scholarly journals MONITORING THE SPATIO-TEMPORAL TRAJECTORY OF URBAN AREA HOTSPOTS IN WUHAN, CHINA USING TIME-SERIES NIGHTTIME LIGHT IMAGES

2019 ◽  
Vol XLII-4/W20 ◽  
pp. 71-76
Author(s):  
Y. L. Ruan ◽  
Y. H. Zou
Keyword(s):  
Urban Area ◽  
Human Activities ◽  
Urban Expansion ◽  
Data Sets ◽  
Threshold Method ◽  
Expansion Pattern ◽  
Nighttime Light ◽  
Spatio Temporal ◽  
Urban Extent ◽  
The Impact

Abstract. Urban area hotspots can be considered as an ideal representation of spatial heterogeneity of human activities within a city, which is susceptible to regional urban expansion pattern pattern. However, in previous studies most researchers focused on extracting urban extent, leaving the interior variation of nighttime radiance intensity poorly explored. With the help of multi-source data sets such as DMSP/OLS (NTL), LST and NDVI, we proposed an applicable framework to identify and monitor the spatiotemporal trajectory of polycentric urban area hotspots. Firstly, the original NTL dataset were calibrated to reduce inconsistency and discontinuity. And we integrated NTL, LST as well as NDVI and established an urban index TVANUI capturing the approximate urban extents. Secondly, multi-resolution segmentation algorithm, neighborhood statistics analysis and a local-optimized threshold method were employed to get more precise urban extent with an overall accuracy above 85% and a Kappa above 0.70. Thirdly, the urban extents were utilized as masks to get corresponding radiance intensity from calibrated NTL. Finally, we established the Gaussian volume model for each cluster and the resulting parameters were used to quantitatively depict hotspot features (i.e., intensity, morphology and centroid dynamics). All the identified urban hotspot showed our framework could successfully capture polycentric urban hotspots, whose fitting coefficients were over 0.7. The spatiotemporal trajectory of hotspot powerfully revealed the impact of the regional urban growth pattern and planning strategies on human activities in the city of Wuhan. This study provides important insights for further studies on the relationship between the regional urbanization and human activities.

scholarly journals Spatio-temporal variation of water supply in Guizhou Province, China

Water Policy ◽  
2016 ◽  
Vol 19 (1) ◽  
pp. 181-195 ◽  
Author(s):  
Huiqing Han ◽  
Yuxiang Dong
Keyword(s):  
Land Use ◽  
Water Supply ◽  
Urban Expansion ◽  
Guizhou Province ◽  
Water Yield ◽  
Freshwater Ecosystem ◽  
Yield Model ◽  
Invest Model ◽  
Spatio Temporal ◽  
The Impact

Water supply is an important freshwater ecosystem service provided by ecosystems. Water shortages resulting from spatio-temporal heterogeneity of climate condition or human activities present serious problems in the Guizhou Province of southwest China. This study aimed to analyze the spatio-temporal changes of water supply service using the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model, explore how climate and land-use changes impact water supply provision, and discuss the impact of parameters associated with climate and land-use in the InVEST model on water supply in the region. We used data and the model to forecast trends for the year 2030 and found that water supply has been declining in the region at the watershed scale since 1990. Climate and land-use change played important roles in affecting the water supply. Water supply was overwhelmingly driven by the reference evapotranspiration and annual average precipitation, while the plant evapotranspiration coefficients for each land-use type had a relatively small effect. The method for sensitivity analysis developed in this study allowed exploration of the relative importance of parameters in the InVEST water yield model. The Grain-for-Green project, afforestation, and urban expansion control should be accelerated in this region to protect the water supply.

scholarly journals Continuous Monitoring of the Spatio-Temporal Patterns of Surface Water in Response to Land Use and Land Cover Types in a Mediterranean Lagoon Complex

2019 ◽  
Vol 11 (12) ◽  
pp. 1425 ◽  
Author(s):  
Zhichao Li ◽  
Yujie Feng ◽  
Nadine Dessay ◽  
Eric Delaitre ◽  
Helen Gurgel ◽  
...  
Keyword(s):  
Surface Water ◽  
Human Activities ◽  
Coastal Wetlands ◽  
Annual Variation ◽  
Coastal Lagoons ◽  
Sand Beach ◽  
Mediterranean Lagoon ◽  
Potential Link ◽  
Spatio Temporal ◽  
The Impact

