past 19 years. The driving factors for the spatial distribution of eco-environmental quality in the Dongting Lake basin were temperature, soil moisture, surface runoff and IBI index. Henceforth, the management strategy of the Dongting Lake basin should focus on ecological restoration, promote the coupling and coordinated development of economy and ecology, and develop industrial groups that adapt to the ecological environment of the basin as the main goal, so as to realize the sustainable utilization of ecological resources in the basin. This study can provide a scientific basis for exploring the coordinated method of sustainable utilization and practical protection of natural resources in the Dongting Lake basin.

Analysis of spatial-temporal dynamic change characteristics of wetland water body in arid basin based on GEE:a case study of Ningxia plain

ZOU Yebin, CHAI Mingtang, YANG Juan, SHEN Xiaojing, FENG Dongpu, SHU Rui

2023, 0(2):  9-14.  doi:10.13474/j.cnki.11-2246.2023.0033

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Ecological conservation and high-quality development of the Yellow River Basin has become a major national strategy. NingXia plan is a representative wetland area in the arid region. Based on the google earth engine platform, the dynamic information such as historical coverage, area change, type change and seasonal evolution of wetland water bodies in the Ningxia plain from 1984 to 2020 was analyzed and evaluated. The results show that: ① From 1984 to 2020, the historical coverage area of wetlands in the Ningxia plain was 1 373.86 km², accounting for 8.1% of the national land area of the study area, and the area covered by water body in the whole period was 116.46 km². ② From 1984-1999 to 2000-2020, the surface water area of the Ningxia plain increased by 483 km², and the overall area change rate was 45.6%. ③ In the past 37 years, the newly added permanent water bodies in the study area have increased significantly by 218.89 km², and the seasonal water body area has changed greatly. ④ In terms of the number of months covered by surface water, in 2020, 39.45% of the water bodies persisted throughout the year, while the area of water bodies covered by 1 to 6 months accounted for more than 50% of the total. The research can provide date support for environmental protection and high-quality development of the Yellow River Basin.

Temporal and spatial variation of vegetation net primary product and its response to hydrothermal conditions and grain for green project in the Yellow River basin

XIE Yanling, XIA Zhengqing, WANG Tao, ZHANG Zhengliang, ZHU Dongchun

2023, 0(2):  15-20.  doi:10.13474/j.cnki.11-2246.2023.0034

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On the basis of MOD17A3HGF vegetation primary productivity (NPP) data, as well as the air temperature, precipitation and DEM data, the temporal and spatial change characteristics of vegetation NPP in the Yellow River basin from 2000 to 2020 and its response to hydrothermal and grain for green project (GGP) is carried out. The results show that: ① the overall trend of vegetation NPP in the Yellow River basin shows a significant linear increase (P<0.001), and the growth rate of vegetation NPP in the middle reaches is higher than that in the lower reaches, and the lower reaches is higher than the upper reaches. The vegetation NPP in the Yellow River basin increase significantly, accounting for 95.29%, which is concentrate in the middle reaches (the Loess Plateau region), while the significantly decrease areas are mainly concentrated in densely populated urban areas. ② The vegetation NPP in the Yellow River basin is mainly positively correlated with the annual average air temperature and annual precipitation, of which the significant positive correlations account for 11.15% and 42.35%, respectively, and which distribute in east-west and south-north direction, respectively. ③ The growth of vegetation NPP in the slope of [15°,25°] region is the fastest, followed by the >25° and <15° regions. It reflects the vegetation improvement effect of the grain for green project on the Loess Plateau in the middle reaches of the Yellow River basin.

Temporal and spatial variation characteristics of coupling coordination degree between urbanization and ecological environment of urban agglomeration in the Yangtze River Delta during 2001-2018

