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  • MDPI AG  (15)
  • Cartography and geographic base data  (15)
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  • MDPI AG  (15)
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  • Cartography and geographic base data  (15)
  • 1
    Online Resource
    Online Resource
    Urban Green Plastic Cover Mapping Based on VHR Remote Sensing Images and a Deep Semi-Supervised Learning Framework
    MDPI AG ; 2020
    In:  ISPRS International Journal of Geo-Information Vol. 9, No. 9 ( 2020-09-02), p. 527-
    Details
    In: ISPRS International Journal of Geo-Information, MDPI AG, Vol. 9, No. 9 ( 2020-09-02), p. 527-
    Abstract: With the rapid process of both urban sprawl and urban renewal, large numbers of old buildings have been demolished in China, leading to wide spread construction sites, which could cause severe dust contamination. To alleviate the accompanied dust pollution, green plastic mulch has been widely used by local governments of China. Therefore, timely and accurate mapping of urban green plastic covered regions is of great significance to both urban environmental management and the understanding of urban growth status. However, the complex spatial patterns of the urban landscape make it challenging to accurately identify these areas of green plastic cover. To tackle this issue, we propose a deep semi-supervised learning framework for green plastic cover mapping using very high resolution (VHR) remote sensing imagery. Specifically, a multi-scale deformable convolution neural network (CNN) was exploited to learn representative and discriminative features under complex urban landscapes. Afterwards, a semi-supervised learning strategy was proposed to integrate the limited labeled data and massive unlabeled data for model co-training. Experimental results indicate that the proposed method could accurately identify green plastic-covered regions in Jinan with an overall accuracy (OA) of 91.63%. An ablation study indicated that, compared with supervised learning, the semi-supervised learning strategy in this study could increase the OA by 6.38%. Moreover, the multi-scale deformable CNN outperforms several classic CNN models in the computer vision field. The proposed method is the first attempt to map urban green plastic-covered regions based on deep learning, which could serve as a baseline and useful reference for future research.
    Type of Medium: Online Resource
    ISSN: 2220-9964
    URL: Article
    DOI: 10.3390/ijgi9090527
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
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  • 2
    Online Resource
    Online Resource
    Spatial and Temporal Characteristics of Urban Tourism Travel by Taxi—A Case Study of Shenzhen
    MDPI AG ; 2021
    In:  ISPRS International Journal of Geo-Information Vol. 10, No. 7 ( 2021-06-30), p. 445-
    Details
    In: ISPRS International Journal of Geo-Information, MDPI AG, Vol. 10, No. 7 ( 2021-06-30), p. 445-
    Abstract: Tourism networks are an important research part of tourism geography. Despite the significance of transportation in shaping tourism networks, current studies have mainly focused on the “daily behavior” of urban travel at the expense of tourism travel, which has been regarded as an “exceptional behavior”. To fill this gap, this study proposes a framework for exploring the spatial and temporal characteristics of urban tourism travel by taxi. We chose Shenzhen, a densely populated mega-city in China with abundant tourism resources, as a case study. First, we extracted tourist trips from taxi trajectories and used kernel density estimation to analyze the spatial aggregation characteristics of tourist trip origins. Second, we investigated the spatial dependence of tourist trips using local spatial autocorrelation analysis (Getis-Ord Gi*). Third, we explored the correlations between the tourist trip origins and urban geographic contextual factors (e.g., catering services and transportation facilities) using a geographically weighted regression model. The results show the following: (1) the trends between the coverage of tourist travel networks and the volume of tourist trips are similar; (2) the spatial interaction intensity of urban tourism has grouping and hierarchical characteristics; and (3) the spatial distribution of tourist trips by taxi is uneven and influenced by the distribution of urban morphology, tourism resources, and the preferences of taxi pick-up passengers. Our proposed framework and revealed spatial and temporal patterns have implications for urban tourism traffic planning, tourism product development, and tourist flow control in tourist attractions.
