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1 Introduction

With recent advancements in wireless communications and Internet technology during the last decade, it is promising to develop many citizen-centric new applications and services in various fields including spatial information technology. The users of geospatial technology have started to use online GIS (geographic information system) for a variety of applications by using web services and online data repositories. Internet today has emerged as one of the most suitable and quickest means for accessing, analyzing, displaying, and transmitting the geographical information and geographic knowledge. It is perhaps the only means which maximizes the potential of GIS data and software application for wider and easier access of geographical data to the planners and decision-makers. The World Wide Web, FTP (file transfer protocol), and HTTP programs make it convenient to access and transfer data files across the Internet. Internet technology in conjunction with GIS today in crisis situations allows geospatial information coming from multiple sources to be integrated in real time, interactively accessed and visualized to generate accurate and quick actionable information for emergency response teams coordinating the activity (Mansourian et al., 2005). Today the distributed and heterogeneous resources and data services can be accessed through a centralized and uniform interface using GIS-based web portals (Karnatak et al. 2007, 2012). Considering the different types of disasters varying from natural to man-made having diverse data requirements, a single GIS web service may not be sufficient enough to handle all requirements, and therefore specifically the web GIS-based portals available in the Internet are generally customized and developed for a particular theme keeping in mind a specific class of user(s). The availability of international data and information service standards published by the Open Geospatial Consortium (OGC) is playing an important role to achieve interoperability in data and information sharing. GIS service standards published by OGC are based on distributed service-oriented architectures (SOA). Such systems unify distributed services through a message-oriented architecture by using Simple Object Access Protocol (SOAP). The data and information services available through web portal applications have great scope of its massive utilization at user’s end. Many GIS-based plans for a variety of applications can be developed using available GIS-based web services (also known as Geoweb services) and online data repositories. Some of the major advantages of Geoweb services and online data repositories include dynamic and updated data, real-time and multiuser access, and development of user-defined applications using mashup architecture (Karnatak et al. 2012). This approach is quite useful for the applications where real-time dynamic data is required for planning and decision-making such as disaster or emergency management.

Due to the large spatial extent of disasters affecting several people across the countries, geospatial technology today finds a wider acceptance and has become an important tool for decision-making process. The traditional desktop GIS-based disaster response to an emergency situation and relief operations using traditional maps has been transformed completely, with the evolution of Internet technology. Web-based GIS technologies today allow collaborative environment to access, process, and integrate real-time data flow from various sources and a number of users to generate actionable products and respond to an emergency situation much better than before. Today when the disasters have become more intense and severe, the online data repositories and information services can play a critical role in supporting all phases of disaster monitoring and mitigation. The increasing availability of free satellite imagery (like Sentinel data), GIS thematic maps (OpenStreetMap), GIS software (QGIS), and theme-specific hazard modeling software (HEC-RAS) to analyze the data offers considerable potential to decision-makers and planners to take appropriate informed decision in times of crisis. The present technology allows to access data and information from a variety of sources and also integrate it to one common platform for user-defined applications. This chapter presents a technological overview of Geoweb service and online data repositories and a list of popular open online resources and also demonstrates a case study for effective utilization of these services in flood disaster monitoring and mitigation.

2 Geoweb Services and Online Data Repositories

Advancements in information and communication technologies (ICT) have facilitated a new way for sharing and dissemination of geospatial data and information. The online data repositories and web applications are providing various means of data access by using the Internet and related technologies. Today, the users of geospatial data and information can use Internet platform for various geoscientific activities such as spatial queries, geo-visualization, and simple to complex computations for decision-making and virtual reality. Considering the importance of spatial data for humanitarian response during natural disasters, many agencies and individuals are hosting their data sets online, which has enhanced the outreach of geospatial data manyfold. These open geo-data sets can be used for various thematic applications either as a Geoweb service or as a data product(s).