XU Youqin, ZHU Guangxiang, LI Xiaopeng, ZHAO Wenqing, XU Dong

2023, 0(2):  21-27.  doi:10.13474/j.cnki.11-2246.2023.0035

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The development of urbanization is closely related to the ecological environment. The dynamic monitoring and analysis of the coupling coordination degree of urbanization and ecological quality can be accurately carried out by using remote sensing method, so as to provide necessary reference basis for regional urbanization construction, ecological governance and development planning. Taking the Yangtze River Delta urban agglomeration as an example, this paper uses Landsat series data and DMSP/OLS night light data to establish the remote sensing ecological index (RSEI) and the light index (CNLI) representing the regional ecological environment respectively. Using the coupling coordination degree model to monitor and analyze the change of the coupling coordination degree of urbanization and ecological environment of the Yangtze River Delta urban agglomeration from 2001 to 2018 in this paper. The results show that: ① from 2001 to 2018, the urbanization level of urban agglomeration in the Yangtze River Delta continued to improve, and the urbanization index increased from 0.112 in 2001 to 0.288 in 2018. ② From 2001 to 2018, the eco-environmental quality of urban agglomerations in the Yangtze River Delta was declining, and the regions with excellent ecological grade were shrinking, especially in Shanghai and Nanjing division. ③ From 2001 to 2018, the coordination degree of urbanization and ecological environment of cities in the Yangtze River Delta urban agglomeration generally showed an upward trend, and the coordination degree of urbanization and ecological environment of cities varied greatly in space.

Eco-environmental quality assessment and driving force analysis based on RSEI: a case study of the Minjiang River basin (Fuzhou section)

SHI Zhiyong, HU Xiaoting, XIE Huili, LIU Xingzhao

2023, 0(2):  28-33.  doi:10.13474/j.cnki.11-2246.2023.0036

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Ecological environment is very important to the sustainable development of social economy. In order to study the changes of ecological environment in the Minjiang River basin (Fuzhou section), based on the remote sensing images in 2010, 2015 and 2021, remote sensing based ecological index (RSEI) is constructed by principal component analysis to evaluate and monitor the ecological environment quality of the Minjiang River basin (Fuzhou section) in recent 12 years. And the reason of its change is analyzed with geographic detector. The results showed that: ① RSEI index of the Minjiang River basin (Fuzhou section) in 2010, 2015 and 2021 is 0.62, 0.70 and 0.68, respectively. ② RSEI index of most regions is good and excellent. The area of ecological improvement is greater than the area of ecological deterioration, and the overall ecological environment is developing in a good way. ③ Dryness and heat are the key driving factors of ecological environment quality.

Elevation error checking of stereo mapping satellite based on LoFTR and adaptive IRLS

GUO Haoyu, LIU Qiang, WAN Yi

2023, 0(2):  34-39.  doi:10.13474/j.cnki.11-2246.2023.0037

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The mapping accuracy of stereoscopic surveying and mapping satellite is affected by many factors. Quality of the surveying and mapping products can be effectively ensured by adopting precise and comprehensive measurements of the plane elevation error on the butt side of the stereoscopic images using certain technical means, while possible image distortions and anomalies inside can be filtered. In this paper, a method for checking the elevation edge error of stereo mapping satellites is proposed. Firstly, a large number of high-precision matching points can be obtained by feature matching of overlapping out-of-orbit stereo satellite image pairs through LoFTR, and screen for the matching point of forward intersection simultaneously. Figure out the elevation edge error of this position. Then, use the adaptive IRLS method to robustly estimate the average value of the elevation edge difference corresponding to the matching point in a single area. Finally, the reliable result can be obtained by screening out the inspection result outliers. By evaluating the experiment results of the ZY-3 and Gaofen-7 stereo pair, it is proved that the accuracy level achieved by the method is sufficient to meet the accuracy requirements of the elevation error inspection of stereo mapping satellites, and the effectiveness of the method has been validated too.

Cross-view image geolocalization combining category filtering and reranking

LI Ziyu, ZHOU Weixun, GENG Wanxuan

2023, 0(2):  40-45.  doi:10.13474/j.cnki.11-2246.2023.0038

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To solve the problem that cross-view images have great viewpoint difference and thus resulting in low geolocalization accuracy, this paper takes Siamese network as the basic structure and proposes a localization method based on similarity learning and scene category filtering, as well as reranking. Firstly, the cross-view images are used for similarity learning, and the reference remote sensing images are sorted according to the similarity values. Then, the categories of ground-view and remote sensing images are obtained by training SVM classifier. Finally, geolocalization is performed using feature similarity and scene category information, as well as reranking. The experimental results show that the proposed method can improve geolocalization performance compared to conventional feature matching-based methods. Moreover, the results also demonstrate the effectiveness of scene category filtering and reranking for geolocalization.

