scholarly journals Extrapolating Satellite-Based Flood Masks by One-Class Classification—A Test Case in Houston

2021 ◽  
Vol 13 (11) ◽  
pp. 2042
Author(s):  
Fabio Brill ◽  
Stefan Schlaffer ◽  
Sandro Martinis ◽  
Kai Schröter ◽  
Heidi Kreibich
Keyword(s):  
Urban Areas ◽  
Test Case ◽  
Minor Effect ◽  
High Quality ◽  
Imaging Geometry ◽  
Radar Sensors ◽  
Urban Structures ◽  
Complex Interactions ◽  
One Class Classifier ◽  
One Class Classification

Flood masks are among the most common remote sensing products, used for rapid crisis information and as input for hydraulic and impact models. Despite the high relevance of such products, vegetated and urban areas are still unreliably mapped and are sometimes even excluded from analysis. The information content of synthetic aperture radar (SAR) images is limited in these areas due to the side-looking imaging geometry of radar sensors and complex interactions of the microwave signal with trees and urban structures. Classification from SAR data can only be optimized to reduce false positives, but cannot avoid false negatives in areas that are essentially unobservable to the sensor, for example, due to radar shadows, layover, speckle and other effects. We therefore propose to treat satellite-based flood masks as intermediate products with true positives, and unlabeled cells instead of negatives. This corresponds to the input of a positive-unlabeled (PU) learning one-class classifier (OCC). Assuming that flood extent is at least partially explainable by topography, we present a novel procedure to estimate the true extent of the flood, given the initial mask, by using the satellite-based products as input to a PU OCC algorithm learned on topographic features. Additional rainfall data and distance to buildings had only minor effect on the models in our experiments. All three of the tested initial flood masks were considerably improved by the presented procedure, with obtainable increases in the overall κ score ranging from 0.2 for a high quality initial mask to 0.7 in the best case for a standard emergency response product. An assessment of κ for vegetated and urban areas separately shows that the performance in urban areas is still better when learning from a high quality initial mask.

scholarly journals The Geo-Social Model: A Transdisciplinary Approach to Flow-Type Landslide Analysis and Prevention

2021 ◽  
Vol 13 (5) ◽  
pp. 2501
Author(s):  
Valentina Acuña ◽  
Francisca Roldán ◽  
Manuel Tironi ◽  
Leila Juzam
Keyword(s):  
Urban Areas ◽  
Risk Perceptions ◽  
Risk Prevention ◽  
Social Model ◽  
Experimental Methodology ◽  
Landslide Risk ◽  
Sociocultural Environment ◽  
Flow Type ◽  
Complex Interactions ◽  
Municipal Level

Landslide disaster risks increase worldwide, particularly in urban areas. To design and implement more effective and democratic risk reduction programs, calls for transdisciplinary approaches have recently increased. However, little attention has been paid to the actual articulation of transdisciplinary methods and their associated challenges. To fill this gap, we draw on the case of the 1993 Quebrada de Macul disaster, Chile, to propose what we label as the Geo-Social Model. This experimental methodology aims at integrating recursive interactions between geological and social factors configuring landslide for more robust and inclusive analyses and interventions. It builds upon three analytical blocks or site-specific environments in constant co-determination: (1) The geology and geomorphology of the study area; (2) the built environment, encompassing infrastructural, urban, and planning conditions; and (3) the sociocultural environment, which includes community memory, risk perceptions, and territorial organizing. Our results are summarized in a geo-social map that systematizes the complex interactions between the three environments that facilitated the Quebrada de Macul flow-type landslide. While our results are specific to this event, we argue that the Geo-Social Model can be applied to other territories. In our conclusions, we suggest, first, that landslides in urban contexts are often the result of anthropogenic disruptions of natural balances and systems, often related to the lack of place-sensitive urban planning. Second, that transdisciplinary approaches are critical for sustaining robust and politically effective landslide risk prevention plans. Finally, that inter- and trans-disciplinary approaches to landslide risk prevention need to be integrated into municipal-level planning for a better understanding of—and prevention of—socio-natural hazards.

scholarly journals Urban Structure in Troubled Times: The Evolution of Principal and Secondary Core/Periphery Gaps through the Prism of Residential Land Values

2021 ◽  
Vol 13 (10) ◽  
pp. 5722
Author(s):  
Erez Buda ◽  
Dani Broitman ◽  
Daniel Czamanski
Keyword(s):  
Urban Areas ◽  
Hedonic Model ◽  
Land Values ◽  
Test Case ◽  
Urban Structure ◽  
Residential Real Estate ◽  
Residential Land ◽  
Ideal Candidate ◽  
Modern Cities ◽  
Spatial Level