The service-oriented architecture (SOA) and related technologies for distributed GIS applications are providing interoperable platform for data sharing and disemintions. The SOA-based software systems provide independent building blocks that jointly represent the software application environment (Karnatak et al. 2012). One of the unique features of SOA-based software applications is to set up complete autonomy among different service components which is important for interoperability. The most popular SOA-based web services implementations are based on XML. The Extensible Markup Language (XML) is a markup language developed by W3C to define the set of rules for encoding the documents in plain text format. The XML is used to define the data and information and is also known as data definition language. The outcomes of XML are presented as Hypertext Markup Language (HTML) document which is known as data presentation language. The SOA architecture has three basic components, i.e., a provider, a requester, and a broker (Fig. 23.1). The provider is the owner or publisher of the service, typically the client or user is a requester, and the broker is the component which maintains the registry of available services as catalogue. The interaction between the above three components is represented as three operations, i.e., publish, find, and bind.

Fig. 23.1
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Service-oriented architecture

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The SOA-based web services for geospatial data, process, encoding, and other spatial operations are very important to achieve interoperability in data and information sharing. The web service standards for geospatial and data and process are designed and developed by the Open Geospatial Consortium (OGC). OGC is an international standards organization which was founded in 1994 with the objectives of development, promotion, and harmonization of open geospatial data standards.

The web services published by OGC for geospatial data and process can also be represented as Geoweb services. The Geoweb services published by OGC can be grouped into six major categories, i.e., catalogue or registry services, processing or analytical services, encoding services, data or geo-data services, portrayal or visualization services, and other services. These services have been briefly described below:

2.1 Catalogue or Registry Services

This category of services is designed to classify, register, describe, and search the services by a user or a program. Some of the examples are CS Core, CS-WebRIM, and CS-W 19115/19119.

2.2 Data Processing Services

The processing services are designed to publish processes such as arithmetic operations, overlay operations, algorithms, etc. These are typically providing the capabilities of processing or transforming data-based user-defined parameters (Sahina and Gumusay 2008). The examples of WPS are Web Processing Service (WPS), Web Coverage Processing Service (WCPS), and Coordinate Transformation Service (CTS).

2.3 Encoding Services

Encoding is the process of putting a sequence of characters into a special format which is desired by the user for transmission or storage purposes. In GIS, encoding plays a critical role while defining the cartographic principles in spatial outputs. Typical example could be symbology to present legends in a map. Most popular encoding standards publish by OGC are Geography Markup Language (GML), Styled Layer Descriptor (SLD), KML, CityGML, etc.

2.4 Geo-data Services

The data services are designed to share the geospatial data (vector and raster) without any data loss. These services allow full or partial access of data based on user-defined area of interest (AOI). Some of the examples of OGC data services are Web Feature Service (WFS), Web Coverage Service (WCS), Sensor Observation Services (SOS), etc.

2.5 Visualization Services

The visualization services offered by OGC are typically for geo-visualization as background or overlay layer (s). These services also provide data with cartographic representations. Examples are Web Map Services (WMS) and Web Map Tile Services (WMTS).

2.6 Application or Job-Oriented Services

These services are designed for specific application or data requirements. Some of the examples include GeoXACML and GeoRSS.

The open online data repositories and Geoweb services are providing data and information by using web service standards published by OGC. The websites are available either as geo-portal or online data archive. The web portals are dynamic web applications which serve data and information to its user(s) by using database server technology. In web portal applications, the data is accessed and processed using an additional middle tier at server end using any web programming language such as PHP, C#, JAVA, Python, etc. This middle tier is also known as business logic or application server. In case of GIS data, the database servers host the raster and vector data in addition to attribute data sets in a database server. The geo-portals are developed based on GIS servers which are also known as map server(s). The GIS servers typically act as middle tier in software application architecture to make geospatial data compatible with Internet client software applications such as web browsers. Some of the popular geo-portal applications, online data repositories, early warning portals, and data analysis tools are provided in Tables 23.1, 23.2, 23.3 and 23.4. The list provided is not exhaustive, and accessing of datasets or application through these portals may require registration and proper acknowledgment. The users are therefore advised to read the data policy and data sharing policies.

Table 23.1 Popular geoportal applications
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Table 23.2 Portal providing alerts, online data repository, and natural disaster-related information
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Table 23.3 Other online data repositories useful for general research and analysis including disaster mitigation
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Table 23.4 Tools and models available in open domain for disaster analysis
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3 Case Study: Utilization of Online Data Repositories

This section attempts to demonstrate utilization of various online data repositories and tools which could be accessed openly and will be helpful for decision-makers and planners for taking measures to mitigate the impact of flood disaster. The main objective of the section is only to give a basic idea of how resources available from various sources in open domain can be integrated for informed decision-making. Figure 23.2 shows the various portals providing online data repositories, visualization, and analysis tools which can be accessed right from disaster watch stage to preparedness stage and finally flood disaster response phase.