A downhole localization algorithms incorporating improved wavelet denoising and T-Taylor

HU Rongming, SU Ruipeng, JING Xia, MI Xiaomei, ZHENG Jiangle

2023, 0(2):  46-51.  doi:10.13474/j.cnki.11-2246.2023.0039

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A downhole localisation algorithm that incorporates improved wavelet denoising and the T-Taylor algorithm is proposed to address the problem that the signal is susceptible to non line of sight (NLOS) errors in the ultra wide band downhole localisation method, resulting in poor accuracy and environmental adaptability of the localisation algorithm. Noise reduction is applied to the original range values to suppress the influence of NLOS errors on localisation, while the three-ball rendezvous algorithm is introduced as the initial algorithm of the Taylor algorithm to ensure the convergence of the Taylor algorithm while enhancing the localisation accuracy and environmental adaptability of the localisation algorithm in complex downhole environments. The results show that the fusion algorithm can reduce the ranging error to a certain extent, enhance the adaptability of the algorithm to the complex environment, improve the positioning accuracy, and have higher positioning accuracy and noise immunity than the C-Taylor algorithm in the NLOS environment. The average positioning accuracy of the fusion algorithm is improved by 37.3% compared to the C-Taylor algorithm, as verified by field positioning experiments.

Combined time series coherence and backscattering coefficient for wetland classification in the Yellow River Delta

LI Zhenjin, WANG Zhiyong, YE Kaile, LIU Xiaotong, TIAN Kang

2023, 0(2):  52-57,71.  doi:10.13474/j.cnki.11-2246.2023.0040

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To solve the problem that the backscattering coefficient is difficult to complete the high-precision wetland classification, this paper takes 16 VH Sentinel-1A images as the data source, and constructs a classification method combining time series coherence and backscattering coefficient. By analyzing the long time series backscattering coefficient and coherence, the backscattering coefficients map in three times (June 27 (R), November 18 (G) and November 30 (B)) that Spartina alterniflora is easily confused with other ground objects are selected as the synthetic data sources. Then the coherence map from November 18 to November 30 is introduced to replace the backscattering coefficients map in November 18. SVM and RF classifier are used to explore the accuracy variation before and after introducing coherence in the Yellow River Delta wetlands. The results show that the overall accuracy of classification results by SVM and RF improves by 3.07% and 3.85%, and the accuracy of Spartina alterniflora improves by 9.39% and 11.42%.

Wetland plant community classification based on Relief F and convolutional neural network

ZHANG Yongbin, LIU Yahui, LIU Mingyue, MAN Weidong, SONG Tanglei, LI Chunyu

2023, 0(2):  58-64.  doi:10.13474/j.cnki.11-2246.2023.0041

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Wetland is an important transition zone between terrestrial and aquatic ecosystems. Accurate and efficient acquisition of wetland plant community distribution information is of profound significance for wetland conservation. We use the UAV multispectral images as the data source, construct a multidimensional feature dataset containing spectral features, vegetation indices, and texture features, and determine the optimal feature dataset by the Relief F algorithm. Then, we construct a convolutional neural networks (CNN) classification model based on the feature selection and classify the optimal feature dataset with the CNN based on the original multispectral images. The results show that:① The classification accuracy increases and then decreases as the number of features increases, and the classification accuracy is highest when the number of features is 32. ② Texture features such as information entropy, homogeneity, and multispectral vegetation indices such as GNDVI, MSAVI2, and RVI extracted by GLCM with a window of 13×13 have higher importance. ③ The CNN classification model based on the optimal feature dataset can effectively extract the spatial-spectral information and suppress the “salt-and-pepper noise”, with the best classification effect and the overall accuracy of 93.40%, which is 9.80% and 7.40% higher than the RF and CNN classification models without feature optimization, respectively.

Automatic extraction of four-side trees based on fusion of spatial information and hyperspectral image

YU Haoyang, DONG Chun, ZHANG Hui

2023, 0(2):  65-71.  doi:10.13474/j.cnki.11-2246.2023.0042

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Four-side trees are an important part of forest coverage calculation. However, due to its sporadic distribution, the current statistical method is still a field research method with long statistical time and high calculation cost, and there is a lack of research on the use of remote sensing images and automatic extraction. Therefore, this paper takes the multi band Sentinel-2 remote sensing image as the data source for screening, combination and classification. It combines the definition of four-side tree and spatial analysis method to realize the automatic extraction of four-side tree. The experimental results show that the overall accuracy of the classification results of remote sensing images combined with 9, 6, 4 bands by using the support vector machine method of radial basis kernel function is 93.673 5%, the Kappa coefficient is 0.918 1, and the extraction accuracy of four side tree is 90%. The experimental accuracy is the highest. Compared with the field investigation method, this extraction method has high precision and faster speed, and is more suitable for a wide range of four-side tree information extraction and change detection.