Mediterranean coastal lagoons and their peripheral areas often provide a collection of habitats for many species, and they often face significant threats from anthropogenic activities. Diverse human activities in such areas directly affect the spatio-temporal dynamic of surface water and its ecological characteristics. Monitoring the surface water dynamic, and understanding the impact of human activities are of great significance for coastal lagoon conservation. The Regional Natural Park of Narbonne includes a typical Mediterranean lagoon complex where surface water dynamic and its potential link with local diverse human activities has not yet been studied. In this context, based on all the available Landsat images covering the study area during 2002–2016, this study identified the water and non-water classes for each satellite observation by comparing three widely used spectral indices (i.e., NDVI, NDWI and MNDWI) and using the Otsu method. The yearly water frequency index was then computed to present the spatio-temporal dynamic of surface water for each year, and three water dynamic scenarios were also identified for each year: permanent water (PW), non-permanent water (NPW) and non-water (NW). The spatial and inter-annual variation in the patterns of the three water scenarios were characterized by computing the landscape metrics at scenario-level quantifying area/edge, shape, aggregation and fragmentation. Finally, the quantitative link between different land use and land cover (LULC) types derived from the LULC maps of 2003, 2012 and 2015 and the surface water dynamic scenarios was established in each of the 300 m × 300 m grid cells covering the study area to determine the potential impact of human activities on the surface water dynamic. In terms of the inter-annual variation during 2002–2016, PW presented an overall stability, and NPW occupied only a small part of the water surface in each year and presented an inter-annual fluctuation. NPW had a smaller patch size, with lower connectivity degree and higher fragmentation degree. In terms of spatial variation during 2002–2016, NPW often occurred around PW, and its configurational features varied from place to place. Moreover, PW mostly corresponded to the natural lagoon, and salt marsh (as a part of lagoons), and NPW had a strong link with arable land (agricultural irrigation) and salt marsh (salt production), sand beach/dune, coastal wetlands and lagoon for the LULC maps of 2003, 2012 and 2015. However, more in-depth analysis is required for understanding the impact of sand beach/dune, coastal wetlands and lagoon on surface water dynamics. This study covers the long-term variations of surface water patterns in a Mediterranean lagoon complex having intense and diverse human activities, and the potential link between LULC types and the water dynamic scenarios was investigated on different dates. The results of the study should be useful for environmental management and protection of coastal lagoons.

Savitzky–Golay smoothing and differentiation for polymerase chain reaction quantification

2018 ◽  
Vol 96 (3) ◽  
pp. 380-389 ◽  
Author(s):  
Charles Gaudreault ◽  
Joanny Salvas ◽  
Joël Sirois
Keyword(s):  
Relative Error ◽  
Logistic Model ◽  
Data Sets ◽  
Threshold Method ◽  
Chain Reaction ◽  
Quantification Method ◽  
Curve Modeling ◽  
Polymerase Chain ◽  
The Impact ◽  
Inter Assay Variation

In quantitative PCR (qPCR), replicates can minimize the impact of intra-assay variation; however, inter-assay variations must be minimized to obtain a robust quantification method. The method proposed in this study uses Savitzky–Golay smoothing and differentiation (SGSD) to identify a derivative-maximum-based cycle of quantification. It does not rely on curve modeling, as is the case with many existing techniques. PCR fluorescence data sets challenged for inter-assay variations (different thermocycler units, different reagents batches, different operators, different standard curves, and different labs) were used for the evaluation. The algorithm was compared with a four-parameter logistic model (4PLM) method, the Cy0 method, and the threshold method. The SGSD method compared favourably with all methods in terms of inter-assay variation. SGSD was statistically different from the 4PLM (P = 0.03), Cy0 (P = 0.05), and threshold (P = 0.004) methods on relative error comparison basis. For intra-assay variations, SGSD outperformed the threshold method (P = 0.005) and equalled the 4PLM and Cy0 methods (P > 0.05) on relative error basis. Our results demonstrate that the SGSD method could potentially be an alternative to sigmoid modeling based methods (4PLM and Cy0) when PCR data are challenged for inter-assay variations.

scholarly journals Spatio-Temporal Evaluation of Urban Growth of Zuru Metropolis, Nigeria

2021 ◽  
Vol 5 (2) ◽  
pp. 456-467
Author(s):  
Y.A. Maleeks ◽  
A.O. Aliyu ◽  
A. Bala ◽  
A.U. Isiaka ◽  
K.Z. Atta
Keyword(s):  
Population Growth ◽  
Urban Area ◽  
Urban Growth ◽  
Water Body ◽  
Anthropogenic Activities ◽  
Landsat Imagery ◽  
Urban Expansion ◽  
Population Increase ◽  
Urban Dynamics ◽  
Spatio Temporal