    Type of Medium: Online Resource
    ISSN: 2220-9964
    URL: Article
    DOI: 10.3390/ijgi10070445
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
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  • 3
    Online Resource
    Online Resource
    Small Manhole Cover Detection in Remote Sensing Imagery with Deep Convolutional Neural Networks
    MDPI AG ; 2019
    In:  ISPRS International Journal of Geo-Information Vol. 8, No. 1 ( 2019-01-19), p. 49-
    Details
    In: ISPRS International Journal of Geo-Information, MDPI AG, Vol. 8, No. 1 ( 2019-01-19), p. 49-
    Abstract: With the development of remote sensing technology and the advent of high-resolution images, obtaining data has become increasingly convenient. However, the acquisition of small manhole cover information still has shortcomings including low efficiency of manual surveying and high leakage rate. Recently, deep learning models, especially deep convolutional neural networks (DCNNs), have proven to be effective at object detection. However, several challenges limit the applications of DCNN in manhole cover object detection using remote sensing imagery: (1) Manhole cover objects often appear at different scales in remotely sensed images and DCNNs’ fixed receptive field cannot match the scale variability of such objects; (2) Manhole cover objects in large-scale remotely-sensed images are relatively small in size and densely packed, while DCNNs have poor localization performance when applied to such objects. To address these problems, we propose an effective method for detecting manhole cover objects in remotely-sensed images. First, we redesign the feature extractor by adopting the visual geometry group (VGG), which can increase the variety of receptive field size. Then, detection is performed using two sub-networks: a multi-scale output network (MON) for manhole cover object-like edge generation from several intermediate layers whose receptive fields match different object scales and a multi-level convolution matching network (M-CMN) for object detection based on fused feature maps, which combines several feature maps that enable small and densely packed manhole cover objects to produce a stronger response. The results show that our method is more accurate than existing methods at detecting manhole covers in remotely-sensed images.
    Type of Medium: Online Resource
    ISSN: 2220-9964
    URL: Article
    DOI: 10.3390/ijgi8010049
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
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  • 4
    Online Resource
    Online Resource
    Distance-Decay Effect in Probabilistic Time Geography for Random Encounter
    MDPI AG ; 2019
    In:  ISPRS International Journal of Geo-Information Vol. 8, No. 4 ( 2019-04-04), p. 177-
    Details
    In: ISPRS International Journal of Geo-Information, MDPI AG, Vol. 8, No. 4 ( 2019-04-04), p. 177-
    Abstract: Probabilistic time geography uses a fixed distance threshold for the definition of the encounter events of moving objects. However, because of the distance-decay effect, different distances within the fixed threshold ensure that the encounter events do not always have the same possibility, and, therefore, the quantitative probabilistic time geography analysis needs to consider the actual distance-decay coefficient (DDC). Thus, this paper introduces the DDC and proposes a new encounter probability measure model that takes into account the distance-decay effect. Given two positions of a pair of moving objects, the traditional encounter probability model is that if the distance between the two positions does not exceed a given threshold, the encounter event may occur, and its probability is equal to the product of the probabilities of the two moving objects in their respective positions. Furthermore, the probability of the encounter at two given positions is multiplied by the DDC in the proposed model, in order to express the influence of the distance-decay effect on the encounter probability. Finally, the validity of the proposed model is verified by an experiment, which uses the tracking data of wild zebras to calculate the encounter probability, and compares it with the former method.
    Type of Medium: Online Resource
    ISSN: 2220-9964
    URL: Article
    DOI: 10.3390/ijgi8040177
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
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  • 5
    Online Resource
    Online Resource
    Saline-Soil Deformation Extraction Based on an Improved Time-Series InSAR Approach
    MDPI AG ; 2021
    In:  ISPRS International Journal of Geo-Information Vol. 10, No. 3 ( 2021-02-27), p. 112-
    Details
    In: ISPRS International Journal of Geo-Information, MDPI AG, Vol. 10, No. 3 ( 2021-02-27), p. 112-
    Abstract: Significant seasonal fluctuations could occur in the regional scattering characteristics and surface deformation of saline soil, and cause decorrelation, which limits the application of the conventional time-series InSAR (TS-InSAR). For extending the saline-soil deformation monitoring capability, this paper presents an improved TS-InSAR approach, based on the interferometric coherence statistics and high-coherence interferogram refinement. By constructing a network of the refined interferograms, high-accuracy ground deformation can be extracted through the weighted least square estimation and the coherent target refinement. To extract the high-accuracy deformation of a representative saline soil area in the Qarhan Salt Lake, 119 C-band Sentinel-1A images collected between May 2015 and May 2020 are selected as the data source. Subsequently, 845 refined interferograms are selected from all possible interferograms to conduct the network inversion, based on the related thresholds (the temporal baseline 〈 49 days, the average spatial coherences 〉 0.5, respectively). Compared with the conventional TS-InSAR measurements, both the accuracy and reliability of the extracted deformation results of the saline soil increased dramatically. Furthermore, the testing results indicate that the improved TS-InSAR method has advantages on the deformation extraction in the saline soil region, and is adaptive to reflecting the typical seasonal variations of the saline soil.