A differential evolution BM3D hard threshold parameter denoising method for remote sensing images

HU Pengcheng, TANG Shihua, ZHANG Yan, LIU Kunzhi, Lü Fuqiang, LI Haoyang

2023, 0(2):  72-77.  doi:10.13474/j.cnki.11-2246.2023.0043

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Aiming at the problem of denoising of Gaussian white noise in remote sensing images, a differential evolution (DE) algorithm is used to optimize the hard threshold transformation parameters in the 3D block matching (BM3D) algorithm, which includes the block distance threshold and the 3D transformation domain hard threshold parameter, and then the optimized BM3D algorithm is used to eliminate Gaussian white noise in the image. Taking peak signal-to-noise ratio (PSNR), structural similarity (SSIM) and edge preservation index (EPI) as the evaluation indicators, the experimental results show that the fusion algorithm has better performance in PSNR, SSIM and EPI under different noise densities, especially the EPI has increased by about 2%. On the whole, the denoising effect of the remote sensing image Gaussian white noise of the fusion algorithm is better than that of the single BM3D denoising algorithm.

An improved block dense matching method based on depth map

WANG Yan, ZHANG Tingting, WANG Fei, LIU Zhendong

2023, 0(2):  78-83.  doi:10.13474/j.cnki.11-2246.2023.0044

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Oblique photography modeling often requires hundreds or even tens of thousands of images and usually requires block dense matching reconstruction. However, the commonly used block dense matching method can only model each block separately and the repeated images between blocks will participate in the matching calculation multiple times, resulting in redundancy and time-consuming calculations. Therefore, an improved block dense matching method is proposed. First, the image association algorithm is used to calculate the neighborhood image set for each image in the scene and the reconstruction state object of the image is initialized at the same time. Then, the entire scene is automatically clustered in space to complete the block and the sub-blocks needed for reconstruction are extracted. Finally, according to the image reconstruction state, object estimation, filtering depth map and depth map fusion generate dense point cloud. Experimental results show that this method can significantly improve the efficiency of oblique image 3D reconstruction.

Quarry recognition based on improved CycleMLP from high-resolution remote sensing imagery

ZHAO Yubin, NI Huan, NIU Xiaonan

2023, 0(2):  84-90.  doi:10.13474/j.cnki.11-2246.2023.0045

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The ecological restoration of the quarry area is an important link to improve the function of the regional ecosystem. Identifying the quarry and determining the boundary of the mining area are the prerequisites for completing the restoration task. Currently, the semantic segmentation technology based on deep learning can accurately recognize the objects of interest in high-resolution remote sensing images, providing an effective way for quarry identification. Based on the CycleMLP framework, this paper uses the pyramid structure to input multi-level features into a lightweight MLP decoder, aggregates feature information from different levels, and obtains local and global features at the same time. The convolutional layers are embedded into the feed-forward network, which avoids the accuracy decline caused by position-encoded interpolation. Experiments employ the semantic segmentation dataset of the quarry areas in Nan'an city, Fujian province to train the network and verify the accuracy. The results show that the improved CycleMLP can effectively identify quarry areas from high-resolution remote sensing images. Compared with other methods based on self-attention mechanism, the improved CycleMLP achieves higher accuracy, accurately extracts the boundary of the quarry area, and can provide reliable supporting materials for the restoration of the ecosystem in the quarry area.

An improved AKAZE algorithm for UAV image feature matching in debris flow area

ZONG Huilin, YUAN Xiping, GAN Shu, ZHANG Xiaolun, LIANG Changxian, ZHAO Zhenfeng

2023, 0(2):  91-96,103.  doi:10.13474/j.cnki.11-2246.2023.0046

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To solve the problem of low timeliness when UAV high-resolution image feature matching is used in debris flow disasters, an improved AKAZE UAV image feature matching algorithm is proposed in this paper. The AKAZE feature point detection algorithm is used to extract locally stable invariant features, and the binary descriptor BEBLID is used to describe the detected feature points. Then, the nearest neighbor distance ratio (NNDR) is used for preliminary matching. Furthermore, epipolar geometric constraint is used to calculate the transformation matrix to purify the inner points and improve matching quality. Five groups of UAV sequences images are selected for the feature-matching experiment and compared with the classic SIFT algorithm, AKAZE algorithm, and ORB algorithm. The experimental results show that the matching accuracy of the proposed method is close to that of SIFT algorithm, slightly higher than that of the AKAZE algorithm, significantly better than that of the ORB algorithm, and the calculation speed is significantly better than that of SIFT algorithm and AKAZE algorithm, basically reaching the calculation efficiency of ORB algorithm. The method proposed in this paper can be applied to the UAV image data processing in the debris flow scenes which requires high matching accuracy and matching time.

