# Remote Sensing-Based Proxies for Urban Disaster Risk Management and Resilience: A Review
## 5 Conclusions and Discussion  
This article surveyed recent advances in the development of RS-based proxies for urban DRM, focusing on the literature for both pre- and post-disaster situation assessments. Specifically, damage, recovery, vulnerability, and resilience RS-based proxies were identified along the four dimensions of built-up, economic, social, and natural environments. The structured review of 114 published articles shows that a comprehensive toolkit of RS-proxies has been developed and it is widely used in practice. We observed an increasing use in the number of proxy-based studies in urban DRM. This is due to the availability of diverse and detailed image data and rapidly increasing computational power to a growing number of communities. This also shows an increasing need for and interest in proxy-based measurements. Despite significant progress, there are gaps evident in the field that demand further research to focus on a number of directions:  
(1) A rich set of RS-based proxies currently focuses on the physical side of urban DRM. Yet, urban DRM assessments rarely go beyond aggregated proxies for the socio-economic environment and the offered proxies are very limited to assess functional aspects. For example, although a good number of proxies has been developed for building-based damage detection, none of them addresses the functionality of the buildings that is also a critical information source for all aspects of urban DRM. Assessing the extent of damage to socio-economic activities and their functional recovery is essential and will likely be possible via a complimentary set of proxies rather than a single index. (2) RS-based proxies have been developed in several different fields that can be interchangeably used for other DRM phases with little modification in estimation methodology. There are relatively few detailed proxies for recovery assessment when compared to damage assessment in built-up environments (Figure 2), whereas most of the damage assessment proxies can also be used for recovery assessment. The opposite is also true, and some of the RS-based proxies that have been developed for other environments, e.g., in the economics environment, can also be used for damage assessment. Furthermore, this statement is also correct with respect to the use of proxies for other risk elements in urban DRM: e.g., GPP that has been used for economic recovery and resilience assessments, could also be used for damage and vulnerability assessments. As a result, developing proxies that are focused on a particular risk element may overlook similar proxies, which have been developed to address the same point but under different names. Our review integrates these different streams of literature and offers a structured overview of the state-of-the-art RS methods across various DRM phases. More work on aligning methodological advancements and use of similar RS tools, data, and analysis to address DRM at various stages is vital to advance the field without reinventing the wheel. (3) Using insights from other disciplines in developing RS-based proxies offers possibilities to intelligently connect various proxies that allow to comprehensively assess vulnerability, resilience, damage, and recovery for urban DRM beyond the physical impact alone. As suggested in this review, a structured analysis of specific proxy-based examples and finding important proxies from structural engineering, economic, social and natural sciences for urban DRM will be instrumental in creating a public interdisciplinary library of methods for urban DRM. If maintained and updated by an interdisciplinary scholarly and practitioners community, such an open library, will always rely on the state-of-the-art RS data and processing methods to extract them. It will help the RS community to fill the gap in comprehensive assessments of the different DRM phases in urban settings and beyond. (4) Disaster resilience is one of the significant components of DRM, which has been gaining increasing importance in this field.