Fig. 23.2
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Portals and online data repositories for flood disaster event

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For a flood disaster event, the disaster manager needs to keep a watch on the cloud persistence, heavy rainfall event, and rising river water levels which indicate the possibility of the event. If there is a possibility of the event to occur, disaster manager needs to have some preparedness measures in place, like which areas are likely to get inundated based on the historic inundation and identification of low-lying areas based on digital elevation model (DEM) analysis. Finally in case if the flood disaster occurs, the disaster needs to be mapped and monitored to know the spatial extent of inundation, transport network submerged, and villages marooned. In subsequent section the above-explained requirements for the three stages (watch, preparedness, and response) are explained with the help of various online data repositories and tools considering a heavy rainfall likely to occur over Srinagar, Jammu, and Kashmir which could cause floods in the Srinagar Valley.

3.1 Disaster Watch

Heavy continuous rainfall could trigger floods, and therefore advance information on heavy rainfall forecast for the next coming days is essential for taking appropriate mitigation measures. The Meteorological and Oceanographic Satellite Data Archival Centre (MOSDAC) at the Space Applications Centre (ISRO) provides experimental mesoscale weather forecasts in real time using WRF model (Shah et al. 2010) which can be downloaded through http://www.mosdac.gov.in/external/order-data. The WRF data which is in netcdf file format can be processed, analyzed, and visualized using freely available Grid Analysis and Display System (GrADS) software accessible through http://cola.gmu.edu/grads/downloads.php. MOSDAC portal itself allows visualization of WRF-related parameters (rainfall, temperature, relative humidity, cloud fraction, etc.) in GIS environment (http://www.mosdac.gov.in/weather_forecast/index.jsp?param=hrf_24) which can be seen with base layers superimposed, the heavy rainfall and cloud fraction forecast for the next 3 days can give an understanding about areas likely to experience flood in coming days (Figs. 23.3 and 23.4). Further INSAT-3D images which are available every half hourly from MOSDAC (http://www.mosdac.gov.in/data/servlet/Image3d?imagename=3DIMG*_L1C_ASIA_MER_IR1.jpg) and also IMD (http://satellite.imd.gov.in/img/animation3d/3Dasiasec_ir1_3d.htm) as individual images and also as animation can help in monitoring the movement and persistence of cloud cover over the interested region (Fig. 23.5). Due to heavy rainfall in the upstream catchment areas, the water level in the rivers also starts rising which can be monitored using the Central Water Commission (CWC) gauge station information on current level and previous water level accessed through http://www.india-water.gov.in/eSWIS-MapViewer/. The portal provides information in spatial format as well as in hydrograph format. Figure 23.6 shows that by clicking on the gauge station, information on the warning level, danger level, highest flood level (HFL), date of occurrence of HFL, present water level, and trend could be observed.

Fig. 23.3
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MOSDAC portal showing daily rainfall (mm) accumulation forecast

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Fig. 23.4
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MOSDAC portal showing daily cloud conditions forecast

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Fig. 23.5
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IMD portal showing cloud persistence available from INSAT-3D images

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Fig. 23.6
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CWC portal showing river gauge data for Sangam, Jammu, and Kashmir station

