Assessing The Quality of Water Depth Derived From Volunteered Geographic Information (VGI) For Flood Monitoring. A Case Study of Hurricane Harvey In Harris County, Texas

2021 ◽  
Author(s):  
Abdullatif Alyaqout ◽  
T. Edwin Chow ◽  
Alexander Savelyev
Keyword(s):  
Water Depth ◽  
Temporal Distribution ◽  
Volunteered Geographic Information ◽  
Temporal Variations ◽  
Geographic Information ◽  
Text Messages ◽  
Quality Of Water ◽  
Significant Difference ◽  
Flood Monitoring

Abstract The primary objectives of this study are to 1) assess the quality of each volunteered geographic information (VGI) data modality (text, pictures, and videos), and 2) evaluate the quality of multiple VGI data sources, especially the multimedia that include pictures and videos, against synthesized water depth (WD) derived from remote sensing (RS) and authoritative data (e.g. stream gauges and depth grids). The availability of VGI, such as social media and crowdsourced data, empowered the researchers to monitor and model floods in near-real-time by integrating multi-sourced data available. Nevertheless, the quality of VGI sources and its reliability for flood monitoring (e.g. WD) is not well understood and validated by empirical data. Moreover, existing literature focuses mostly on text messages but not the multimedia nature of VGI. Therefore, this study measures the differences in synthesized WD from VGI modalities in terms of (1) spatial and (2) temporal variations, (3) against WD derived from RS, and (4) against authoritative data including (a) stream gauges and (b) depth grids. The results of the study show that there are significant differences in terms of spatial and temporal distribution of VGI modalities. Regarding VGI and RS comparison, the results show that there is a significant difference in WD between VGI and RS. In terms of VGI and authoritative data comparison, the analysis revealed that there is no significant difference in WD between VGI and stream gauges, while there is a significant difference between the depth grids and VGI.

scholarly journals The Spatial-Comprehensiveness (S-COM) Index: Identifying Optimal Spatial Extents in Volunteered Geographic Information Point Datasets

2020 ◽  
Vol 9 (9) ◽  
pp. 497
Author(s):  
Haydn Lawrence ◽  
Colin Robertson ◽  
Rob Feick ◽  
Trisalyn Nelson
Keyword(s):  
Social Media ◽  
Data Quality ◽  
Spatial Scales ◽  
Volunteered Geographic Information ◽  
Geographic Information ◽  
Quality Metric ◽  
Fine Grained ◽  
Multi Scale ◽  
Feasible Study

Social media and other forms of volunteered geographic information (VGI) are used frequently as a source of fine-grained big data for research. While employing geographically referenced social media data for a wide array of purposes has become commonplace, the relevant scales over which these data apply to is typically unknown. For researchers to use VGI appropriately (e.g., aggregated to areal units (e.g., neighbourhoods) to elicit key trend or demographic information), general methods for assessing the quality are required, particularly, the explicit linkage of data quality and relevant spatial scales, as there are no accepted standards or sampling controls. We present a data quality metric, the Spatial-comprehensiveness Index (S-COM), which can delineate feasible study areas or spatial extents based on the quality of uneven and dynamic geographically referenced VGI. This scale-sensitive approach to analyzing VGI is demonstrated over different grains with data from two citizen science initiatives. The S-COM index can be used both to assess feasible study extents based on coverage, user-heterogeneity, and density and to find feasible sub-study areas from a larger, indefinite area. The results identified sub-study areas of VGI for focused analysis, allowing for a larger adoption of a similar methodology in multi-scale analyses of VGI.

scholarly journals ASSESSMENT OF COMPLETENESS AND POSITIONAL ACCURACY OF LINEAR FEATURES IN VOLUNTEERED GEOGRAPHIC INFORMATION (VGI)

2015 ◽  
Vol XL-1-W5 ◽  
pp. 169-174
Author(s):  
M. Eshghi ◽  
A. A. Alesheikh
Keyword(s):  
Spatial Data ◽  
Volunteered Geographic Information ◽  
Geographic Information ◽  
Positional Accuracy ◽  
Linear Feature ◽  
Almost All ◽  
Information Collecting ◽  
Correct Data ◽  
Official Data