The structure of modern cities is characterized by the uneven spatial distribution of people and activities. Contrary to economic theory, it is neither evenly distributed nor entirely monocentric. The observed reality is the result of various feedbacks in the context of the interactions of attraction and repulsion. Heretofore, there is no agreement concerning the means to measuring the dimensions of these interactions, nor the framework for explaining them. We propose a simple model and an associated method for testing the interactions using residential land values. We claim that land values reflect the attractiveness of each location, including its observable and unobservable characteristics. We extract land values from prices of residences by applying a dedicated hedonic model to extensive residential real estate transaction data at a detailed spatial level. The resulting land values reflect the attractiveness of each urban location and are an ideal candidate to measure the degree of centrality or peripherality of each location. Moreover, assessment of land values over time indicates ongoing centralization and peripheralization processes. Using the urban structure of a small and highly urbanized country as a test case, this paper illustrates how the dynamics of the gap between central and peripheral urban areas can be assessed.

scholarly journals Māori Urban Migrations and Identities, ‘Ko Ngā Iwi Nuku Whenua’: A study of Urbanisation in the Wellington Region during the Twentieth Century

2021 ◽  
Author(s):  
◽  
Erin Keenan
Keyword(s):  
Twentieth Century ◽  
Urban Areas ◽  
Urban Migration ◽  
World War ◽  
Historical Sources ◽  
The Past ◽  
Complex Interactions ◽  
The Subject ◽  
The Many ◽  
Migration Experiences

<p>Māori urbanisation and urban migrations have been the subject of much discussion and research, especially following World War Two when Māori individuals, whānau and communities increasingly became residents of towns and cities that were overwhelmingly Pākehā populated. However, Māori urbanisation experiences and urban migrations are difficult topics to address because kaumātua are reluctant to discuss ‘urban Māori’, especially considering its implications for Māori identities. The original contribution this thesis makes to histories of Māori urban migrations is that it explores these and other understandings of urbanisations to discover some of their historical influences. By discussing urbanisations directly with kaumātua and exploring historical sources of Māori living in, and moving to, the urban spaces of Wellington and the Hutt Valley through the twentieth century, this thesis is a ‘meeting place’ for a range of perspectives on the meanings of urbanisations from the past and the present. Although urbanisation was an incredible time of material change for the individuals and whānau who chose to move into cities such as Wellington, the histories of urban migration experiences exist within a scope of Māori and iwi worldviews that gave rise to multiple experiences and understandings of urbanisations. The Wellington region is used to show that Māori in towns and cities used Māori social and cultural forms in urban areas so that they could, through the many challenges of becoming urban-dwelling, ensure the persistence of their Māoritanga. Urbanisations also allowed Māori to both use traditional identities in urban areas, as well as develop new relationships modelled on kinship. The Ngāti Pōneke community is used as an example of the complex interactions between these identities and how many Māori became active residents in but not conceptually ‘of’ cities. As a result, the multiple and layered Māori identities that permeate throughout Māori experiences of the present and the past are important considerations in approaching and discussing urbanisations. Urban Māori communities have emphasised the significance of varied and layered Māori identities, and this became particularly pronounced through the Māori urban migrations of the twentieth century.</p>

scholarly journals AN INTERACTIVE DESIGN TOOL FOR URBAN PLANNING USING THE SIZE OF THE LIVING SPACE AS UNIT OF MEASUREMENT

2019 ◽  
Vol XLII-4/W15 ◽  
pp. 3-10
Author(s):  
F. G. García González ◽  
G. Agugiaro ◽  
R. Cavallo
Keyword(s):  
Urban Planning ◽  
Urban Areas ◽  
Design Parameter ◽  
Open Data ◽  
Design Tool ◽  
Test Case ◽  
Custom Made ◽  
Common Unit ◽  
Unit Of Measurement ◽  
Average Size