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3.2 Disaster Preparedness

With the basic information obtained from rainfall forecast, cloud persistence, and gauge height by accessing various online portals, disaster manager gets a fair idea about the likely scenario for flood event to take place in advance can be made and can help to make plans for preparedness before the event actually happens. Knowing that there is a possibility of flood event, the decision-maker needs to have some idea about the regions that are likely to get flooded to take precautionary measures on ground for safe evacuation of the inhabitants staying in those areas. ISRO DMS services in tandem with ISRO’s Geo-portal, Bhuvan, in public domain are a unique demonstration of EO data and geospatial technology utilization for visualization, understanding, effective planning, and decision-making for disaster management. Bhuvan supports management of disasters like cyclone, floods, landslides, earthquakes, forest fire, and drought, which is useful for various phases of disaster management including preparedness and response. Figure 23.7 shows historic flood inundation layers extracted from multi-temporal (08–23 Sept. 2014) satellite images during Srinagar floods in Jammu and Kashmir during September 2014 and available through Bhuvan Disaster Services (http://bhuvan-noeda.nrsc.gov.in/disaster/disaster/disaster.php#). This information can be visualized together with various other thematic information available with Bhuvan like land use and administrative boundaries to gain insight about areas which have experienced flood in past and also the land use that will get affected in those areas and also visualize the terrain with help of Bhuvan 3D. In addition to the available historic inundation, low-lying areas with the help of freely available digital elevation data of Cartosat DEM (~30 m) from Bhuvan (http://bhuvan.nrsc.gov.in/data/download/index.php) or SRTM elevation data (~30 m) from USGS earth explorer (https://earthexplorer.usgs.gov/) can be identified which could help in providing additional information on areas likely to get affected which may have not been affected during past floods. Figure 23.8 shows the downloading of CartoDEM through Bhuvan portal. DEM could also be utilized to derive various hydrological layers (Fig. 23.9) like flow direction, flow accumulation, slope, aspect, and basin boundaries using freely available (http://hydrology.usu.edu/taudem/taudem5/index.html) tools like TauDEM (Terrain Analysis Using Digital Elevation Models). TauDEM is a collection of tools for the extraction of hydrological information from DEM. This hydrologic information could be further utilized for advanced analysis like hydrological modeling to get extent of inundation based on varying discharge data and generate inundation scenarios using free hydrological modeling software’s like HecRAS (http://www.hec.usace.army.mil/software/hec-ras/). HecRAS models the hydraulics of water flow through natural rivers and other channels. Apart from disaster preparedness during the disaster, the above information also could be utilized for planning long-term disaster mitigation measures and preparing disaster management strategies. In this effort archived satellite images freely available from MODIS (https://lance-modis.eosdis.nasa.gov/imagery/subsets/?project=fas&subset=FAS_India1), Landsat (https://earthexplorer.usgs.gov/), and Sentinel (https://vertex.daac.asf.alaska.edu/#) also could be accessed to prepare flood hazard zonation maps of the area. Figure 23.10 shows flood inundation extent captured from Modis Aqua image of 10 Sept. 2014 over Srinagar Valley. This one of the severest floods (Bhatt et al. 2016) could be very helpful in disaster management planning.

Fig. 23.7
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Bhuvan portal showing historic inundation (08–23 Sept. 2014) experienced in Srinagar Valley during floods of September 2014

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Fig. 23.8
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Bhuvan portal showing CartoDEM tiles highlighted (red color) over Srinagar, Jammu, and Kashmir for downloading

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Fig. 23.9
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Flowchart showing hydrological information derived from DEM

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Fig. 23.10
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Flood inundation captured from Modis Aqua image of 10 Sept 2014 over Srinagar Valley (https://lance-modis.eosdis.nasa.gov/imagery/subsets/?project=fas&subset=FAS_India1.2014253.aqua.721.250m)

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3.3 Disaster Response

Freely open data repositories and tools are very important in providing response to a disaster. For floods particularly SAR (synthetic aperture radar) data is useful because it can image the Earth through clouds and allows dynamic hydrological events like floods to be captured. Due to persistent cloud cover during monsoon season optical data does not provide much support in monitoring of flood events. Availability of SAR data since 2014 from Sentinel-1, a SAR mission from ESA, available free of charge, has equipped the disaster managers with a powerful dataset especially for flood disasters to respond to flood situation quickly than to wait for cloud-free optical data. Sentinel-1 data can be downloaded by registering at the Sentinels Scientific Data Hub (https://cophub.copernicus.eu/dhus/) and by specifying the area of interest, product type, sensor mode, and sensing period, among others (Fig. 23.11). The data can also be accessed by registering at Vertex (https://vertex.daac.asf.alaska.edu/#) which is the Alaska Satellite Facility’s data portal for remotely sensed imagery of the Earth. Through these, portals archival (before flood event) and latest (during flood event) Level-1 Ground Range Detected (GRD) Sentinel-1 data in C-band in VV and VH polarizations, which incorporates already some basic preprocessing, can be accessed for analysis. The pre- and during event Sentinel data provides (a) pre-flood river extent and waterlogged areas, and (b) present spatial extent of inundation.

