In case of emergency, we need to grasp the situation and make correct assessment quickly. The video data taken from monitoring cameras are important information in the emergent situation. In our research, we built a support system for identifying video data of monitoring cameras. The system collects video data from the net-cameras through the Internet and deals with them as spatio-temporal data. To search video data, we proposed an intuitive search method for users. In the method, we assume a virtual wall in the city. This method allows users to search for the video data, which is recorded during a period, and records a virtual wall in a certain direction. The users set the above search-key on the map, and it will be transformed to the searchkey for the spatio-temporal access structure to proceed the search. When the system shows the search result, the video data, which is easy to understand the whole scene, will be displayed .rst. As the horizontal direction of the screen corresponds to the virtual wall?s direction in the real world, the user can narrow down the search result in the horizontal direction of the screen. We built a prototype in Java, Javaservlet and C++.