<p><strong>Abstract.</strong> In urban planning, a common unit of measurement for population density is the number of households per hectare. However, the actual size of the households is seldom considered, neither in 2D nor in 3D. This paper proposes a method to calculate the average size of the household in existing urban areas from available open data and to use it as a design parameter for new urban development. The proposed unit of measurement includes outdoor and indoor spaces, the latter comprising both residential and non-residential spaces. As a test case, a to-be-planned neighbourhood in Amsterdam, called Sloterdijk One, was chosen. First, the sizes of “typical” households, as well as a series of KPIs, were computed in existing neighbourhoods of Amsterdam, based on their similarities with the envisioned Sloterdijk One plan. Successively, the resulting size of the household was used as a design parameter in a custom-made tool to generate semi-automatically several design proposals for Sloterdijk One. Additionally, each proposal can be exported as a CityGML model and visualised using web-based virtual globes, too. Significant differences among the resulting proposals based on this new unit of measurement were encountered, meaning that the average size of a household plays indeed a major role.</p>

scholarly journals Valuing Urban Tropical River Recreation Attributes Using Choice Experiments

2016 ◽  
Vol 6 (2) ◽  
pp. 128 ◽  
Author(s):  
Luis Santiago ◽  
John Loomis ◽  
Alisa V. Ortiz ◽  
Ariam L. Torres
Keyword(s):  
Urban Areas ◽  
Water Clarity ◽  
Choice Experiments ◽  
Economic Benefits ◽  
Public Access ◽  
High Quality ◽  
Scarce Resources ◽  
Marginal Values ◽  
River Recreation ◽  
In Parenthesis

While providing public access to rivers in urban areas is a first step, maintaining a high quality recreation experience can be expensive. Knowing the economic benefits of high quality recreation may help recreation managers in justifying budget increases and define priorities during a time of scarce resources. To provide that information we have conducted urban river recreation valuation using Choice Experiments (CE). We value user defined recreation attribute improvements for the following: reducing the presence of trash, increasing water clarity, reducing crowds and increasing vegetation. We also tested whether pro-environmental attitudes and behaviors influence visitors’ Willingness to Pay (WTP) for improvements in environmental attributes. Three of the four attribute improvements were statistically significant (marginal values are provided in parenthesis): reduction of trash ($173), improving water clarity ($52), and reducing crowding ($28). The results can help managers justify improved trash removal and littering enforcement strategies, and advocate improvement of water quality by means of enacting and enforcing more strict regulations on littering, off-roading use, gravel pit discharges, and maximum visitation levels.

scholarly journals One-Class Classification with Extreme Learning Machine

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Qian Leng ◽  
Honggang Qi ◽  
Jun Miao ◽  
Wentao Zhu ◽  
Guiping Su
Keyword(s):  
Neural Network ◽  
Extreme Learning Machine ◽  
Classification Problem ◽  
Traditional Learning ◽  
Learning Speed ◽  
One Class Classifier ◽  
Learning Machine ◽  
Hidden Layer ◽  
One Class Classification ◽  
Network Approaches

One-class classification problem has been investigated thoroughly for past decades. Among one of the most effective neural network approaches for one-class classification, autoencoder has been successfully applied for many applications. However, this classifier relies on traditional learning algorithms such as backpropagation to train the network, which is quite time-consuming. To tackle the slow learning speed in autoencoder neural network, we propose a simple and efficient one-class classifier based on extreme learning machine (ELM). The essence of ELM is that the hidden layer need not be tuned and the output weights can be analytically determined, which leads to much faster learning speed. The experimental evaluation conducted on several real-world benchmarks shows that the ELM based one-class classifier can learn hundreds of times faster than autoencoder and it is competitive over a variety of one-class classification methods.

scholarly journals The City of Tomorrow from… the Data of Today

2020 ◽  
Vol 9 (9) ◽  
pp. 554
Author(s):  
Giorgio Agugiaro ◽  
Francisco González ◽  
Roberto Cavallo
Keyword(s):  
Urban Areas ◽  
Open Data ◽  
Physical Space ◽  
Design Parameters ◽  
Computer Assisted ◽  
Test Case ◽  
Living Space ◽  
Common Unit ◽  
Average Size ◽  
The City

In urban planning, a common unit of measure for housing density is the number of households per hectare. However, the actual size of the physical space occupied by a household, i.e., a dwelling, is seldom considered, neither in 2D nor in 3D. This article proposes a methodology to estimate the average size of a dwelling in existing urban areas from available open data, and to use it as one of the design parameters for new urban-development projects. The proposed unit of measure, called “living space”, includes outdoor and indoor spaces. The idea is to quantitatively analyze the city of today to help design the city of tomorrow. First, the “typical”-dwelling size and a series of Key Performance Indicators are computed for all neighborhoods from a semantic 3D city model and other spatial and non-spatial datasets. A limited number of neighborhoods is selected based on their similarities with the envisioned development plan. The size of the living space of the selected neighborhoods is successively used as a design parameter to support the computer-assisted generation of several design proposals. Each proposal can be exported, shared, and visualized online. As a test case, a to-be-planned neighborhood in Amsterdam, called “Sloterdijk One”, has been chosen.