Recent advances in spatial data collection technologies and online services dramatically increase the contribution of ordinary people to produce, share, and use geographic information. Collecting spatial data as well as disseminating them on the internet by citizens has led to a huge source of spatial data termed as Volunteered Geographic Information (VGI) by Mike Goodchild. Although, VGI has produced previously unavailable data assets, and enriched existing ones. But its quality can be highly variable and challengeable. This presents several challenges to potential end users who are concerned about the validation and the quality assurance of the data which are collected. Almost, all the existing researches are based on how to find accurate VGI data from existing VGI data which consist of a) comparing the VGI data with the accurate official data, or b) in cases that there is no access to correct data; therefore, looking for an alternative way to determine the quality of VGI data is essential, and so forth. In this paper it has been attempt to develop a useful method to reach this goal. In this process, the positional accuracy of linear feature of Iran, Tehran OSM data have been analyzed.

scholarly journals The Establishment of Experimental Green Roofs

2018 ◽  
Vol 66 (1) ◽  
pp. 43-48
Author(s):  
Věra Hubačíková ◽  
Lenka Filipová ◽  
Petr Pelikán
Keyword(s):  
Green Roofs ◽  
Water Runoff ◽  
University Campus ◽  
Retention Efficiency ◽  
Quality Of Water ◽  
Significant Difference ◽  
Different Types ◽  
Rainwater Management ◽  
Experimental Plots

The aim of the work was establishment of research green roofs on Mendel University in Brno. The experimental green roofs were established in August 2015 and it is based on current issues of rainwater management and the quality of storm water launched into recipients or sewage system. There is a valid legislation addressing the management of rainwater in environment – decree no. 268/2009, Coll., and decree no. 269/2009, Coll. Four experimental plots were created and placed in Mendel University Campus. It was hypothesized that different types of experimental plots will result in different amount of retained water and in different quality of water runoff. Resulting hypotheses proved statistically significant difference between the height of rainfall and runoff height on individual types of green roofs. In addition, it was shown that the different types of roofs prove statistically significant difference in the ability to reduce runoff (retention efficiency).

An Integrated Method for Assessing the Text Content Quality of Volunteered Geographic Information in Disaster Management

2017 ◽  
Vol 9 (2) ◽  
pp. 1-17
Author(s):  
Kuo-Chih Hung ◽  
Mohsen Kalantari ◽  
Abbas Rajabifard
Keyword(s):  
Disaster Management ◽  
Volunteered Geographic Information ◽  
Geographic Information ◽  
Content Quality ◽  
Integrated Method ◽  
Needed Information ◽  
Text Content ◽  
Flooding Events

Volunteered geographic information (VGI) has the potential to provide much-needed information for emergency management stakeholders. However, stakeholders often lack scalability to identify useful and high-quality text content from the often-overwhelming amount of information. To solve this problem, most studies have concentrated on using text-related features in supervised learning models to classify text contents. This article proposes an assumption that the geographic attributes of VGI can be integrated into the model as features for enhancing the model's performance. To evaluate this assumption, the authors developed a case study based on VGI collected from two flooding events in Brisbane. They validated the accuracy of associated geographic coordinates and defined the geographic features relevant to the flood phenomenon. From their experiments, model based on this integrated method can have better performance in comparison with the model trained from the text-related features. The results suggest great potential for using the integrated method to harvest useful VGI for the needs of disaster management.

scholarly journals Using Geographic Information System (GIS) to estimate the volume of water for Al Dammam unconfined Aquifer within Al Salman basin, Al- Muthana Governorate, South West Iraq

2019 ◽  
pp. 1478-1485
Author(s):  
Osamah N. Al-Sheikh ◽  
Ayser M. Al-Shamma’a
Keyword(s):  
Information System ◽  
Geographic Information System ◽  
Unconfined Aquifer ◽  
Geographic Information ◽  
Quality Of Water ◽  
Digital Elevation ◽  
Automate Calculation ◽  
West Iraq ◽  
Flow Map

The groundwater represents the main source of water in the study area due to lack of surface water. The Dammam unconfined aquifer represents the main aquifer in the study area and Southern desert because of the regional extent, the quantity and quality of water. Many groundwater wells have been drilled in the study area to coverage the huge demand of water for agricultural purposes. The Geographic Information System (GIS) was used to estimate the volume of water which calculated (25.6964 × 109 m3) within the study area , automate calculation of the area of Al Salman basin using digital elevation models, derive the thickness maps of AlDammam unconfined aquifer from Key holes (KH) and Bore holes (BH), draw the groundwater head and flow map in the study area. Such data derived from GIS can help authorities and researchers for groundwater management and further development within the study area.