The pattern of development in a city is mostly governed by urban dynamics, with population increase being the primary driving force. Built-up cover is the most important predictor of urban expansion. Zuru metropolis in Kebbi State has witnessed remarkable developmental activities caused by human influences such as buildings, road constructions, and population growth for over decades. Urban growth was ascertained for a period of 30 years through the analysis of Landsat imagery of 1988, 1998, 2008 and 2018. The datasets were classified into five (5) land covers, namely, built-up, water body, rocky surface, vegetation, and others. Quantitative assessment of the urban growth was ascertained by computing post-classification LC dynamics and Land Consumption Rate/Land Absorption Coefficient (LCR/LAC). The results showed that the built-up cover (urban area) conspicuously increased with area of 693.35 ha, 728.74 ha, 5210.5 ha and 6845.75 ha respectively for the period of study (1988 – 2018). The increment in built-up area was indicative of population growth from 1988 to 2018. The study revealed that between 1988 to 2018 showed that built-up increased by 11.78%, while rocky surface and water body have shrunk by 16.44% and 0.02% respectively, which can be attributed to anthropogenic activities in which rocky surface and waterbody have been transformed into built-up cover. It further revealed that the urban area experienced crowdedness in the years 2008 and 2018 respectively due to high LCR values of 2.71% compared to LCR values of 0.0714% and 0.0558% in 1988 and 1998. Land transformation into urban area and spread of the population to the outskirts of the study area was prominent between 1998 and 2008 due to high LAC value of 0.0998. The study concluded that there was transformation of rocky surface and waterbody into urban area, which was caused by population growth, human and agricultural activities in Zuru metropolis.

scholarly journals An Unsupervised Urban Extent Extraction Method from NPP-VIIRS Nighttime Light Data

2020 ◽  
Vol 12 (22) ◽  
pp. 3810
Author(s):  
Xiuxiu Chen ◽  
Feng Zhang ◽  
Zhenhong Du ◽  
Renyi Liu
Keyword(s):  
Clustering Algorithm ◽  
Urban Expansion ◽  
Spatial Context ◽  
Support Vector ◽  
Free Access ◽  
Urban Edge ◽  
Nighttime Light Data ◽  
Nighttime Light ◽  
Urban Mapping ◽  
Urban Extent

An accelerating trend of global urbanization accompanying various environmental and urban issues makes frequently urban mapping. Nighttime light data (NTL) has shown great advantages in urban mapping at regional and global scales over long time series because of its appropriate spatial and temporal resolution, free access, and global coverage. However, the existing urban extent extraction methods based on nighttime light data rely on auxiliary data and training samples, which require labor and time for data preparation, leading to the difficulty to extract urban extent at a large scale. This study seeks to develop an unsupervised method to extract urban extent from nighttime light data rapidly and accurately without ancillary data. The clustering algorithm is applied to segment urban areas from the background and multi-scale spatial context constraints are utilized to reduce errors arising from the low brightness areas and increase detail information in urban edge district. Firstly, the urban edge district is detected using spatial context constrained clustering, and the NTL image is divided into urban interior district, urban edge district and non-urban interior district. Secondly, the urban edge pixels are classified by an adaptive direction filtering clustering. Finally, the full urban extent is obtained by merging the urban inner pixels and the urban pixels in urban edge district. The proposed method was validated using the urban extents of 25 Chinese cities, obtained by Landsat8 images and compared with two common methods, the local-optimized threshold method (LOT) and the integrated night light, normalized vegetation index, and surface temperature support vector machine classification method (INNL-SVM). The Kappa coefficient ranged from 0.687 to 0.829 with an average of 0.7686 (1.80% higher than LOT and 4.88% higher than INNL-SVM). The results in this study show that the proposed method is a reliable and efficient method for extracting urban extent with high accuracy and simple operation. These imply the significant potential for urban mapping and urban expansion research at regional and global scales automatically and accurately.

scholarly journals Use of historical information in extreme-surge frequency estimation: the case of marine flooding on the La Rochelle site in France

2015 ◽  
Vol 15 (7) ◽  
pp. 1515-1531 ◽  
Author(s):  
Y. Hamdi ◽  
L. Bardet ◽  
C.-M. Duluc ◽  
V. Rebour
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Frequency Estimation ◽  
Atlantic Coast ◽  
Historical Period ◽  
Data Sets ◽  
Nuclear Facilities ◽  
Threshold Method ◽  
Historical Information ◽  
The Impact

