Major disasters pose global challenges [1
] around the world not only because they typically affect large areas and can have impacts that cross national borders, but also because they typically incur considerable damages to residents, societies, and economic systems. Some disasters even require international assistance for the emergency response and relief. Annually, roughly 300 major disasters are recorded under the Centre for Research on the Epidemiology of Disasters (CRED) through its Emergency Events Database (EM-DAT) [2
]. Timely and accurate assessments of damage are critical to better understand the overall impacts of disasters and to support more scientific decision making that can guide emergency rescue, relief, and reconstruction efforts. Global open geo-information and other information drawn from multiple sources, including formats of different levels and scales based on appropriate integration approaches, could not only be used to estimate the extent of damage involved, but also to observe spatial and temporal patterns for disaster damage assessments that support disaster management in instructive and effective ways [3
Disaster assessments involve the use of dynamic processes determined based on different emergency stages, accessible data sources, and outcome accuracies, and can be divided into three types: rapid impact estimations, physical damage assessments, and comprehensive assessments. As more time passes after a disaster occurs, more sourced and detailed data can be accessed for damage assessments, thus rendering the results more accurate. Rapid impact estimations are typically conducted within hours to days following a disaster and are based on experimental approaches (e.g., the Prompt Assessment of Global Earthquake for Response (PAGER) system [4
] developed by the U.S. Geological Survey and the Global Disaster Alert and Coordination System (GDACS)) [5
] that can be used to initially determine the possible impacts for disaster managers. Comprehensive disaster assessments are conducted based on thorough and detailed datasets using multiple approaches, including ground surveys, when disaster conditions are stable and when emergency response operations are ending, which can sometimes occur after several months [6
], in turn producing accurate and thorough outcomes for further recovery and reconstruction planning. Periods of time ranging from hours to weeks or months are required for disaster rescue and emergency relief efforts when physical damage assessments are required. Populations, buildings, infrastructure, and other physical assets are the main affected elements that are assessed after a disaster. As there is typically a lack of complete post disaster information due to time limitations, physical damage assessments are conducted by integrating as much available information as possible. Satellite remote sensing methods integrated with other geo-information tools are widely used for physical damage assessments. As disaster conditions are changing at this stage, damage assessment information requirements for supporting disaster response measures are also dynamic and urgent. As more data become available with the passage of time after a disaster occurs, the accuracy and covered area of a physical damage assessment also improves.
With the development of advanced geo-information technologies and with the promotion of global open data, enormous global open geo-datasets are now accessible and could be utilized for dynamic disaster assessments when integrated with other information. Although global open source datasets are typically available at a coarser scale relative to local scale geo-datasets, they are suitable for efficient and large-scale damage estimations as they are created in standard formats and are easily accessible. The existing global dataset with information on elements for disaster assessment includes hazard, exposure, post-disaster, and auxiliary data. The Global Land Cover (GLC) map is a widely used global open dataset that could be employed as a source of disaster exposure data. A number of medium resolution (300–1000 m) GLC maps have been developed over the last two decades [8
]. With the development of open satellite archives and large data processing and storage tools, higher resolution (less than 30 m) GLP maps such as Globeland30 [9
] have been produced since 2013 [11
]. Global settlement mapping products such as GUF and GHSL datasets have been created at an unprecedented spatial resolution of 12 m [12
]. Such high-resolution GLC mapping products will greatly improve accuracy levels and timelines when used for disaster damage assessment, and especially when applied for countries lacking a uniform national exposure dataset. Such products will also dramatically facilitate international cooperation in emergency mapping for major disasters.
Global geo-information has been used for major disaster dynamic assessments in conjunction with other information for data accessing, information analysis, and product use, in consultation with corresponding policies, standards, platforms, and cooperation initiatives. In total, 75 countries have joined the Open Government Partnership [13
] for open government data use for various purposes (e.g., for disaster emergencies with guidance from the Open Data Charter of 2015) [14
]. Within the framework of the International Charter on “Space and Major Disasters”, more than 40 operational earth observation satellites with a variety of optical or synthetic aperture radar (SAR) sensors can be mobilized and tasked to acquire earth observation data of a disaster affected area during the major disaster emergency stage [15
]. Through its Common Infrastructure (GCI), GEOSS links existing and planned spatial information resources and provides access to existing databases and portals through the ‘GEOSS Portal’ for decision makers and emergency managers [16
]. The European community (INSPIRE) also promotes open access to such data for disaster management purposes through structured and standardized data management initiatives. The European Copernicus Programme not only openly provides sentinel satellite images, but also emergency mapping services. The United Nations Space-based Information for Disaster Management and Emergency Response (UN-SPIDER) and Operational Satellite Applications (UNOSAT) Programmes, as well as other initiatives, have been developed to deliver spatial information services for disaster risk reduction and emergency responses.
Despite these efforts, gaps still exist between the information required and its availability, especially in regards to damage assessments. For instance, while it can take days to months to acquire post disaster information covering an entire affected area either through survey or earth observation approaches, disaster managers need this information in almost real time. Existing information is occasionally available from various agencies in different formats, and interoperability issues can result due to a lack of standardized formats, methodologies, and sharing mechanisms. The Sendai Framework for Disaster Risk Reduction: 2015–2030 [17
] (adopted at the third UN world conference held in Sendai, Japan, on 18 March 2015) makes use of existing space and geo-information through open data promotion and international cooperation. Geo-information could be integrated at global and local levels to address gaps in information affecting disaster damage assessments, while expanding global open datasets. In this paper, available global open geo-information and the framework of dynamic disaster assessment approaches are reviewed and elaborated on. A major flood occurring in Myanmar from July to August 2015 is taken as a study case. Damages are dynamically estimated from global open geo-information, earth observation images, and other information. The paper also presents challenges and perspectives related to integrating multi-sourced geo-information for damage assessments in a consideration of past and current developments in this domain.