Identification of hidden dangers of landslides in UHV transmission channels in the Three Gorges Reservoir Area based on time series InSAR

ZHANG Lingqi, XIE Chou, CHEN Mi, TIAN Bangsen, YANG Zhi, ZHU Yu

2023, 0(2):  97-103.  doi:10.13474/j.cnki.11-2246.2023.0047

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The ultra high voltage(UHV) transmission line located in the Three Gorges Reservoir Area is an important part of China's power supply, but geological disasters such as landslides in the Three Gorges Reservoir Area occur frequently, which seriously threaten the safety of UHV transmission line. Therefore, the monitoring and identification of landslides are particularly important for the safe operation of UHV transmission lines. Due to the complex terrain and climate conditions in the Three Gorges Reservoir Area, this paper proposes an adaptive optimization network construction method and applies it to the process of time series interferometric synthetic aperture radar (InSAR) technology, and 84 Sentinel-1 images from Wanzhou-Badong in the Three Gorges Reservoir Area are processed to achieve surface deformation monitoring of UHV transmission channels. The reliability of the time series InSAR monitoring results are verified by the measurement data of the BeiDou Navigation Satellite System and the field investigation data of the Jinjiling landslide. According to the time series InSAR measurements, 8 obvious landslide hazards are identified in the UHV transmission channel. Further analysis of the time series deformation of the monitored Jinjiling landslide shows that the deformation characteristics of the landslide are related to rainfall, reservoir water level and engineering disturbance.

Monitoring 3D displacements of open-pit mine with InSAR by incorporating an aspect constraint

QIAN Yuyang, YANG Zefa, WU Lixin, ZHOU Yi, QIN Yuanjun

2023, 0(2):  104-109.  doi:10.13474/j.cnki.11-2246.2023.0048

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Since the accuracy of the solved north-south displacements with the traditional method of fusing multi-track InSAR observations is quite poor, it is challenging to scientifically identify the risks of geohazards of open-pit mine slopes. To circumvent this, we propose a new method to monitor three-dimensional displacements of open-pit mine slopes with multi-track InSAR by incorporating an aspect constraint in this paper. Firstly, a prior constraint is constructed based on the prior knowledge that the slope in open-pit mine horizontally moves towards the aspect direction in theory. Then, a functional model involving the prior constraint and three-dimensional displacements of open-pit mine slope is created, according to the projection of three-dimensional displacements onto SAR line of sight direction. Thirdly, three-dimensional displacements of open-pit mine slopes are solved based on the function model. The proposed method is tested in Xinqiu open-pit mine area, in China, and the results show that the accuracy of three-dimensional displacements is about 1.2 cm, occupying 5.6% of the maximum displacement. The proposed method is beneficial to improve the accuracy of InSAR-based three-dimensional displacements of open-pit mine, and further to enhance the ability to identify potential landslides in open-pit mine slope.

Spatio-temporal variations of land surface albedo and its driving factors over the Karst mountains area

HU Haitao, LIU Suihua

2023, 0(2):  110-116.  doi:10.13474/j.cnki.11-2246.2023.0049

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In order to understand the climatic effects of surface albedo in humid karst mountainous areas under the background of global warming, the author takes Guizhou province as an example in this thesis. MODIS surface albedo products, combined with data on vegetation, land use, geological lithology and other data are used. The temporal and spatial variation characteristics of surface albedo in Guizhou province in the recent 20 years are analyzed based on Theil-Sen Median slope calculation and Mann-Kendall statistical test. Geographical detector is used to analyze the dominant drivering factors of surface albedo in Guizhou. The results show that: ① The average surface albedo of Guizhou province from 2001 to 2020 is 0.111 0, and it is slowly fluctuating and decreasing at an annual average rate of 0.16×10^-3, with the area of decreasing area accounting for 58.17% of the total area. ② The annual average albedo is summer (0.118 6)>autumn (0.113 7)>spring (0.105 0)>winter (0.103 0), and the annual average growth rate is summer (0.48×10^-3)>autumn (-0.13×10^-3)>spring (-0.31×10^-3)>winter(-0.51×10^-3). ③ The annual variation of the surface albedo is inverted U-shaped, showing remarkable seasonal characteristics. ④ Vegetation, land use, and lithology combination are the dominant driving factors of the spatial-temporal heterogeneity of surface albedo in Guizhou. The interaction between these factors on surface albedo is the dual-factor enhancement or nonlinear enhancement.