Abstract. Nuclear power plants located in the French Atlantic coast are designed to be protected against extreme environmental conditions. The French authorities remain cautious by adopting a strict policy of nuclear-plants flood prevention. Although coastal nuclear facilities in France are designed to very low probabilities of failure (e.g., 1000-year surge), exceptional surges (outliers induced by exceptional climatic events) have shown that the extreme sea levels estimated with the current statistical approaches could be underestimated. The estimation of extreme surges then requires the use of a statistical analysis approach having a more solid theoretical motivation. This paper deals with extreme-surge frequency estimation using historical information (HI) about events occurred before the systematic record period. It also contributes to addressing the problem of the presence of outliers in data sets. The frequency models presented in the present paper have been quite successful in the field of hydrometeorology and river flooding but they have not been applied to sea level data sets to prevent marine flooding. In this work, we suggest two methods of incorporating the HI: the peaks-over-threshold method with HI (POTH) and the block maxima method with HI (BMH). Two kinds of historical data can be used in the POTH method: classical historical maxima (HMax) data, and over-a-threshold supplementary (OTS) data. In both cases, the data are structured in historical periods and can be used only as complement to the main systematic data. On the other hand, in the BMH method, the basic hypothesis in statistical modeling of HI is that at least one threshold of perception exists for the whole period (historical and systematic) and that during a giving historical period preceding the period of tide gauging, only information about surges above this threshold have been recorded or archived. The two frequency models were applied to a case study from France, at the La Rochelle site where the storm Xynthia induced an outlier, to illustrate their potentials, to compare their performances and especially to analyze the impact of the use of HI on the extreme-surge frequency estimation.

scholarly journals DYNAMICS OF SPATIO-TEMPORAL URBAN EXPANSION IN SOUTH WEST DELHI REGION: A GEO-SPATIAL APPROACH FOR URBAN DISASTER MANAGEMENT

2019 ◽  
Vol XLII-3/W8 ◽  
pp. 373-379
Author(s):  
N. Sharma ◽  
A. Kaur ◽  
P. Bose
Keyword(s):  
Land Use ◽  
Land Cover ◽  
Natural Resources ◽  
Land Cover Change ◽  
Rural Areas ◽  
Urban Areas ◽  
Urban Expansion ◽  
Urban Disaster ◽  
Spatio Temporal ◽  
The Impact

<p><strong>Abstract.</strong> Constantly increasing population and up-scaling economic growth has certainly contributed to fast-paced urban expansion, but simultaneously, as a result, has developed immense pressure on our natural resources. Among other unfavorable consequences, this has led to significant changes in the land use and land cover patterns in megacities all across the globe. As the impact of uncontrolled and unplanned development continues to alter life patterns, it has become imperative to study severe problems resulting from rapid development and leading to environmental pollution, disruptions in ecological structures, ever increasing pressure on natural resources and recurring urban disasters This paper presents an approach to address these challenges using geospatial data to study the land use and land cover change and the patterns and processes of urban growth. Spatio-temporal changes in land-use/land-cover were assessed over the years using multi-date high resolution satellite data. The land use classification was conducted using visual image interpretation technique wherein, study area was categorized into five different classes based on NRSC classification system namely agricultural, built-up, urban green (forest), and fallow land and water bodies. Post-classification change detection technique was used for the assessment of land-cover change and transition matrices of urban expansion were developed to quantify the changes. The results show that the city has been expanding majorly in its borders, where land masses have been converted from agriculture based rural areas to urban structures. An increase in the built-up category was observed with the transformation of agricultural and marginal land with an approximate change of 8.62% in the peri-urban areas. Urban areas are becoming more densely populated and open barren lands are converted into urban areas due to over population and migration from the rural areas of Delhi and thus increasing threat towards urban disaster. Conservation and sustainable management of various natural resources is recommended in order to minimize the impact of potential urban disasters.</p>

Impact of Urbanization on the Spatial Sustainability of A City - A Case Study of Yantai

2012 ◽  
Vol 524-527 ◽  
pp. 2724-2730
Author(s):  
Xiao Hui Ding ◽  
Wei Zhou Zhong ◽  
Shuo Xin Zhang ◽  
Yu Jiang
Keyword(s):  
Urban Area ◽  
Planning Process ◽  
Urban Expansion ◽  
Spatial Dimension ◽  
Medium Resolution ◽  
Development Indicator ◽  
Urbanization Rate ◽  
Impact Of Urbanization ◽  
The Impact

