Technological advancements in smart cities are a global trend, primarily focused on enhancing the quality of life for citizens while also monitoring urban environments. Viewing smart cities as urban surveillance platforms, there arises a pressing need for efficient analysis and storage of video streams from numerous cameras scattered across the city, owned by various stakeholders. However, surveillance systems face several internet of things (IoT) challenges, including privacy concerns, scalability issues, and substantial energy consumption. To tackle these challenges, the development of a trusted video surveillance system by integrating the internet of spatial things (IoST) with fog computing and blockchain technology was introduced. Fog nodes are strategically deployed at the network's edge, enabling the extension of cloud services closer to the data source. This deployment strategy aims to reduce latency and alleviate network congestion. At these fog nodes, the system employs a proof-of-work-based consensus algorithm, encrypted using the secure hash algorithm (SHA-256), to ensure data trust and reliability within the blockchain infrastructure supporting the surveillance system. The evaluation of our proposed blockchain-IoST surveillance system involves a comparison of two case studies: one based on fog computing and the other on traditional cloud-based blockchain-IoST implementations, conducted within the iFogSim framework. Furthermore, the system's scalability is tested under various scenarios. To assess the effectiveness of our methodology in mitigating latency, optimizing network utilization, and reducing energy consumption, we conducted comprehensive simulations. The results of our experiments clearly demonstrate the advantages of the fog-based blockchain-IoST approach. This approach significantly reduces latency and network utilization when compared to the conventional cloud-based blockchain-IoST implementation in the trusted video surveillance system. Additionally, the findings indicate that adopting the fog-based blockchain-IoST approach leads to a noteworthy reduction in energy consumption compared to the cloud-based implementation, further enhancing the sustainability and efficiency of the surveillance system.