Design of composite-symbol representation for landmark buildings

QIU Yuhong, TI Peng

2023, 0(2):  117-123.  doi:10.13474/j.cnki.11-2246.2023.0050

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In order to comprehensively reflect the visual and functional characteristics of landmark buildings on the map, a representation design method of composite-symbols for landmark buildings is proposed in this study. Landmark symbols are decomposed into two types of morphemes including building contour characteristics, function and functional status of landmark buildings, morphemes representations are designed respectively. Two operators including jointing and superimposing are used to generate composite landmark symbols based on morphemes. Experiment results show that the meaning of morphemes in the combined landmark symbols are easy to understand, and the combined form can be well accepted for the participants involved in this experiment, which proves the effectiveness of the method proposed in this study.

Design and application of cross-regional BDS service model in the Yangtze River Delta

SHEN Zhengzhong, FENG Yangmin, HU Zhengwei, YANG Zijian, LIU Li, WANG Kaishi

2023, 0(2):  124-127,149.  doi:10.13474/j.cnki.11-2246.2023.0051

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In order to realize the interconnection and interoperability of the satellite navigation and positioning reference service in the Yangtze River Delta, integrate the resource of BDS augmentation system in three provinces and one municipality, improve BDS service in support capability.This paper studies the technology of lightweight lazy grid and geofencing, designs a unified cross-region differential data format, proposes a regional integrated BDS application service model. ZJCORS service is released by “E-government-cloud”, which verifies the efficiency, and take an example of cross-regional operation in the west bank of Taihu lake to verifie the effectiveness of the service.

Investigation on low-cost remote ocean pseudorange differential positioning with BeiDou short message service

DONG Lin, JI Shengyue, WANG Zhenjie

2023, 0(2):  128-133,149.  doi:10.13474/j.cnki.11-2246.2023.0052

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Due to limitations of communication distance, pseudorange differential positioning technique can only be used in most of land areas or inshore ocean areas and cannot be used in remote ocean regions as the traditional communication wireless network, such as Wi-Fi or GPRS are not available, while satellite communication is the only communication means and it is too expensive to be afforded by ordinary users. Short message service of BeiDou satellite navigation system is one feature and it becomes another choice for data transmission due to its cheap price. In this research, pseudorange differential positioning technique based on BeiDou short message service is investigated and a method combining space-relative and time-relative positioning techniques is proposed. The simplifying and encoding measures of transmission data related to pseudo-range corrections are also discussed. Finally, based on practical ocean GNSS observations, performance of pseudorange differential positioning technique is tested with a distance about 1700 km from the rover to the reference station. The numerical test results show that the positioning errors are basically within 1 meter in horizontal directions and 2 meters in vertical direction. As the annual communication fee is only about 800 Chinese Yuan, the proposed method in this research can meet ocean need of many applications.

Building extraction method from remote sensing image based on foreground perception

SHI Zhongtian, SHEN Zhengwei, YANG Sihai

2023, 0(2):  134-138.  doi:10.13474/j.cnki.11-2246.2023.0053

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Building is the main feature of urban construction, is one of the basic elements of a city, is an important embodiment of the continuous development of urbanization, is the main place of human production and life. Therefore, how to effectively manage and supervise buildings is crucial. With the improvement of remote sensing image acquisition capability and widely spread applications, how to quickly and accurately extract buildings to provide a basis for subsequent applications become an urgent problem to be solved. In this paper, a method of building extraction by using remote sensing images based on foreground-aware is proposed by analyzing and combining advanced technologies such as depth learning. Firstly, the basic features are extracted by employing the improved ResNet from the input remote sensing image. Then, the pyramid feature map is obtained by using two-way FPN; the construction of relevant context association is achieved with the using of the foreground and geospatial scene modelling. After that, the input feature map is enhanced and the gap between foreground features and background features is enlarged, thus the foreground feature differentiation is improved. Finally, the efficient and accurate automatic extraction of buildings from remote sensing image is realized.