    Type of Medium: Online Resource
    ISSN: 2220-9964
    URL: Article
    DOI: 10.3390/ijgi10030112
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
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  • 6
    Online Resource
    Online Resource
    A Virtual Geographic Environment for Debris Flow Risk Analysis in Residential Areas
    MDPI AG ; 2017
    In:  ISPRS International Journal of Geo-Information Vol. 6, No. 11 ( 2017-11-22), p. 377-
    Details
    In: ISPRS International Journal of Geo-Information, MDPI AG, Vol. 6, No. 11 ( 2017-11-22), p. 377-
    Abstract: Emergency risk assessment of debris flows in residential areas is of great significance for disaster prevention and reduction, but the assessment has disadvantages, such as a low numerical simulation efficiency and poor capabilities of risk assessment and geographic knowledge sharing. Thus, this paper focuses on the construction of a VGE (virtual geographic environment) system that provides an efficient tool to support the rapid risk analysis of debris flow disasters. The numerical simulation, risk analysis, and 3D (three-dimensional) dynamic visualization of debris flow disasters were tightly integrated into the VGE system. Key technologies, including quantitative risk assessment, multiscale parallel optimization, and visual representation of disaster information, were discussed in detail. The Qipan gully in Wenchuan County, Sichuan Province, China, was selected as the case area, and a prototype system was developed. According to the multiscale parallel optimization experiments, a suitable scale was chosen for the numerical simulation of debris flow disasters. The computational efficiency of one simulation step was 5 ms (milliseconds), and the rendering efficiency was approximately 40 fps (frames per second). Information about the risk area, risk population, and risk roads under different conditions can be quickly obtained. The experimental results show that our approach can support real-time interactive analyses and can be used to share and publish geographic knowledge.
    Type of Medium: Online Resource
    ISSN: 2220-9964
    URL: Article
    DOI: 10.3390/ijgi6110377
    Language: English
    Publisher: MDPI AG
    Publication Date: 2017
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  • 7
    Online Resource
    Online Resource
    Landscape Pattern Theoretical Optimization of Urban Green Space Based on Ecosystem Service Supply and Demand
    MDPI AG ; 2021
    In:  ISPRS International Journal of Geo-Information Vol. 10, No. 4 ( 2021-04-14), p. 263-
    Details
    In: ISPRS International Journal of Geo-Information, MDPI AG, Vol. 10, No. 4 ( 2021-04-14), p. 263-
    Abstract: Assessing the supply and demand of urban green space (UGS) ecosystem services (ESs) can provide relevant insights for urban planning. This study presents an analysis method for the spatial distribution of UGS ES supply and demand at administrative unit and 1-m grid scales and directly compares the matches of ES supply and demand in spatially explicit maps at two scales. Based on the analysis results at administrative unit scale, administrative units with an unbalanced UGS ES supply and demand were divided into three types: (Ⅰ) lack of green space; (Ⅱ) unreasonable green space structure; (Ⅲ) comprehensive, and different optimization schemes were put forward. According to the analysis results at 1-m scale, the regions with an unbalanced ES supply and demand of an administrative unit were divided into the following: (1) severe ES shortage area; (2) moderate ES shortage area; (3) mild ES shortage area, and the severe ES shortage area was taken as the UGS optimization area. We take the UGS within the 5th Ring Road of Beijing as an example and propose suggestions for optimizing the UGS pattern based on the evaluation of the supply and demand of UGS carbon sequestration services and purification services for particulate matter with an aerodynamic diameter 〈 2.5 µm (PM2.5). This study provides an easy-to-use evaluation method for the spatial distribution of UGS ES supply and demand and proposes different optimization suggestions for the unbalanced area, thus playing a role in UGS construction activities and green space structure optimization.