Fig. 23.11
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Availability of Sentinel data over Srinagar region (area of interest) for archival and current period shown as footprint (center) and also as browse images (right side)

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For the analysis of Sentinel data, freely available tool from ESA’s Sentinel Application Platform (SNAP) can be downloaded (http://step.esa.int/main/download/) and used. The user needs to have basic to intermediate knowledge of image processing and basic knowledge of SAR theory for working with the SAR images. SNAP software can be used for preprocessing of data like calibration (calibrated values of the backscatter coefficient), speckle filtering, ortho-rectification, and thresholding. To separate water from non-water histogram of the filtered backscatter coefficient image is analyzed. Low values of the backscatter in the histogram correspond to water, and high values shall correspond to the non-water class. Sentinel 1A SAR data over Srinagar region (left panel) and water layer extracted (right panel) using SNAP software (Fig. 23.12). The classified layer can be fine-tuned using shaded relief generated from CartoDEM. Pre-flood water bodies can be extracted using similar approach from the pre-event data and can be subtracted from the classified water layer to generate the flood inundation layer. This layer then can be used in a GIS software for area computation and map composition. QGIS is a cross-platform free (http://www.qgis.org/en/site/forusers/download.html) and open-source desktop geographic information system (GIS) application that supports viewing, editing, and analysis of geospatial data (Fig. 23.13). Once the flood inundation layer is available, apart from inundated area computation, a decision-maker is also interested in knowing the roads and rail network submerged and districts affected. OpenStreetMap (OSM) which supports and enables the development of freely reusable geospatial data can be used for downloading (https://www.openstreetmap.org/) base data like roads, rail, points of interest, and administrative boundaries and can be integrated with inundation layer for flood-related analysis and map composition.

Fig. 23.12
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Sentinel 1A SAR data over Srinagar region (left panel) and water layer extracted (right panel) using SNAP software

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Fig. 23.13
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Flood layer extracted can be visualized using OpenStreetMap as plugin using QGIS

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4 Popular Geoweb Services and Online Data Repositories

This section provides a list of freely available resources like online data repositories, tools, and software that could help decision-makers in disaster monitoring and mitigation. The lists have been categorized into popular geoportal applications (Table 23.1), portal providing alerts, online data repository and natural disaster-related information (Table 23.2), other online data repositories useful for general research and analysis including disaster mitigation (Table 23.3), tools and models available in open domain for disaster analysis (Table 23.4), and freely available GIS software’s available for geographic data analysis during disasters (Table 23.5). The information and list of websites provided for free geospatial data, software, and other datasets may not be exhaustive, and the users are requested to refer and update with more web resources and the license policy of the providers.

Table 23.5 Freely available GIS software available for geographic data analysis during disasters
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5 Challenges and Gaps

Geoweb services and online open data repositories have surpassed the barrier of data availability for scientific studies in geospatial domain. Today, huge amount of geospatial data and information are available in different formats, scale, and resolution from global to local scale.

Geoweb services can bring and integrate vast amount of data from heterogeneous sources to generate effective information required to address different applications. Geospatial technology and geospatial data available in open domain today find a wider acceptance among decision-makers and planners especially for responding to disasters and other emergency events. Freely available information and tools now searchable and accessible through portals have become an important tool for decision-making process during natural disasters which have large spatial extent, affecting several people across countries and involving large number of different agencies to work in tandem. However there are still gap areas which restrict the effective use and scope of these data repositories and services. The major gaps are lack of awareness, capacity building of application user(s), and availability of network bandwidth for high-speed data transfer, online computation, algorithm development, etc. Capacity building for the development of skilled manpower who has the technical know-how about the data availability through Geoweb services, data sharing, data mining, and analysis is the major challenge that hinders the effective utilization of the technology. Internet connectivity is another major concern particularly in developing countries which prevents the full utilization of these resources. During the last decade, the data-originating organizations have come forward to share their data using geoportals and related applications, but still the data and information are available mainly for geo-visualization and querying using basic services standards such as WMS and WMTS. The data access using data service standards such WFS, WCS, WFS-T, etc. are very limited which are restricting the use of these resources by geospatial professionals. Utilization of Web Processing Services (WPS) for scientific studies is one of the exciting areas where more focus needs to be given. The WPS-based solutions provide online mode of data analysis and processing without physical download of data at user’s end.