## 1 Introduction  
Situational awareness in natural disasters refers to the cognition, comprehension, and prediction of various elements in a dynamic disaster environment within specific spatial and temporal contexts [1]. Social sensing information, represented by Volunteered Geographic Information (VGI), offers advantages such as large data volumes, extensive coverage, and high spatial and temporal resolution, allowing individuals to act as \"social sensors\" [2]. Since its introduction, the definition of the term Volunteered Geographic Information (VGI) has been expanded. In this paper, we adopt the definition of VGI as introduced by [PERSON]: \"VGI is the voluntarily exchangeable information that includes any geographic and spatial information provided by the population (before, during, and after a crisis) and is available through different VGI platforms, i.e., OpenStreetMap, social media platforms, mobile applications, and more\" [3]. Social media data, as a typical form of geospatial big data, also serves as a key source of VGI. In recent years, social media has rapidly evolved, playing a crucial role in sensing disaster events. The focus of disaster monitoring has shifted from observation to perception, emphasizing the dynamics and comprehensiveness of the disaster situation. Traditional Internet of Things (IoT) sensors, such as water level sensors, are primarily used for monitoring water levels in large water bodies such as reservoirs and rivers. Although real-time results are often available from these sensors, they have limited spatial coverage and resolution, making it difficult to capture spatial heterogeneity [4]. While remote sensing imagery can monitor affected areas, it is constrained by satellite revisit cycles and weather conditions, leading to insufficient temporal resolution and challenges in accurately identifying fine details [5]. Furthermore, remote sensing cannot quickly monitor short-term disasters, while information shared by individuals online during disasters may contain real-time details about locations, types, and severity of damage, providing valuable insights for rapid disaster situation awareness [6]. During disasters, social media can be utilized for information dissemination, communication, and organizing relief efforts [7]. Although social media platforms may not provide precise measurements of physical quantities (e.g., water level height), they offer flexible coverage and strong real-time capabilities in disaster situational awareness. Social media can facilitate disaster sensing anytime and anywhere, addressing the limitations of traditional observational data in capturing societal perceptions and information. The information on social media exhibits multimodal characteristics, including various forms such as text, images, videos, and geotagging data. These multimodal data are more suitable for rapid disaster situation awareness, thereby supporting emergency management agencies in conducting rescue operations and post-disaster recovery efforts at multiple levels. Social media platforms can rapidly disseminate real-time information about disaster events, including the location, scale, and extent of impact, allowing the public to stay informed about the disaster situation. [PERSON] [8], using typhoons as an example, found that tweets during typhoon events often include information on wind and rain intensity, providing real-time reflections of the intensity of hazardous factors. [PERSON] [9] analyzed the spatiotemporal metadata extracted from images collected from social media during wildfire events and demonstrated that geotagged information helped identify areas affected by the fire. [PERSON] et al. [10] and [PERSON] et al. [11] found a strong correlation between social media activity and disaster losses. [PERSON] [12] used social media and crowdsourced data for high-resolution monitoring of urban flooding. Rescue teams can use social media to understand the needs of affected individuals and provide aid.