Quality Evaluation of Volunteered Geographic Information

Crowdsourcing ◽  
2019 ◽  
pp. 1173-1201
Author(s):  
Hongyu Zhang ◽  
Jacek Malczewski
Keyword(s):  
Quality Evaluation ◽  
Evaluation Process ◽  
Volunteered Geographic Information ◽  
Geographic Information ◽  
Positional Accuracy ◽  
Product Selection ◽  
Geographic Space ◽  
Large Size

A large amount of crowd-sourced geospatial data have been created in recent years due to the interactivity of Web 2.0 and the availability of Global Positioning System (GPS). This geo-information is typically referred to as volunteered geographic information (VGI). OpenStreetMap (OSM) is a popular VGI platform that allows users to create or edit maps using GPS-enabled devices or aerial imageries. The issue of quality of geo-information generated by OSM has become a trending research topic because of the large size of the dataset and the inapplicability of Linus' Law in a geospatial context. This chapter systematically reviews the quality evaluation process of OSM, and demonstrates a case study of London, Canada for the assessment of completeness, positional accuracy and attribute accuracy. The findings of the quality evaluation can potentially serve as a guide of cartographic product selection and provide a better understanding of the development of OSM quality over geographic space and time.

Quality Evaluation of Volunteered Geographic Information

2017 ◽  
pp. 19-46 ◽  
Author(s):  
Hongyu Zhang ◽  
Jacek Malczewski
Keyword(s):  
Quality Evaluation ◽  
Evaluation Process ◽  
Volunteered Geographic Information ◽  
Geographic Information ◽  
Positional Accuracy ◽  
Product Selection ◽  
Geographic Space ◽  
Large Size

A large amount of crowd-sourced geospatial data have been created in recent years due to the interactivity of Web 2.0 and the availability of Global Positioning System (GPS). This geo-information is typically referred to as volunteered geographic information (VGI). OpenStreetMap (OSM) is a popular VGI platform that allows users to create or edit maps using GPS-enabled devices or aerial imageries. The issue of quality of geo-information generated by OSM has become a trending research topic because of the large size of the dataset and the inapplicability of Linus' Law in a geospatial context. This chapter systematically reviews the quality evaluation process of OSM, and demonstrates a case study of London, Canada for the assessment of completeness, positional accuracy and attribute accuracy. The findings of the quality evaluation can potentially serve as a guide of cartographic product selection and provide a better understanding of the development of OSM quality over geographic space and time.

scholarly journals Study on the Quality of Water in Some Streams of Cauvery River

2008 ◽  
Vol 5 (2) ◽  
pp. 377-384 ◽  
Author(s):  
Abida Begum ◽  
Harikrishnarai
Keyword(s):  
Dissolved Oxygen ◽  
Small Scale ◽  
Cauvery River ◽  
Aquatic Life ◽  
Discharge Point ◽  
Quality Of Water ◽  
Significant Difference ◽  
Effluent Discharge ◽  
The Impact

The quality of water in four streams of Cauvery River in Mandya District, where many small scale sugar and brewery distilleries are located, was analysed. Sampling was carried out from four streams designated as station 1 (upstream of effluent discharge point), station 2 (effluent discharge point) and station 3 (downstream of effluent discharge) station 4 (fresh water stream) to assess the impact of effluent on the water quality. The river water composition is increasingly dominated by Na and Cl in the downstream region of the river, indicating the influence of airborne salts with oceanic affinities. Significant spatial variation was observed in water level, transparency, turbidity, depth, dissolved oxygen, colour, biochemical oxygen demand, nitrate, nitrite and total hydrocarbon among the physiochemical parameters of the study stations. Aposterioritest revealed that station 2 & 3 were the cause of the significant difference. The dissolved oxygen level in stations 2 & 3 was lower than 5.0mg/L, which is recommended minimum allowable limit for aquatic life. About 7 rotifer species in large amount recorded in this study were encountered in station 1, 7 in station 2 & 3 while 12 species in station 4. The overall density of rotifers in the four stations was significantly different. Aposterioricomparison revealed that station 2 & 3 are the cause of the significant difference. The Branchionus angularis rotifers, which dominated the community, were found to tolerate the effluent effect in station 2&3, and showed remarkable recovery in the downstream station 4. Low faunal diversity and negative impact on the biotic and abiotic environment was experienced in station 2 & 3 throughout the duration of sampling because of the brewery effluent discharged directly into these two Streams.

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