    Type of Medium: Online Resource
    ISSN: 2220-9964
    URL: Article
    DOI: 10.3390/ijgi10040263
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
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  • 8
    Online Resource
    Online Resource
    Improved Jitter Elimination and Topology Correction Method for the Split Line of Narrow and Long Patches
    MDPI AG ; 2018
    In:  ISPRS International Journal of Geo-Information Vol. 7, No. 10 ( 2018-10-11), p. 402-
    Details
    In: ISPRS International Journal of Geo-Information, MDPI AG, Vol. 7, No. 10 ( 2018-10-11), p. 402-
    Abstract: Extracting the split line of narrow and long patches is important for the generalization of land-use thematic data. There are two commonly used methods for extracting the split lines: One is based on Delaunay triangulation and the other is based on straight skeletons. However, it is difficult for the straight skeleton method to preserve geometric structure and topological consistency with the original data when dealing with polygons that have irregularity and complexity of junctions. Therefore, we propose an improved jitter elimination and topology correction method for split lines based on a constrained Delaunay triangulation. First, a split line adjustment algorithm based on the geometric structure of the polygon is proposed to eliminate the jitters. Second, a split line topology correction algorithm is proposed for nodes with degree 1 or degree 2, considering the boundary topological constraint. The reliability of the proposed method is verified by comparing it with the straight skeleton method using sample data and the superiority of the proposed method is verified by using actual data from China’s geographical conditions census in the Guizhou province.
    Type of Medium: Online Resource
    ISSN: 2220-9964
    URL: Article
    DOI: 10.3390/ijgi7100402
    Language: English
    Publisher: MDPI AG
    Publication Date: 2018
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  • 9
    Online Resource
    Online Resource
    Assessing Spatial Accessibility of Public and Private Residential Aged Care Facilities: A Case Study in Wuhan, Central China
    MDPI AG ; 2017
    In:  ISPRS International Journal of Geo-Information Vol. 6, No. 10 ( 2017-10-16), p. 304-
    Details
    In: ISPRS International Journal of Geo-Information, MDPI AG, Vol. 6, No. 10 ( 2017-10-16), p. 304-
    Abstract: In the increasingly serious aging China, aged service is the provision of one of the most urgent and important public services to citizens, and private facilities has become an important service force with the aged service market opening in China. This study aims to explore the spatial variation in the accessibility of residential aged care facilities (RACFs) and compared the service capacity of public RACFs and private RACFs. It facilitates RACFs to be allocated rationally in the future and achieve the equalization of aged services. A village-level analysis of spatial access to public and private RACFs by the multi-catchment sizes Gaussian two-step floating catchment area (MCSG2SFCA) method was conducted through a case study in Wuhan City in Central China. The major results are as follows: (1) the accessibility of RACFs in urban areas is better than that in rural areas; (2) the public RACFs still dominate aged care services but the role of private RACFs is important as well; (3) in developed urban areas, the accessibility to private RACFs surpasses that of public ones, and the situation is opposite in rural areas; (4) the capacity of aged care services in Wuhan is not high, meanwhile there is remarkable regional disparity. The accessibility of RACFs in Wuhan is not satisfactory, and there is a significant gap between urban and rural areas. The private RACFs have significantly improved the urban capacity of aged care services, but the role in rural areas is still very weak.
    Type of Medium: Online Resource
    ISSN: 2220-9964
    URL: Article
    DOI: 10.3390/ijgi6100304
    Language: English
    Publisher: MDPI AG
    Publication Date: 2017
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  • 10
    Online Resource
    Online Resource
    Probabilistic Model of Random Encounter in Obstacle Space
    MDPI AG ; 2019
    In:  ISPRS International Journal of Geo-Information Vol. 8, No. 1 ( 2019-01-15), p. 32-
    Details
    In: ISPRS International Journal of Geo-Information, MDPI AG, Vol. 8, No. 1 ( 2019-01-15), p. 32-
    Abstract: Based on probabilistic time-geography, the encounter between two moving objects is random. The quantitative analysis of the probability of encounter needs to consider the actual geographical environment. The existing encounter probability algorithm is based on homogeneous space, ignoring the wide range of obstacles and their impact on encounter events. Based on this, this paper introduces obstacle factors, proposes encounter events that are constrained by obstacles, and constructs a model of the probability of encounters of moving objects based on the influence of obstacles on visual perception with the line-of-sight view analysis principle. In realistic obstacle space, this method provides a quantitative basis for predicting the encountering possibility of two mobile objects and the largest possible encounter location. Finally, the validity of the model is verified by experimental results. The model uses part of the Wuhan digital elevation model (DEM) data to calculate the encounter probability of two moving objects on it, and analyzes the temporal and spatial distribution characteristics of these probabilities.
    Type of Medium: Online Resource
    ISSN: 2220-9964
    URL: Article
    DOI: 10.3390/ijgi8010032
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
    detail.hit.zdb_id: 2655790-3
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