A Handheld 3D mapping technology based on hemispherical laser scanner SLAM approach

YANG Honggang

2023, 0(2):  139-144.  doi:10.13474/j.cnki.11-2246.2023.0054

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In order to solve the problem of rapid 3D mapping for indoor and outdoor scenes, a hemispherical laser scanner based simultaneous localization and mapping (SLAM) method is proposed, and a handheld portable 3D laser scanning system integrating hemispherical angle laser scanner and inertial measurement unit(IMU) is designed. Firstly, a ground point cloud segmentation algorithm is proposed to reduce the redundant vertical constraints according to the scanning line structural characteristics of the hemispherical laser scanner. Secondly, a tightly coupled iterative extended Kalman filter (IEKF) is presented to determine the position and attitude with the IMU and the down sampled point cloud. Finally, the incremental back-end optimization processing of factor map is used to eliminate the cumulative error and improve the accuracy of point cloud map. The prototype system developed with the proposed method is implemented to build 3D point cloud maps of typical indoor and outdoor scenes. The results show that the absolute positioning accuracy of this method is better than 4‰ and the relative positioning accuracy is better than 0.3‰. It has broad application prospects in indoor and outdoor integrated 3D mapping.

Intertidal zone measurement combined shipborne single beam bathymetry with airborne LiDAR system

ZHU Xiaowu, WANG Bin, LIU Jincang, HUANG Xiaochuan

2023, 0(2):  145-149.  doi:10.13474/j.cnki.11-2246.2023.0055

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Intertidal topographic surveys have a fundamental role in the protection and utilization of tidal flats. A combined shipborne single beam bathymetry echo measurement and airborne laser LiDAR integrated system is proposed. Firstly, the ODOM MKⅢ dual-frequency single beam bathymetry is used to collect and verify the accuracy of the point cloud results in the intertidal zone of the UAV airborne LiDAR. Then the key indicators for the implementation of UAV airborne LiDAR low-tide aerial photography are designed in complex environments. Finally the intertidal zone with high precision is optimized by combining the land topography of airborne LiDAR tidal flats at low tide and the underwater terrain of tidal flats with shipborne single beam bathymetry at high tide. Scale topographic map surveying method. The practice shows that: ① 816 measuring points in the overlapping area are selected to compare the two measurement accuracies, and 99% of the compared points have the difference in elevation within 0.2 m, indicating that the airborne laser LiDAR measurement can meet the measurement requirements of coastal tidal flats.② The UAV entering and leaving the survey area should be rotated in turn, and the horizontal flight combined with the figure-of-eight flight should be used to avoid the accumulation of IMU errors.③ The measurement system is of reference significance for the promotion of high-precision large-area topographic surveying projects in the intertidal zone.

Research and application an intelligent extraction platform of remote sensing image change detection

WANG Benli, WANG Ye, TANG Xianlong, DONG Shengguang

2023, 0(2):  150-154.  doi:10.13474/j.cnki.11-2246.2023.0056

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Intelligent extraction of change detection from remote sensing images is the basis of dynamic monitoring of natural resources. This paper briefly describes the history and characteristics of remote sensing image change detection technology, proposes to use three deep learning algorithms ResNet, U-Net and siamese neural network at the same time, and designs an intelligent extraction platform of remote sensing image change detection that integrates “image preprocessing, intelligent detection, and collaborative screening”, and describes the design ideas of each module in detail. Practice has shown that the integration of three deep learning algorithms is beneficial to solve problems such as difficult transformation and limited scope of application of a single deep learning algorithm, effectively improving the recall rate of remote sensing image change detection, and improving work efficiency compared with visual interpretation more than 3 times. The research results have been widely used in the “1+N” satellite monitoring of natural resources in Hunan Province.

Analysis on the spatial distribution characteristics and influencing factors of top agricultural towns in the Yangtze River Economic Belt

LI Jianhui, CHEN Lin

2023, 0(2):  155-160,166.  doi:10.13474/j.cnki.11-2246.2023.0057

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Taking 445 top agricultural towns in the Yangtze River Economic Belt as research objectives, this study investigated and revealed the spatial distribution characteristics and influencing factors with multiple methods. The methodology integrated the nearest neighbor index, disequilibrium index, kernel density analysis, spatial correlation analysis, geographic detector, et al. The results show: ①The top agricultural towns in the Yangtze River Economic Belt are differences in spatial structure, showing agglomeration distribution characteristics. ②The nuclear density shows the distribution trend of dual-core, four high, and four low. ③The top agricultural towns in the Yangtze River Economic Belt have a significant positive spatial correlation. The distribution pattern of cold and hot spots discloses the junction of the upper and middle reaches-the junction of the Yangtze River Delta is hot, and the west of upper reaches-the middle and lower reaches are cold. ④The input of agricultural industry is the leading factor affecting the spatial distribution of top agricultural towns in the Yangtze River Economic Belt. The foundation of the agricultural industry is the dominant factor, the output of the agricultural industry is the direct factor, and the location of the agricultural industry is the relevant factor.