Methodological Dimensions of Delineating Peri-urban Areas: The Case of Kolkata Metropolis

2020 ◽  
Vol 11 (2) ◽  
pp. 183-194
Author(s):  
Dinabandhu Mondal ◽  
Sucharita Sen
Keyword(s):  
Rural Areas ◽  
Urban Areas ◽  
Urban Spaces ◽  
The Past ◽  
Social Transitions ◽  
Complex Interactions ◽  
Metropolitan Cities ◽  
Municipal Boundaries ◽  
The City ◽  
Complex Characters

In the past few decades, due to urbanization and spatial expansion of cities beyond their municipal boundaries, complex interactions between the city and its surrounding rural areas have occurred, resulting in the formation of peri-urban spaces or zones of transition. There is a plurality of definitions for these peri-urban spaces, due to their diverse character in terms of land and water use, livelihood shifts, demographic and social transitions. Most peri-urban areas, specifically those around large metropolitan cities, are increasingly assuming complex characters, which call for governance structures beyond rural–urban binaries. For any administrative intervention of a serious nature in peri-urban areas, a standard methodology for demarcation of these spaces is required. This article is an attempt to develop and apply such a methodology beyond the existing ones, using government sources of data, in the case of Kolkata Metropolis. This article uses socio-economic and land-use characteristics to achieve this objective. It finds that peri-urban spaces do not necessarily develop uniformly around the city; instead, they are fragmented and could be located both near or relatively far from urban areas.

scholarly journals High-quality observation of surface imperviousness for urban runoff modelling using UAV imagery

2015 ◽  
Vol 19 (10) ◽  
pp. 4215-4228 ◽  
Author(s):  
P. Tokarczyk ◽  
J. P. Leitao ◽  
J. Rieckermann ◽  
K. Schindler ◽  
F. Blumensaat
Keyword(s):  
Land Use ◽  
High Resolution ◽  
Surface Runoff ◽  
Urban Areas ◽  
Image Data ◽  
Aerial Images ◽  
Urban Drainage ◽  
High Quality ◽  
Modern Classification

Abstract. Modelling rainfall–runoff in urban areas is increasingly applied to support flood risk assessment, particularly against the background of a changing climate and an increasing urbanization. These models typically rely on high-quality data for rainfall and surface characteristics of the catchment area as model input. While recent research in urban drainage has been focusing on providing spatially detailed rainfall data, the technological advances in remote sensing that ease the acquisition of detailed land-use information are less prominently discussed within the community. The relevance of such methods increases as in many parts of the globe, accurate land-use information is generally lacking, because detailed image data are often unavailable. Modern unmanned aerial vehicles (UAVs) allow one to acquire high-resolution images on a local level at comparably lower cost, performing on-demand repetitive measurements and obtaining a degree of detail tailored for the purpose of the study. In this study, we investigate for the first time the possibility of deriving high-resolution imperviousness maps for urban areas from UAV imagery and of using this information as input for urban drainage models. To do so, an automatic processing pipeline with a modern classification method is proposed and evaluated in a state-of-the-art urban drainage modelling exercise. In a real-life case study (Lucerne, Switzerland), we compare imperviousness maps generated using a fixed-wing consumer micro-UAV and standard large-format aerial images acquired by the Swiss national mapping agency (swisstopo). After assessing their overall accuracy, we perform an end-to-end comparison, in which they are used as an input for an urban drainage model. Then, we evaluate the influence which different image data sources and their processing methods have on hydrological and hydraulic model performance. We analyse the surface runoff of the 307 individual subcatchments regarding relevant attributes, such as peak runoff and runoff volume. Finally, we evaluate the model's channel flow prediction performance through a cross-comparison with reference flow measured at the catchment outlet. We show that imperviousness maps generated from UAV images processed with modern classification methods achieve an accuracy comparable to standard, off-the-shelf aerial imagery. In the examined case study, we find that the different imperviousness maps only have a limited influence on predicted surface runoff and pipe flows, when traditional workflows are used. We expect that they will have a substantial influence when more detailed modelling approaches are employed to characterize land use and to predict surface runoff. We conclude that UAV imagery represents a valuable alternative data source for urban drainage model applications due to the possibility of flexibly acquiring up-to-date aerial images at a quality compared with off-the-shelf image products and a competitive price at the same time. We believe that in the future, urban drainage models representing a higher degree of spatial detail will fully benefit from the strengths of UAV imagery.

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