Urbanization is a major factor that shapes the pattern of urban area of cities and exerts influence on cities’ development. The pattern of urban expansion and sprawl is considered as the main feature for evaluating the development of a city, which can dramatically reflect the path of urbanization and largely influence the potential of sustainability of a city. The objectives of this study were to introduce a sustainable development indicator - compact coefficient of urban area (CCUA), specially designed for evaluating the sustainability of a city in spatial dimension, and reveal the impact of urbanization on the sustainability of a city through comparing the trend of urbanization rate of a city with its changes of CCUA. A case study has been taken in Yantai, a medium-sized city in east part of China. Remote sensing was used for mapping the land use/land cover changes of urban area in Yantai from 1990 to 2010 by using the medium-resolution satellite imagery. Then, five indexes of ecological landscape were selected and processed, and CCUA of Yantai was calculated. Results of this study indicate that CCUA is an efficient indicator for measuring the sustainability of the pattern of urban expansion, which can assist the urban planning process of professionals and facilitate the decision-making process of local government.

scholarly journals Human Activities Enhance Radiation Forcing through Surface Albedo Associated with Vegetation in Beijing

2020 ◽  
Vol 12 (5) ◽  
pp. 837 ◽  
Author(s):  
Xiying Tang ◽  
Yaoping Cui ◽  
Nan Li ◽  
Yiming Fu ◽  
Xiaoyan Liu ◽  
...  
Keyword(s):  
Land Cover ◽  
Human Activities ◽  
Urban Areas ◽  
Radiative Forcing ◽  
Surface Albedo ◽  
Urban Expansion ◽  
Radiation Energy ◽  
Vegetation Growth ◽  
Land Cover Types ◽  
The Impact

The impact of human activities on vegetation has been the focus of much research, but the impact on radiation energy through surface albedo associated with vegetation greenness and length of the growth season is still not well documented. Based on the land cover data for the years 2000 and 2015, this study first divided the land cover change in Beijing from 2000 to 2015 into five types according to the impact of human activities and vegetation resilience, namely, old urban areas (OU), urban expansion areas (UE), cropland (CP), mixed pixel areas (MP, which means the land covers other than urban expansion which had changed from 2000 to 2015), and the residual vegetation cover areas (pure pixels (PP), dominated by natural and seminatural vegetation, such as grassland, forest, and wetland). Then, we calculated the direct radiative forcing from the albedo change from 2000 to 2015 and analyzed the effect of vegetation on the albedo under different land cover types based on multi-resource Moderate Resolution Imaging Spectroradiometer (MODIS) products of vegetation, albedo, and solar radiation. The results showed that the most typical changes in land cover were from urban expansion. By comparing the PP with the four human-affected land cover types (OU, UE, MP, and CP), we confirmed that the radiative forcing increment between 2001–2003 and 2013–2015 in PP (0.01 W/m2) was much smaller than that in the four human-affected land cover types (the mean increment was 0.92 W/m2). This study highlights that human activities affected vegetation growth. This, in turn, brought changes in the albedo, thereby enhancing radiative forcing in Beijing during 2000–2015.

scholarly journals Urban Expansion and Its Impact on the Livelihood of Peripheral Farming Communities: The Case of Assosa Town, Benishangul Gumuz Region, Ethiopia

2020 ◽  
Vol 8 (2) ◽  
pp. 21
Author(s):  
Tadele Tesfaye Labiso
Keyword(s):  
Urban Areas ◽  
Urban Expansion ◽  
Group Discussion ◽  
Sampling Technique ◽  
Farming Communities ◽  
Policy And Strategy ◽  
Expansion Pattern ◽  
Horizontal Expansion ◽  
Rural Dwellers ◽  
The Impact

Assosa town’s expansion program which had been experiencing a horizontal expansion starting from its historical expansion pattern currently implemented via expropriating peripheral land holders of earlier rural dwellers by solely decision of town administration and the investigation randomly targeted to per-urban areas from four peripheral kebeles surrounding of town. Therefore, the objective of this study is to assess Urban Expansion and its Impact on Peripheral Farming Communities: The Case of Assosa town, BGR, Ethiopia Thus the study investigated the impact of urban expansion on the peripheral community livelihood in case of Assosa town. Questionnaire, survey, focus group discussion and key informants interviews were tools of data collection from 160 sampled households living in sampled kebeles via systematic random sampling technique and judgmental technique for FGD and interview. The results of the study indicated that there is infrastructural improvement, socio economic growth, rapid population growth and also socio-economic problems related to urban expansion in studied area. There is great spatial and temporal land use land cover modification more towards to build up land uses. The livelihood condition of per-urban community changed to non-agricultural form but there are policy and strategy gaps of expropriating, compensating for affected community in ground implementation. Landholder expropriated should be recompensed for equal socio-economic beneficially from urbanization and further skill-oriented training for new livelihood strategy and also accessing credit and rehabilitating strategy were recommended for affected community livelihood.

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