Research on river system matching method considering structural features

JIN Shicheng, ZHANG Qingnian, CHUN Jin, YANG Nana

2023, 0(2):  161-166.  doi:10.13474/j.cnki.11-2246.2023.0058

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As a geospatial framework data in the spatial database, the river system provides the spatial structure of geospatial features. When updating and integrating geographic features in the spatial databases, it is evitable to match and update river data.Based on the analysis of the characteristics of the river system structure, this paper studies the river system matching method.And put forward: ① Two-level framework of river system matching. ② River system matching method. ③ A river matching algorithm that takes into account the hierarchical structure.The experimental results show that the matching algorithm that takes into account the hierarchical structure can reduce the number of false matches and missed matches to a certain extent, and the overall matching effect is better than the general matching algorithm.Especially in the matching of river systems with a large number of tributaries, short tributary lengths, and large gaps in river detail,the advantage is more obvious.

A construction method of global geographic name data resources based on crowd geographic name data

GUAN Xi, LONG Yuntao, SI Lianfa, WANG Meihong, ZHANG Di, HE Feng, HOU Xiaoyu

2023, 0(2):  167-171,181.  doi:10.13474/j.cnki.11-2246.2023.0059

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Oriented to the construction of global geographic information resources, in this paper, we study the production process and the critical technology of comparison analysis, data pre-processing, classification and gradation, fusion matching, density control, fault fixing, multi-language geographic name translation and quality inspection of constructing global geographic name resources based on crowd sourcing data. A rapid and large-scale production process is established, the achievements and application are introduced, aimed to providing reference for the standardization construction of global geographical names data resources.

The precision control of long distance tunneling through survey for Beijing new airport line

ZHU Shuipeng

2023, 0(2):  172-176,181.  doi:10.13474/j.cnki.11-2246.2023.0060

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In recent years, with the rapid development of economy, urban rail transit also has accelerated the pace of speed increase, and various types of large diameter shield machines have been put into the construction of subway tunnels. Compared with the traditional shield machine, the large-diameter shield machine has the characteristics of large body, heavy self weight of formed ring, large disturbance to the stratum, and so on, which has a great impact on the stability of underground control points. The shield method is used to construct the tunnel at one time. The control wire in the tunnel is generally in the form of branch wire or ring wire, with large error accumulation. Especially for long distance tunnels, the measurement accuracy control is required to be higher. Therefore, in the construction of large-diameter shield long-distance tunnel, how to ensure the accurate penetration of the shield is a new test of the measurement control technology. Taking the first phase project of the new airport line of Beijing rail transit as an example, this paper briefly describes the control process and concerns of the survey work during the actual construction of the shield section of Beihang station building (excluding)-Cigezhuang (excluding), and focuses on the precision control of the contact survey and the precision control of each detail of the survey in the tunnel. It provides reference for improving measurement accuracy in long-distance construction of large diameter shield machine.

Application of a real time difference method of improved polar quadratic datum in metro automatic monitoring

HUANG Xiaobin, JIANG Yexiang, HU Leiming

2023, 0(2):  177-181.  doi:10.13474/j.cnki.11-2246.2023.0061

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In view of the problem that the measurement results of the automated monitoring system in the subway protection area are easily affected by temperature, humidity, air pressure, atmospheric refraction, train vibration and other factors, and it is extremely difficult to conduct quantitative analysis on a certain factor, therefore, this paper proposes an improved polar coordinate secondary datum real time difference method, builds the automated monitoring system based on the new method and carries out accuracy evaluation, Case analysis shows that the new method can effectively weaken the impact of external environmental factors on the measurement results, accurately obtain the three-dimensional coordinates of monitoring points, further improve the monitoring accuracy of the automated monitoring system, and more accurately feedback the impact of external construction on the rail transit structure.